Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

In article ,
"Ian Field" wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

It's common to use the output to drive the timing circuit on 555
variations with rail-to-rail output. The discharge pin's maximum
voltage varies by part number and it's sometimes very low.

Why not flip the shut regulator around so the 555 shares a common rail
with the MOSFET?
--
I will not see posts from Google or e-mails from Yahoo because I must
filter them as spam

"Kevin McMurtrie" wrote in message
...
In article ,
"Ian Field" wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

It's common to use the output to drive the timing circuit on 555
variations with rail-to-rail output. The discharge pin's maximum
voltage varies by part number and it's sometimes very low.

Why not flip the shut regulator around so the 555 shares a common rail
with the MOSFET?

Because I'd need something a bit sturdier than a resistor/zener to get the
current I want from the MOSFET pair.

On Sat, 26 Mar 2011 16:24:03 -0000, "Ian Field"
wrote:


"Kevin McMurtrie" wrote in message
.. .
In article ,
"Ian Field" wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

It's common to use the output to drive the timing circuit on 555
variations with rail-to-rail output. The discharge pin's maximum
voltage varies by part number and it's sometimes very low.

Why not flip the shut regulator around so the 555 shares a common rail
with the MOSFET?

Because I'd need something a bit sturdier than a resistor/zener to get the
current I want from the MOSFET pair.


But you'll need a resistive pull-up from the discharge transistor,
probably giving you more over-lap current in your output than you'll
want.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Remember: Once you go over the hill, you pick up speed

"Jim Thompson" wrote in
message ...
On Sat, 26 Mar 2011 16:24:03 -0000, "Ian Field"
wrote:


"Kevin McMurtrie" wrote in message
. ..
In article ,
"Ian Field" wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple
resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel
MOSFET.

Thanks.

It's common to use the output to drive the timing circuit on 555
variations with rail-to-rail output. The discharge pin's maximum
voltage varies by part number and it's sometimes very low.

Why not flip the shut regulator around so the 555 shares a common rail
with the MOSFET?

Because I'd need something a bit sturdier than a resistor/zener to get the
current I want from the MOSFET pair.


But you'll need a resistive pull-up from the discharge transistor,

That seemed to me to be so obvious that I didn't need to point it out to
anyone!

probably giving you more over-lap current in your output than you'll
want.


Maybe - I'll just have to prototype it and see how hot it gets.

Ian Field wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the source/sink output won't go high enough to cut off the P-channel
MOSFET.

Do you have a schematic you can post? It's a little hard for me to
understand your description, but you know a picture is worth a thousand
words. :-)

But from what I can get from your description, it sounds like you might
want another zener to clamp your feedback voltage; not sure what that
would do with your circuit operation, however.

Thanks,
Rich

"Rich Grise" wrote in message
...
Ian Field wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the source/sink output won't go high enough to cut off the P-channel
MOSFET.

Do you have a schematic you can post? It's a little hard for me to
understand your description, but you know a picture is worth a thousand
words. :-)

But from what I can get from your description, it sounds like you might
want another zener to clamp your feedback voltage; not sure what that
would do with your circuit operation, however.


Feedback voltage???

"Rich Grise" wrote in message
...
Ian Field wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the source/sink output won't go high enough to cut off the P-channel
MOSFET.

Do you have a schematic you can post? It's a little hard for me to
understand your description, but you know a picture is worth a thousand
words. :-)


Well I suppose I can draw pictures for you if you really need it - but I
have to re-install my scanner because I never got around to it since the
last MOBO upgrade.

Lets say pin 7 has a 1k pull up to Vcc - AFAIK pin 3 & pin 7 will then rise
and fall in the same phase, this means that they can be interchanged if the
situation warrants it.

Since I want to drive a complementary pair of MOSFETs which have a higher
Vdd than Vcc, pin 3 won't rise high enough to cut off the P-channel MOSFET -
however; if I pull up pin 7 to Vdd it will.


If you're still confused maybe you should chose a less technical subject.

Ian Field wrote:

If you're still confused maybe you should chose a less technical subject.

Or if you're going to insult people who are trying to help you, maybe you
should go **** yourself.

Good Luck!
Rich

"Rich Grise" wrote in message
...
Ian Field wrote:

If you're still confused maybe you should chose a less technical subject.

Or if you're going to insult people who are trying to help you, maybe you
should go **** yourself.

Good Luck!
Rich


You might have convinced yourself you were trying to help but that's not the
way it looked when I read it.

On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

---
If you use a CMOS 555 you can drive the timing RC directly from the
555's OUTPUT pin, as well as the gates of your complementary pair.

Something like this:

Version 4
SHEET 1 1476 884
WIRE -256 -64 -1008 -64
WIRE -16 -64 -256 -64
WIRE 128 -64 -16 -64
WIRE -16 -16 -16 -64
WIRE 128 32 128 -64
WIRE -16 112 -16 64
WIRE 80 112 -16 112
WIRE -160 208 -624 208
WIRE -128 208 -160 208
WIRE -16 208 -16 112
WIRE -16 208 -48 208
WIRE -1008 288 -1008 -64
WIRE -880 288 -1008 288
WIRE -736 288 -784 288
WIRE -512 288 -736 288
WIRE -192 288 -288 288
WIRE -624 304 -624 208
WIRE 128 320 128 128
WIRE 272 320 128 320
WIRE -224 352 -288 352
WIRE -1008 400 -1008 288
WIRE -960 400 -1008 400
WIRE -832 400 -832 352
WIRE -832 400 -880 400
WIRE -624 416 -624 384
WIRE -512 416 -624 416
WIRE -160 416 -160 208
WIRE -160 416 -288 416
WIRE 272 448 272 320
WIRE -832 464 -832 400
WIRE -736 464 -736 288
WIRE -256 480 -256 -64
WIRE -256 480 -288 480
WIRE 128 528 128 320
WIRE -16 544 -16 208
WIRE 80 544 -16 544
WIRE -1008 576 -1008 400
WIRE -624 576 -624 416
WIRE -224 576 -224 352
WIRE -224 576 -624 576
WIRE -16 592 -16 544
WIRE -624 608 -624 576
WIRE -1008 720 -1008 656
WIRE -832 720 -832 528
WIRE -832 720 -1008 720
WIRE -736 720 -736 528
WIRE -736 720 -832 720
WIRE -624 720 -624 672
WIRE -624 720 -736 720
WIRE -192 720 -192 288
WIRE -192 720 -624 720
WIRE -16 720 -16 672
WIRE -16 720 -192 720
WIRE 128 720 128 624
WIRE 128 720 -16 720
WIRE 272 720 272 528
WIRE 272 720 128 720
WIRE -1008 784 -1008 720
FLAG -1008 784 0
SYMBOL voltage -1008 560 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value 24
SYMBOL res 256 432 R0
SYMATTR InstName R1
SYMATTR Value 10
SYMBOL nmos 80 32 R0
SYMATTR InstName M1
SYMATTR Value FDS6699S
SYMBOL pmos 80 624 M180
SYMATTR InstName M2
SYMATTR Value HAT1072H
SYMBOL res -32 -32 R0
SYMATTR InstName R6
SYMATTR Value 2000
SYMBOL res -32 576 R0
SYMATTR InstName R8
SYMATTR Value 2000
SYMBOL Misc\\NE555 -400 384 M0
SYMATTR InstName U2
SYMBOL res -608 288 M0
SYMATTR InstName R3
SYMATTR Value 19.8k
SYMBOL cap -608 608 M0
WINDOW 0 -33 32 Left 0
WINDOW 3 -39 58 Left 0
SYMATTR InstName C1
SYMATTR Value 1E-7
SYMBOL zener -816 528 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value BZX84C15L
SYMBOL res -864 384 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 300
SYMBOL cap -752 464 R0
SYMATTR InstName C2
SYMATTR Value 10e-6
SYMBOL npn -880 352 R270
SYMATTR InstName Q1
SYMATTR Value 2N2222
SYMBOL res -32 192 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R4
SYMATTR Value 200
TEXT -808 744 Right 0 !.tran .1 startup uic
TEXT -280 272 Left 0 ;1
TEXT -280 336 Left 0 ;2
TEXT -280 400 Left 0 ;3
TEXT -280 456 Left 0 ;4
TEXT -536 456 Left 0 ;5
TEXT -536 400 Left 0 ;6
TEXT -536 336 Left 0 ;7
TEXT -536 272 Left 0 ;8

--
JF

"John Fields" wrote in message
...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

---
If you use a CMOS 555 you can drive the timing RC directly from the
555's OUTPUT pin, as well as the gates of your complementary pair.


It looks as if you've completely missed the point - I can't drive the
MOSFETs from the O/P pin because Vdd will be higher than Vcc.

If I put the pin 7 pull up resistor to Vdd it can pull up high enough to cut
off the P-channel but since pin 7 now swings higher than Vcc it might not be
a good idea to also apply it to pins 2 & 6.

There are application examples around of a 555 wired this way, and I may
even have some if I could remember where.

I was asking if anyone had or knew where I could get some application
examples - but apparently not!

On Sat, 26 Mar 2011 21:24:48 -0000, "Ian Field"
wrote:


"John Fields" wrote in message
.. .
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

---
If you use a CMOS 555 you can drive the timing RC directly from the
555's OUTPUT pin, as well as the gates of your complementary pair.


It looks as if you've completely missed the point - I can't drive the
MOSFETs from the O/P pin because Vdd will be higher than Vcc.

If I put the pin 7 pull up resistor to Vdd it can pull up high enough to cut
off the P-channel but since pin 7 now swings higher than Vcc it might not be
a good idea to also apply it to pins 2 & 6.

There are application examples around of a 555 wired this way, and I may
even have some if I could remember where.

I was asking if anyone had or knew where I could get some application
examples - but apparently not!


What is the threshold voltages of your NMOS and your PMOS?

VCC and VDD values?

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Remember: Once you go over the hill, you pick up speed

"Jim Thompson" wrote in
message ...
On Sat, 26 Mar 2011 21:24:48 -0000, "Ian Field"
wrote:


"John Fields" wrote in message
. ..
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

---
If you use a CMOS 555 you can drive the timing RC directly from the
555's OUTPUT pin, as well as the gates of your complementary pair.


It looks as if you've completely missed the point - I can't drive the
MOSFETs from the O/P pin because Vdd will be higher than Vcc.

If I put the pin 7 pull up resistor to Vdd it can pull up high enough to
cut
off the P-channel but since pin 7 now swings higher than Vcc it might not
be
a good idea to also apply it to pins 2 & 6.

There are application examples around of a 555 wired this way, and I may
even have some if I could remember where.

I was asking if anyone had or knew where I could get some application
examples - but apparently not!


What is the threshold voltages of your NMOS and your PMOS?

VCC and VDD values?


The P-channel states from 2 to 4V, the complement is probably slightly
better.

As I stated in my original post the circuit will be powered by any handy
wall wart at least 12V - on light loads this could rise as high as 20V with
unregulated iron-cored wall-warts.

Vcc for the 555 will be regulated with a resistor/zener - some app notes I
read recently say abs-max 16V, but I remember using a Hitachi 555 a while
back for which thair data sheet said 18V.

On Sat, 26 Mar 2011 21:58:25 -0000, "Ian Field"
wrote:


"Jim Thompson" wrote in
message ...
On Sat, 26 Mar 2011 21:24:48 -0000, "Ian Field"
wrote:


"John Fields" wrote in message
...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

---
If you use a CMOS 555 you can drive the timing RC directly from the
555's OUTPUT pin, as well as the gates of your complementary pair.


It looks as if you've completely missed the point - I can't drive the
MOSFETs from the O/P pin because Vdd will be higher than Vcc.

If I put the pin 7 pull up resistor to Vdd it can pull up high enough to
cut
off the P-channel but since pin 7 now swings higher than Vcc it might not
be
a good idea to also apply it to pins 2 & 6.

There are application examples around of a 555 wired this way, and I may
even have some if I could remember where.

I was asking if anyone had or knew where I could get some application
examples - but apparently not!


What is the threshold voltages of your NMOS and your PMOS?

VCC and VDD values?


The P-channel states from 2 to 4V, the complement is probably slightly
better.

As I stated in my original post the circuit will be powered by any handy
wall wart at least 12V - on light loads this could rise as high as 20V with
unregulated iron-cored wall-warts.

Vcc for the 555 will be regulated with a resistor/zener - some app notes I
read recently say abs-max 16V, but I remember using a Hitachi 555 a while
back for which thair data sheet said 18V.


Why does your wall-wart have such lousy regulation?

Study the output stage of...

http://analog-innovations.com/SED/MC1554-DataSheet.pdf

for how to do your driver (lower portion would be the discharge device
from the 555 timer; and you probably don't need Darlington).

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Remember: Once you go over the hill, you pick up speed

On Sat, 26 Mar 2011 21:24:48 -0000, "Ian Field"
wrote:


"John Fields" wrote in message
.. .
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

---
If you use a CMOS 555 you can drive the timing RC directly from the
555's OUTPUT pin, as well as the gates of your complementary pair.


It looks as if you've completely missed the point - I can't drive the
MOSFETs from the O/P pin because Vdd will be higher than Vcc.

---
Yup...

Sorry 'bout that. :-(
---

If I put the pin 7 pull up resistor to Vdd it can pull up high enough to cut
off the P-channel but since pin 7 now swings higher than Vcc it might not be
a good idea to also apply it to pins 2 & 6.

There are application examples around of a 555 wired this way, and I may
even have some if I could remember where.

I was asking if anyone had or knew where I could get some application
examples - but apparently not!

---
Try this:

Version 4
SHEET 1 1476 884
WIRE -256 -96 -1008 -96
WIRE -48 -96 -256 -96
WIRE 160 -96 -48 -96
WIRE 304 -96 160 -96
WIRE -48 -48 -48 -96
WIRE 304 48 304 -96
WIRE 160 64 160 -96
WIRE -48 80 -48 32
WIRE 64 80 -48 80
WIRE 112 80 64 80
WIRE -48 112 -48 80
WIRE -704 160 -752 160
WIRE -576 160 -624 160
WIRE -112 160 -576 160
WIRE -160 224 -624 224
WIRE 160 256 160 160
WIRE 304 256 304 128
WIRE 304 256 160 256
WIRE -1008 288 -1008 -96
WIRE -880 288 -1008 288
WIRE -752 288 -752 160
WIRE -752 288 -784 288
WIRE -736 288 -752 288
WIRE -512 288 -736 288
WIRE -192 288 -288 288
WIRE -624 304 -624 224
WIRE -576 352 -576 160
WIRE -512 352 -576 352
WIRE -224 352 -288 352
WIRE -1008 400 -1008 288
WIRE -960 400 -1008 400
WIRE -832 400 -832 352
WIRE -832 400 -880 400
WIRE -624 416 -624 384
WIRE -512 416 -624 416
WIRE -160 416 -160 224
WIRE -160 416 -288 416
WIRE 160 416 160 256
WIRE 304 448 304 256
WIRE -832 464 -832 400
WIRE -736 464 -736 288
WIRE -256 480 -256 -96
WIRE -256 480 -288 480
WIRE 64 496 64 80
WIRE 112 496 64 496
WIRE -624 544 -624 416
WIRE -224 544 -224 352
WIRE -224 544 -624 544
WIRE -1008 576 -1008 400
WIRE -624 576 -624 544
WIRE -1008 688 -1008 656
WIRE -832 688 -832 528
WIRE -832 688 -1008 688
WIRE -736 688 -736 528
WIRE -736 688 -832 688
WIRE -624 688 -624 640
WIRE -624 688 -736 688
WIRE -192 688 -192 288
WIRE -192 688 -624 688
WIRE -48 688 -48 208
WIRE -48 688 -192 688
WIRE 160 688 160 512
WIRE 160 688 -48 688
WIRE 304 688 304 528
WIRE 304 688 160 688
WIRE -1008 752 -1008 688
FLAG -1008 752 0
SYMBOL voltage -1008 560 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 0 16 7 Left 0
WINDOW 3 16 99 Left 0
SYMATTR InstName V2
SYMATTR Value 24
SYMBOL res 288 432 R0
SYMATTR InstName R1
SYMATTR Value 10
SYMBOL nmos 112 416 R0
SYMATTR InstName M1
SYMATTR Value FDS6699S
SYMBOL pmos 112 160 M180
SYMATTR InstName M2
SYMATTR Value HAT1072H
SYMBOL Misc\\NE555 -400 384 M0
SYMATTR InstName U2
SYMBOL res -608 288 M0
SYMATTR InstName R3
SYMATTR Value 20K
SYMBOL cap -608 576 M0
WINDOW 0 -33 32 Left 0
WINDOW 3 -39 58 Left 0
SYMATTR InstName C1
SYMATTR Value 1E-7
SYMBOL zener -816 528 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value BZX84C15L
SYMBOL res -864 384 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 470
SYMBOL npn -880 352 R270
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL polcap -752 464 R0
SYMATTR InstName C3
SYMATTR Value 10e-6
SYMBOL res -64 -64 R0
SYMATTR InstName R4
SYMATTR Value 1K
SYMBOL npn -112 112 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL res 288 32 R0
SYMATTR InstName R6
SYMATTR Value 10
SYMBOL res -608 144 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R7
SYMATTR Value 10K
TEXT -776 720 Right 0 !.tran .05 startup uic
TEXT -280 272 Left 0 ;1
TEXT -280 336 Left 0 ;2
TEXT -280 400 Left 0 ;3
TEXT -280 456 Left 0 ;4
TEXT -536 456 Left 0 ;5
TEXT -536 400 Left 0 ;6
TEXT -536 336 Left 0 ;7
TEXT -536 272 Left 0 ;8
TEXT 88 120 Left 0 ;P
TEXT 88 464 Left 0 ;N
TEXT 376 88 Left 0 ;SINK LOAD
TEXT 368 488 Left 0 ;SOURCE LOAD


--
JF

On Sat, 26 Mar 2011 20:01:05 -0500, John Fields
wrote:

On Sat, 26 Mar 2011 21:24:48 -0000, "Ian Field"
wrote:


"John Fields" wrote in message
. ..
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.

---
If you use a CMOS 555 you can drive the timing RC directly from the
555's OUTPUT pin, as well as the gates of your complementary pair.


It looks as if you've completely missed the point - I can't drive the
MOSFETs from the O/P pin because Vdd will be higher than Vcc.

---
Yup...

Sorry 'bout that. :-(
---

If I put the pin 7 pull up resistor to Vdd it can pull up high enough to cut
off the P-channel but since pin 7 now swings higher than Vcc it might not be
a good idea to also apply it to pins 2 & 6.

There are application examples around of a 555 wired this way, and I may
even have some if I could remember where.

I was asking if anyone had or knew where I could get some application
examples - but apparently not!

---
Try this:

---
Oops...
_____
RESET needs to go to Vcc; try this instead:

Version 4
SHEET 1 1476 884
WIRE -48 -96 -1008 -96
WIRE 160 -96 -48 -96
WIRE 304 -96 160 -96
WIRE -48 -48 -48 -96
WIRE 304 48 304 -96
WIRE 160 64 160 -96
WIRE -48 80 -48 32
WIRE 64 80 -48 80
WIRE 112 80 64 80
WIRE -48 112 -48 80
WIRE -704 160 -752 160
WIRE -576 160 -624 160
WIRE -112 160 -576 160
WIRE -160 224 -624 224
WIRE 160 256 160 160
WIRE 304 256 304 128
WIRE 304 256 160 256
WIRE -1008 288 -1008 -96
WIRE -880 288 -1008 288
WIRE -752 288 -752 160
WIRE -752 288 -784 288
WIRE -736 288 -752 288
WIRE -512 288 -736 288
WIRE -192 288 -288 288
WIRE -624 304 -624 224
WIRE -576 352 -576 160
WIRE -512 352 -576 352
WIRE -224 352 -288 352
WIRE -1008 400 -1008 288
WIRE -960 400 -1008 400
WIRE -832 400 -832 352
WIRE -832 400 -880 400
WIRE -624 416 -624 384
WIRE -512 416 -624 416
WIRE -160 416 -160 224
WIRE -160 416 -288 416
WIRE 160 416 160 256
WIRE 304 448 304 256
WIRE -832 464 -832 400
WIRE -256 480 -288 480
WIRE 64 496 64 80
WIRE 112 496 64 496
WIRE -736 544 -736 288
WIRE -256 544 -256 480
WIRE -256 544 -736 544
WIRE -1008 576 -1008 400
WIRE -624 576 -624 416
WIRE -224 576 -224 352
WIRE -224 576 -624 576
WIRE -736 608 -736 544
WIRE -624 608 -624 576
WIRE -1008 688 -1008 656
WIRE -832 688 -832 528
WIRE -832 688 -1008 688
WIRE -736 688 -736 672
WIRE -736 688 -832 688
WIRE -624 688 -624 672
WIRE -624 688 -736 688
WIRE -192 688 -192 288
WIRE -192 688 -624 688
WIRE -48 688 -48 208
WIRE -48 688 -192 688
WIRE 160 688 160 512
WIRE 160 688 -48 688
WIRE 304 688 304 528
WIRE 304 688 160 688
WIRE -1008 752 -1008 688
FLAG -1008 752 0
SYMBOL voltage -1008 560 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 0 16 7 Left 0
WINDOW 3 16 99 Left 0
SYMATTR InstName V2
SYMATTR Value 24
SYMBOL res 288 432 R0
SYMATTR InstName R1
SYMATTR Value 10
SYMBOL nmos 112 416 R0
SYMATTR InstName M1
SYMATTR Value FDS6699S
SYMBOL pmos 112 160 M180
SYMATTR InstName M2
SYMATTR Value HAT1072H
SYMBOL Misc\\NE555 -400 384 M0
SYMATTR InstName U2
SYMBOL res -608 288 M0
SYMATTR InstName R3
SYMATTR Value 20K
SYMBOL cap -608 608 M0
WINDOW 0 -33 32 Left 0
WINDOW 3 -39 58 Left 0
SYMATTR InstName C1
SYMATTR Value 1E-7
SYMBOL zener -816 528 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value BZX84C15L
SYMBOL res -864 384 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 470
SYMBOL npn -880 352 R270
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL polcap -752 608 R0
SYMATTR InstName C3
SYMATTR Value 10e-6
SYMBOL res -64 -64 R0
SYMATTR InstName R4
SYMATTR Value 1K
SYMBOL npn -112 112 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL res 288 32 R0
SYMATTR InstName R6
SYMATTR Value 10
SYMBOL res -608 144 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R7
SYMATTR Value 10K
TEXT -776 720 Right 0 !.tran .05 startup uic
TEXT -280 272 Left 0 ;1
TEXT -280 336 Left 0 ;2
TEXT -280 400 Left 0 ;3
TEXT -280 456 Left 0 ;4
TEXT -536 456 Left 0 ;5
TEXT -536 400 Left 0 ;6
TEXT -536 336 Left 0 ;7
TEXT -536 272 Left 0 ;8
TEXT 88 120 Left 0 ;P
TEXT 88 464 Left 0 ;N
TEXT 376 88 Left 0 ;SINK LOAD
TEXT 368 488 Left 0 ;SOURCE LOAD



--
JF

Ian Field wrote:

It looks as if you've completely missed the point - I can't drive the
MOSFETs from the O/P pin because Vdd will be higher than Vcc.

You can drive it from the output _pin_, just not from the output
of the MOSFETS. This is because Vcc == Vcc. ;-) If you're afraid
the input will drag down the gates of the output MOSFETS, slap a
resistor in there, maybe with a speedup capacitor. 10 pf ~ 1 nf,
the value shouldn't be very critical at all.

Hope This Helps!

At least you apologized for being such a poopy-head the last time
I tried to help.

Cheers!
Rich

"Rich Grise" wrote in message
...
Ian Field wrote:

It looks as if you've completely missed the point - I can't drive the
MOSFETs from the O/P pin because Vdd will be higher than Vcc.

You can drive it from the output _pin_, just not from the output
of the MOSFETS. This is because Vcc == Vcc. ;-) If you're afraid
the input will drag down the gates of the output MOSFETS, slap a
resistor in there, maybe with a speedup capacitor. 10 pf ~ 1 nf,
the value shouldn't be very critical at all.

Hope This Helps!

At least you apologized

You're delusional!

Ian Field wrote:

"Rich Grise" wrote in message
...
Ian Field wrote:

It looks as if you've completely missed the point - I can't drive the
MOSFETs from the O/P pin because Vdd will be higher than Vcc.

You can drive it from the output _pin_, just not from the output
of the MOSFETS. This is because Vcc == Vcc. ;-) If you're afraid
the input will drag down the gates of the output MOSFETS, slap a
resistor in there, maybe with a speedup capacitor. 10 pf ~ 1 nf,
the value shouldn't be very critical at all.

Hope This Helps!

At least you apologized

You're delusional!


What else is new?


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

On Sat, 26 Mar 2011 13:19:02 +0000, Ian Field wrote:

Does anyone have any application examples of the 555 with the
source/sink O/P used to drive the timing resistor and the discharge
transistor driving the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P buffer, it will run from any wall wart over 12V that could
potentially exceed the 555 ABS-MAX Vcc, so the 555 will have a simple
resistor/zener regulator, the Vdd for the MOSFETs will be the full
unregulated rail so the source/sink output won't go high enough to cut
off the P-channel MOSFET.



You may find that the voltage on pin 7 can't exceed that on pin 8 because
of the way that the discharge transistor is formed on the chip, giving a
reverse-biased diode across those pins. I'm only guessing though.

The SE555 (not the SE555C) is specified up to 18V.

The CMOS version comes with this warning (about input pins really, I
think):
NOTES:
1. Due to the SCR structure inherent in the CMOS process used to
fabricate these devices, connecting any terminal to a voltage greater than
VDD + 0.3V or less than GND -0.3V may cause destructive latch-up. For
this reason it is recommended that no inputs from external sources
not operating from the same power supply be applied to the device before
its power supply is established. In multiple systems, the supply of
the ICM7555 must be turned on first.


Nice data sheet, but perhaps not what you want:
http://www.williamson-labs.com/555_apps.htm

I think I've found what you are looking for:
http://www.555-timer-circuits.com/si...scillator.html
A pull-up on pin 7 should give another square wave, I think. As I said
though, I doubt if you can pull it up above pin 8.

Oh - get a stabilized wall wart or include a reg!

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

"mick" wrote in message
eb.com...
On Sat, 26 Mar 2011 13:19:02 +0000, Ian Field wrote:

Does anyone have any application examples of the 555 with the
source/sink O/P used to drive the timing resistor and the discharge
transistor driving the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P buffer, it will run from any wall wart over 12V that could
potentially exceed the 555 ABS-MAX Vcc, so the 555 will have a simple
resistor/zener regulator, the Vdd for the MOSFETs will be the full
unregulated rail so the source/sink output won't go high enough to cut
off the P-channel MOSFET.



You may find that the voltage on pin 7 can't exceed that on pin 8 because
of the way that the discharge transistor is formed on the chip, giving a
reverse-biased diode across those pins. I'm only guessing though.


Years ago I built a NiCd pulse charger which used a 555 purely as a window
comparator & R/S latch, pin 7 fed the gate of a triac to pulse it -ve WRT
MT2.

The charger was a real brute force & ignorance design with the charging
current supplied by a bridge rectifier interposed in the neutral lead of a
table top oven.

It did eventually fail after nearly a year of continuous use, I'm pretty
sure that pin 7 got at least spikes well in excess of Vcc and I'm fairly
sure another part of the circuit failed anyway.

On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.

Thus you're stuck with building a translator.

OR shunt regulate your cheap wall-wart by providing a minimum load :-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Remember: Once you go over the hill, you pick up speed

I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.

Thus you're stuck with building a translator.

OR shunt regulate your cheap wall-wart by providing a minimum load :-)

...Jim Thompson

My lord, how expensive can a 78L05 be?

Jim

"RST Engineering" wrote in message
...

I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.

Thus you're stuck with building a translator.

OR shunt regulate your cheap wall-wart by providing a minimum load :-)

...Jim Thompson

My lord, how expensive can a 78L05 be?


Cheap as chips and I have boxes of them - pity the voltage is too low for
the required Vdd and they won't handle enough current.

On Sun, 27 Mar 2011 18:22:01 +0100, "Ian Field"
wrote:


"RST Engineering" wrote in message
.. .

I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.

Thus you're stuck with building a translator.

OR shunt regulate your cheap wall-wart by providing a minimum load :-)

...Jim Thompson

My lord, how expensive can a 78L05 be?


Cheap as chips and I have boxes of them - pity the voltage is too low for
the required Vdd and they won't handle enough current.


How much load current must you draw from your wall wart to keep it at
16V or less?

I just fired up a 5V/1A wall wart... 5.23V at no load. (Admittedly
it's not a CHEAP wall wart.)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Remember: Once you go over the hill, you pick up speed

"Jim Thompson" wrote in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open collector
transistor - assuming that's accurate the only constraint is its collector
breakdown voltage.

On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open collector
transistor - assuming that's accurate the only constraint is its collector
breakdown voltage.


Wrong. Open collector transistor with a HIGH (relatively) resistance
path from base to ground, so turn off will be slow and subject to
snap-back into BVCEO. If that discharge device had an active turn-off
pull-down on its base I'd agree that breakdown might approach BVCBO...
but it doesn't.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Remember: Once you go over the hill, you pick up speed

"Jim Thompson" wrote in
message news
On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote
in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open collector
transistor - assuming that's accurate the only constraint is its collector
breakdown voltage.


Wrong. Open collector transistor with a HIGH (relatively) resistance
path from base to ground, so turn off will be slow and subject to
snap-back into BVCEO. If that discharge device had an active turn-off
pull-down on its base I'd agree that breakdown might approach BVCBO...
but it doesn't.


Ask a simple question - get a deluge of critisicm!

On Sun, 27 Mar 2011 18:24:32 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote in
message news
On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote
in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open collector
transistor - assuming that's accurate the only constraint is its collector
breakdown voltage.


Wrong. Open collector transistor with a HIGH (relatively) resistance
path from base to ground, so turn off will be slow and subject to
snap-back into BVCEO. If that discharge device had an active turn-off
pull-down on its base I'd agree that breakdown might approach BVCBO...
but it doesn't.


Ask a simple question - get a deluge of critisicm!


Look, you fricking little asshole... you asked, I told you the facts.
If you consider facts as criticism, then go **** yourself.

You've done gone and deprived a village of an idiot ;-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Remember: Once you go over the hill, you pick up speed

On Sun, 27 Mar 2011 18:10:15 +0100, Ian Field wrote:

"Jim Thompson" wrote
in message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink O/P used to drive the timing resistor and the discharge
transistor driving the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P buffer, it will run from any wall wart over 12V that could
potentially exceed the 555 ABS-MAX Vcc, so the 555 will have a simple
resistor/zener regulator, the Vdd for the MOSFETs will be the full
unregulated rail so the
source/sink output won't go high enough to cut off the P-channel
MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open
collector transistor - assuming that's accurate the only constraint is
its collector breakdown voltage.


That would be true if it was built using discrete bits. The trouble is
that the transistor is probably formed on a substrate at the same time as
all the others. That would imply, at the very least, that the breakdown
voltage of all the transistors on the chip would be the same. As it isn't
specified to do anything other than discharge the timing capacitor then
there isn't any need to give it a higher rating than 2/3 Vcc really.

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

"mick" wrote in message
eb.com...
On Sun, 27 Mar 2011 18:10:15 +0100, Ian Field wrote:

"Jim Thompson" wrote
in message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink O/P used to drive the timing resistor and the discharge
transistor driving the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P buffer, it will run from any wall wart over 12V that could
potentially exceed the 555 ABS-MAX Vcc, so the 555 will have a simple
resistor/zener regulator, the Vdd for the MOSFETs will be the full
unregulated rail so the
source/sink output won't go high enough to cut off the P-channel
MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open
collector transistor - assuming that's accurate the only constraint is
its collector breakdown voltage.


That would be true if it was built using discrete bits. The trouble is
that the transistor is probably formed on a substrate at the same time as
all the others. That would imply, at the very least, that the breakdown
voltage of all the transistors on the chip would be the same. As it isn't
specified to do anything other than discharge the timing capacitor then
there isn't any need to give it a higher rating than 2/3 Vcc really.


Fair point (you must be new here!) looks like I'm going to have to design
some bench tests to determine what that transistor can take without failing.

On Sun, 27 Mar 2011 12:53:35 -0500, flipper wrote:

On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the source/sink
O/P used to drive the timing resistor and the discharge transistor driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open collector
transistor - assuming that's accurate the only constraint is its collector
breakdown voltage.


I don't understand why you don't just stick an appropriately rated OC
transistor on OUT and be done with it.

That would add an inversion, but I'm unsure if it would matter in the
OP's application.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Remember: Once you go over the hill, you pick up speed

"Jim Thompson" wrote in
message ...
On Sun, 27 Mar 2011 12:53:35 -0500, flipper wrote:

On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote
in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple
resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel
MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open collector
transistor - assuming that's accurate the only constraint is its
collector
breakdown voltage.


I don't understand why you don't just stick an appropriately rated OC
transistor on OUT and be done with it.

That would add an inversion, but I'm unsure if it would matter in the
OP's application.


If I took some of the advice I'm getting here it wouldn't make any
difference if I hung a bloody KT88 on the end!

"flipper" wrote in message
...
On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote
in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open collector
transistor - assuming that's accurate the only constraint is its collector
breakdown voltage.


I don't understand why you don't just stick an appropriately rated OC
transistor on OUT and be done with it.

Why don't I just add a PIC or an AVR and a LCD module and forget all about
what I wanted it to do in the first place?!

On Sun, 27 Mar 2011 20:02:19 +0100, "Ian Field"
wrote:


"flipper" wrote in message
.. .
On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote
in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail so
the
source/sink output won't go high enough to cut off the P-channel MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open collector
transistor - assuming that's accurate the only constraint is its collector
breakdown voltage.


I don't understand why you don't just stick an appropriately rated OC
transistor on OUT and be done with it.

Why don't I just add a PIC or an AVR and a LCD module and forget all about
what I wanted it to do in the first place?!


Why don't you ?:-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Remember: Once you go over the hill, you pick up speed

"Jim Thompson" wrote in
message ...
On Sun, 27 Mar 2011 20:02:19 +0100, "Ian Field"
wrote:


"flipper" wrote in message
. ..
On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote
in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple
resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail
so
the
source/sink output won't go high enough to cut off the P-channel
MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open
collector
transistor - assuming that's accurate the only constraint is its
collector
breakdown voltage.


I don't understand why you don't just stick an appropriately rated OC
transistor on OUT and be done with it.

Why don't I just add a PIC or an AVR and a LCD module and forget all about
what I wanted it to do in the first place?!


Why don't you ?:-)


Why am I not surprised you said that!

"flipper" wrote in message
...
On Sun, 27 Mar 2011 20:02:19 +0100, "Ian Field"
wrote:


"flipper" wrote in message
. ..
On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote
in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple
resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail
so
the
source/sink output won't go high enough to cut off the P-channel
MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open
collector
transistor - assuming that's accurate the only constraint is its
collector
breakdown voltage.


I don't understand why you don't just stick an appropriately rated OC
transistor on OUT and be done with it.

Why don't I just add a PIC or an AVR and a LCD module and forget all about
what I wanted it to do in the first place?!


Fine with me and, by now, probably everyone else too.


A bunch of people who answered every question *EXCEPT* the one I asked is no
great loss.

On Mon, 28 Mar 2011 14:32:03 +0100, "Ian Field"
wrote:


"flipper" wrote in message
.. .
On Sun, 27 Mar 2011 20:02:19 +0100, "Ian Field"
wrote:


"flipper" wrote in message
...
On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote
in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair MOSFET
O/P
buffer, it will run from any wall wart over 12V that could potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple
resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail
so
the
source/sink output won't go high enough to cut off the P-channel
MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open
collector
transistor - assuming that's accurate the only constraint is its
collector
breakdown voltage.


I don't understand why you don't just stick an appropriately rated OC
transistor on OUT and be done with it.

Why don't I just add a PIC or an AVR and a LCD module and forget all about
what I wanted it to do in the first place?!


Fine with me and, by now, probably everyone else too.


A bunch of people who answered every question *EXCEPT* the one I asked is no
great loss.

---
Speaking of loss, I responded to your question by designing what you
said you wanted, setting it up to run on LTspice, and posting the
netlist a couple of times; Sunday being the last time.

From your lack of response I assume you've wasted my time and haven't
even bothered to run the sim, let alone look at the circuit.

I have since designed a bipolar output stage and attached it, as well
as the MOSFET version, to this post so all you should have to do is
click on the attachment(s) to view and run it.

Both circuits have shoot-through current issues, but that's left as an
exercise for the student to work through.

--
JF

"flipper" wrote in message
...
On Mon, 28 Mar 2011 14:32:03 +0100, "Ian Field"
wrote:


"flipper" wrote in message
. ..
On Sun, 27 Mar 2011 20:02:19 +0100, "Ian Field"
wrote:


"flipper" wrote in message
m...
On Sun, 27 Mar 2011 18:10:15 +0100, "Ian Field"
wrote:


"Jim Thompson"
wrote
in
message ...
On Sat, 26 Mar 2011 13:19:02 -0000, "Ian Field"
wrote:

Does anyone have any application examples of the 555 with the
source/sink
O/P used to drive the timing resistor and the discharge transistor
driving
the external load?

The project is a 555 pulse generator with a complementary pair
MOSFET
O/P
buffer, it will run from any wall wart over 12V that could
potentially
exceed the 555 ABS-MAX Vcc, so the 555 will have a simple
resistor/zener
regulator, the Vdd for the MOSFETs will be the full unregulated rail
so
the
source/sink output won't go high enough to cut off the P-channel
MOSFET.

Thanks.


I'm not seeing ANY data sheet which would indicate a higher voltage
tolerance for the discharge path that the max VCC rating.


The internal circuit shows it as a simple straight forward open
collector
transistor - assuming that's accurate the only constraint is its
collector
breakdown voltage.


I don't understand why you don't just stick an appropriately rated OC
transistor on OUT and be done with it.

Why don't I just add a PIC or an AVR and a LCD module and forget all
about
what I wanted it to do in the first place?!


Fine with me and, by now, probably everyone else too.


A bunch of people who answered every question *EXCEPT* the one I asked is
no
great loss.


People were trying to help, Jackass, and the reason you got 'different
answers' is because it became abundantly clear you asked the wrong
question.

By now, though, if you were asking where the nearest wall socket to
stick your finger in was no one would bother to warn you off.


I could show you how to disable the interlock on a microwave so you can
stick your head in it and switch it on.