On Sun, 05 Jun 2011 13:23:01 -0500, John Fields
wrote:

On Fri, 3 Jun 2011 08:17:31 -0700 (PDT), john1987
wrote:

Hi,

The input voltage is 5 volts and can go up to 60 volts but it might
get more than that too. I do not know how much but so far the maximum
limit is 60 volts. The load at the output of the DC to DC converter
needs 3.3 volts and 100mA. The DC to DC converter can be configured to
do that.

I need some circuit zener or something that can protect the DC to DC
converter if the voltage exceeds more than 40 volts or to be safe 38
volts. The minimum input to the DC to DC converter to produce 3.3
volts is 4.2 according to data sheet. But I have seen that if the
voltage is 3.7 volts than the output gets very close to 3.3 volts and
my circuit works. The protection circuitry should not let the input
voltage go higher than 38 or 40 volts and DC to DC converter should be
working all times.


Thanks

John

---
He

Version 4
SHEET 1 1268 804
WIRE -688 -256 -784 -256
WIRE -560 -256 -688 -256
WIRE -432 -256 -560 -256
WIRE 16 -256 -432 -256
WIRE 112 -256 16 -256
WIRE 160 -256 112 -256
WIRE 304 -256 256 -256
WIRE 464 -256 304 -256
WIRE 16 -240 16 -256
WIRE 400 -240 320 -240
WIRE -688 -224 -688 -256
WIRE -560 -224 -560 -256
WIRE -432 -224 -432 -256
WIRE 304 -224 304 -256
WIRE 400 -208 400 -240
WIRE 112 -192 112 -256
WIRE 16 -144 16 -176
WIRE 16 -48 16 -80
WIRE 112 -48 112 -112
WIRE 112 -48 16 -48
WIRE 176 -48 176 -208
WIRE 176 -48 112 -48
WIRE 400 0 400 -16
WIRE 400 0 320 0
WIRE 304 48 304 -144
WIRE 304 48 -368 48
WIRE -688 80 -688 -144
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WIRE 400 112 400 0
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WIRE -32 160 -272 160
WIRE 112 160 48 160
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WIRE -336 176 -560 176
WIRE 400 304 400 192
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WIRE 176 400 176 208
WIRE 176 400 48 400
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WIRE -784 720 -784 672
FLAG -784 720 0
FLAG 464 -256 Vout
SYMBOL voltage -784 528 R0
WINDOW 3 24 104 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value PULSE(0 60 0 .005)
SYMATTR InstName V1
SYMBOL pmos 256 -208 M270
SYMATTR InstName M1
SYMATTR Value FQB11P06
SYMBOL res -576 -240 R0
SYMATTR InstName R3
SYMATTR Value 5k1
SYMBOL References\\LT1009 -560 576 R0
SYMATTR InstName U2
SYMBOL res 288 -240 R0
WINDOW 0 -52 47 Left 0
WINDOW 3 -64 72 Left 0
SYMATTR InstName R4
SYMATTR Value 30.1k
SYMBOL res 288 496 R0
WINDOW 0 -56 37 Left 0
WINDOW 3 -64 71 Left 0
SYMATTR InstName R5
SYMATTR Value 2320
SYMBOL zener -672 608 R180
WINDOW 0 -39 31 Left 0
WINDOW 3 -81 3 Left 0
SYMATTR InstName D1
SYMATTR Value DFLZ33
SYMBOL npn 112 112 R0
SYMATTR InstName Q1
SYMATTR Value BC546B
SYMBOL res 96 -208 R0
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WINDOW 3 -42 73 Left 0
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SYMATTR Value 10k
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SYMATTR Value 1000
SYMBOL Opamps\\LT1007 -304 96 R0
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SYMBOL res 160 496 R0
WINDOW 0 -40 47 Left 0
WINDOW 3 -51 78 Left 0
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SYMATTR Value 1000
SYMBOL npn -16 432 R0
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SYMATTR Value 2N3904
SYMBOL res -448 -240 R0
SYMATTR InstName R9
SYMATTR Value 100k
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SYMATTR InstName R10
SYMATTR Value 100k
SYMBOL Comparators\\LT1716 -208 480 R0
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SYMATTR InstName R8
SYMATTR Value 10k
SYMBOL res 64 144 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R11
SYMATTR Value 10k
SYMBOL zener 32 -176 R180
WINDOW 0 46 33 Left 0
WINDOW 3 22 -3 Left 0
SYMATTR InstName D2
SYMATTR Value BZX84C12L
SYMBOL zener 32 -80 R180
WINDOW 0 46 31 Left 0
WINDOW 3 26 -10 Left 0
SYMATTR InstName D3
SYMATTR Value BZX84C12L
TEXT -768 696 Left 0 !.tran 0 .01 0 1e-6 startup uic
TEXT 352 480 Left 0 ;STARTUP
TEXT 336 152 Left 0 ;36V SERVO
TEXT 328 -176 Left 0 ;SERIES PASS
TEXT 336 -144 Left 0 ;REGLATOR
TEXT 368 -112 Left 0 ;AND
TEXT 328 -80 Left 0 ;GATE-SOURCE
TEXT 360 -48 Left 0 ;CLAMP

Too complex, see attachment...

...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 |

I love to cook with wine. Sometimes I even put it in the food.

On Sun, 05 Jun 2011 12:20:34 -0700, Jim Thompson
wrote:


Too complex, see attachment...

...Jim Thompson

---
Something's wrong.

With a 5V supply, how can you expect to get 5V out of an emitter
follower?

--
JF

On Sun, 05 Jun 2011 15:09:06 -0500, John Fields
wrote:

On Sun, 05 Jun 2011 12:20:34 -0700, Jim Thompson
wrote:


Too complex, see attachment...

...Jim Thompson

---
Something's wrong.

With a 5V supply, how can you expect to get 5V out of an emitter
follower?

The OP said his device was guaranteed at 4.2V and seemed pretty good
down to 3.7V ;-)

...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 |

I love to cook with wine. Sometimes I even put it in the food.

On Sun, 05 Jun 2011 13:12:04 -0700, Jim Thompson
wrote:

On Sun, 05 Jun 2011 15:09:06 -0500, John Fields
wrote:

On Sun, 05 Jun 2011 12:20:34 -0700, Jim Thompson
wrote:


Too complex, see attachment...

...Jim Thompson

---
Something's wrong.

With a 5V supply, how can you expect to get 5V out of an emitter
follower?

The OP said his device was guaranteed at 4.2V and seemed pretty good
down to 3.7V ;-)

...Jim Thompson

---
The OP doesn't know what the **** he's talking about, and is basing
his 3.7V data on non-guaranteed characteristics of a single device
he's dicking around with.

Even with that, the data for your circuit shows that with 5V out of
the bulk supply he'll get about 2.5V into the switcher, which won't
work, for sure.

With my excellent "P" channel pass device design, , 5V out of the
supply will get him 4.95V into the switcher.

More parts than yours, for sure, but mine works down to the bitter
end.

--
JF

On Sun, 05 Jun 2011 16:54:12 -0500, John Fields
wrote:

On Sun, 05 Jun 2011 13:12:04 -0700, Jim Thompson
wrote:

On Sun, 05 Jun 2011 15:09:06 -0500, John Fields
wrote:

On Sun, 05 Jun 2011 12:20:34 -0700, Jim Thompson
wrote:


Too complex, see attachment...

...Jim Thompson

---
Something's wrong.

With a 5V supply, how can you expect to get 5V out of an emitter
follower?

The OP said his device was guaranteed at 4.2V and seemed pretty good
down to 3.7V ;-)

...Jim Thompson

---
The OP doesn't know what the **** he's talking about, and is basing
his 3.7V data on non-guaranteed characteristics of a single device
he's dicking around with.

Even with that, the data for your circuit shows that with 5V out of
the bulk supply he'll get about 2.5V into the switcher, which won't
work, for sure.

With my excellent "P" channel pass device design, , 5V out of the
supply will get him 4.95V into the switcher.

More parts than yours, for sure, but mine works down to the bitter
end.

Of course. I left the fine details of mine as an exercise for the
student ;-)

...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 |

I love to cook with wine. Sometimes I even put it in the food.