Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
Hello:- I'm just wrapping up a design that includes a DCP-02 12V:5V isolated unregulated 600kHz DC-DC converter. Everything seems straightforward, the unit is supposed to include thermal shutdown at 150°C chip temperature which should typically protect the converter if the output is inadvertently overloaded. This project will see wide Ta range. However, I've just run across a tray of bad DCP-02 units of unknown origin- containing about 50 duff units, and also I recently came across a hobbyist who had problems with his dying recently. This can be explained away by assuming that those people were not obeying the rather strict abs. max. input voltage rating (15V for the 12V units, for example), but I'd sure like to know any info to the contrary. Thanks! Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
#2
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
On Tue, 06 Apr 2004 15:37:27 GMT, Spehro Pefhany
wrote: Hello:- I'm just wrapping up a design that includes a DCP-02 12V:5V isolated unregulated 600kHz DC-DC converter. Everything seems straightforward, the unit is supposed to include thermal shutdown at 150°C chip temperature which should typically protect the converter if the output is inadvertently overloaded. This project will see wide Ta range. However, I've just run across a tray of bad DCP-02 units of unknown origin- containing about 50 duff units, and also I recently came across a hobbyist who had problems with his dying recently. This can be explained away by assuming that those people were not obeying the rather strict abs. max. input voltage rating (15V for the 12V units, for example), but I'd sure like to know any info to the contrary. Thanks! Best regards, Spehro Pefhany We don't use the specific DCP021205 that you are asking about, but we have used a few thousand DCP02 converters (different voltages) over the past few years. These are used in rail car applications, with ambient temperatures in the enclosure getting close to +85C. We are required to not exceed 50% of the load rating on any power supply or DC-DC converter, so we don't push them as hard as many people would. That having been said, we have been very happy with their reliability. As far as I know, we have not had any fail yet in the field, and I haven't heard about any fallout in production test and burn in. ================================ Greg Neff VP Engineering *Microsym* Computers Inc. |
#3
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
On Tue, 06 Apr 2004 15:37:27 GMT, Spehro Pefhany
wrote: Hello:- I'm just wrapping up a design that includes a DCP-02 12V:5V isolated unregulated 600kHz DC-DC converter. Everything seems straightforward, the unit is supposed to include thermal shutdown at 150°C chip temperature which should typically protect the converter if the output is inadvertently overloaded. This project will see wide Ta range. However, I've just run across a tray of bad DCP-02 units of unknown origin- containing about 50 duff units, and also I recently came across a hobbyist who had problems with his dying recently. This can be explained away by assuming that those people were not obeying the rather strict abs. max. input voltage rating (15V for the 12V units, for example), but I'd sure like to know any info to the contrary. Thanks! Best regards, Spehro Pefhany We don't use the specific DCP021205 that you are asking about, but we have used a few thousand DCP02 converters (different voltages) over the past few years. These are used in rail car applications, with ambient temperatures in the enclosure getting close to +85C. We are required to not exceed 50% of the load rating on any power supply or DC-DC converter, so we don't push them as hard as many people would. That having been said, we have been very happy with their reliability. As far as I know, we have not had any fail yet in the field, and I haven't heard about any fallout in production test and burn in. ================================ Greg Neff VP Engineering *Microsym* Computers Inc. |
#4
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
On Tue, 06 Apr 2004 12:50:50 -0400, the renowned Greg Neff
wrote: On Tue, 06 Apr 2004 15:37:27 GMT, Spehro Pefhany wrote: Hello:- I'm just wrapping up a design that includes a DCP-02 12V:5V isolated unregulated 600kHz DC-DC converter. Everything seems straightforward, the unit is supposed to include thermal shutdown at 150°C chip temperature which should typically protect the converter if the output is inadvertently overloaded. This project will see wide Ta range. However, I've just run across a tray of bad DCP-02 units of unknown origin- containing about 50 duff units, and also I recently came across a hobbyist who had problems with his dying recently. This can be explained away by assuming that those people were not obeying the rather strict abs. max. input voltage rating (15V for the 12V units, for example), but I'd sure like to know any info to the contrary. Thanks! Best regards, Spehro Pefhany We don't use the specific DCP021205 that you are asking about, but we have used a few thousand DCP02 converters (different voltages) over the past few years. These are used in rail car applications, with ambient temperatures in the enclosure getting close to +85C. We are required to not exceed 50% of the load rating on any power supply or DC-DC converter, so we don't push them as hard as many people would. That having been said, we have been very happy with their reliability. As far as I know, we have not had any fail yet in the field, and I haven't heard about any fallout in production test and burn in. Thanks a lot, Greg, that's what I needed to hear- from the right kind of source. We won't be pushing them either, power-wise, but the Ta may approach 85°C. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
#5
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
On Tue, 06 Apr 2004 12:50:50 -0400, the renowned Greg Neff
wrote: On Tue, 06 Apr 2004 15:37:27 GMT, Spehro Pefhany wrote: Hello:- I'm just wrapping up a design that includes a DCP-02 12V:5V isolated unregulated 600kHz DC-DC converter. Everything seems straightforward, the unit is supposed to include thermal shutdown at 150°C chip temperature which should typically protect the converter if the output is inadvertently overloaded. This project will see wide Ta range. However, I've just run across a tray of bad DCP-02 units of unknown origin- containing about 50 duff units, and also I recently came across a hobbyist who had problems with his dying recently. This can be explained away by assuming that those people were not obeying the rather strict abs. max. input voltage rating (15V for the 12V units, for example), but I'd sure like to know any info to the contrary. Thanks! Best regards, Spehro Pefhany We don't use the specific DCP021205 that you are asking about, but we have used a few thousand DCP02 converters (different voltages) over the past few years. These are used in rail car applications, with ambient temperatures in the enclosure getting close to +85C. We are required to not exceed 50% of the load rating on any power supply or DC-DC converter, so we don't push them as hard as many people would. That having been said, we have been very happy with their reliability. As far as I know, we have not had any fail yet in the field, and I haven't heard about any fallout in production test and burn in. Thanks a lot, Greg, that's what I needed to hear- from the right kind of source. We won't be pushing them either, power-wise, but the Ta may approach 85°C. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
#6
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
Spehro Pefhany wrote:
On Tue, 06 Apr 2004 12:50:50 -0400, the renowned Greg Neff wrote: On Tue, 06 Apr 2004 15:37:27 GMT, Spehro Pefhany wrote: Hello:- I'm just wrapping up a design that includes a DCP-02 12V:5V isolated unregulated 600kHz DC-DC converter. Everything seems straightforward, the unit is supposed to include thermal shutdown at 150°C chip temperature which should typically protect the converter if the output is inadvertently overloaded. This project will see wide Ta range. However, I've just run across a tray of bad DCP-02 units of unknown origin- containing about 50 duff units, and also I recently came across a hobbyist who had problems with his dying recently. This can be explained away by assuming that those people were not obeying the rather strict abs. max. input voltage rating (15V for the 12V units, for example), but I'd sure like to know any info to the contrary. Thanks! Best regards, Spehro Pefhany We don't use the specific DCP021205 that you are asking about, but we have used a few thousand DCP02 converters (different voltages) over the past few years. These are used in rail car applications, with ambient temperatures in the enclosure getting close to +85C. We are required to not exceed 50% of the load rating on any power supply or DC-DC converter, so we don't push them as hard as many people would. That having been said, we have been very happy with their reliability. As far as I know, we have not had any fail yet in the field, and I haven't heard about any fallout in production test and burn in. Thanks a lot, Greg, that's what I needed to hear- from the right kind of source. We won't be pushing them either, power-wise, but the Ta may approach 85°C. Another issue you may want to look at is the size of any output capacitor that you put on the unit. I know that I didn't read the data sheet carefully with some Power Conversions units and burned up a couple samples before I caught the problem. Too large of an output capacitor will lunch the driver transistors on startup. This might have happened to your tray of parts. |
#7
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
Spehro Pefhany wrote:
On Tue, 06 Apr 2004 12:50:50 -0400, the renowned Greg Neff wrote: On Tue, 06 Apr 2004 15:37:27 GMT, Spehro Pefhany wrote: Hello:- I'm just wrapping up a design that includes a DCP-02 12V:5V isolated unregulated 600kHz DC-DC converter. Everything seems straightforward, the unit is supposed to include thermal shutdown at 150°C chip temperature which should typically protect the converter if the output is inadvertently overloaded. This project will see wide Ta range. However, I've just run across a tray of bad DCP-02 units of unknown origin- containing about 50 duff units, and also I recently came across a hobbyist who had problems with his dying recently. This can be explained away by assuming that those people were not obeying the rather strict abs. max. input voltage rating (15V for the 12V units, for example), but I'd sure like to know any info to the contrary. Thanks! Best regards, Spehro Pefhany We don't use the specific DCP021205 that you are asking about, but we have used a few thousand DCP02 converters (different voltages) over the past few years. These are used in rail car applications, with ambient temperatures in the enclosure getting close to +85C. We are required to not exceed 50% of the load rating on any power supply or DC-DC converter, so we don't push them as hard as many people would. That having been said, we have been very happy with their reliability. As far as I know, we have not had any fail yet in the field, and I haven't heard about any fallout in production test and burn in. Thanks a lot, Greg, that's what I needed to hear- from the right kind of source. We won't be pushing them either, power-wise, but the Ta may approach 85°C. Another issue you may want to look at is the size of any output capacitor that you put on the unit. I know that I didn't read the data sheet carefully with some Power Conversions units and burned up a couple samples before I caught the problem. Too large of an output capacitor will lunch the driver transistors on startup. This might have happened to your tray of parts. |
#8
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
On Tue, 06 Apr 2004 10:40:11 -0700, Jim Stewart
wrote: (snip) Another issue you may want to look at is the size of any output capacitor that you put on the unit. I know that I didn't read the data sheet carefully with some Power Conversions units and burned up a couple samples before I caught the problem. Too large of an output capacitor will lunch the driver transistors on startup. This might have happened to your tray of parts. We have been using ceramic capacitors (a few uF) on the output. I would also recommend reading the application notes listed on the DCP02 product page: http://focus.ti.com/docs/prod/folder...dcp021205.html These things can generate a lot of RFI, so you have to watch this. The transformer has some healthy ringing at around 55MHz. Using ferrite bead and ceramic cap filters on the outputs is strongly recommended. If you have more than one DCP02 in a box then make sure that they are synchronized (best to use polyphase) to avoid beat frequencies, and to avoid simultaneous current peaks on the input supply. ================================ Greg Neff VP Engineering *Microsym* Computers Inc. |
#9
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
On Tue, 06 Apr 2004 10:40:11 -0700, Jim Stewart
wrote: (snip) Another issue you may want to look at is the size of any output capacitor that you put on the unit. I know that I didn't read the data sheet carefully with some Power Conversions units and burned up a couple samples before I caught the problem. Too large of an output capacitor will lunch the driver transistors on startup. This might have happened to your tray of parts. We have been using ceramic capacitors (a few uF) on the output. I would also recommend reading the application notes listed on the DCP02 product page: http://focus.ti.com/docs/prod/folder...dcp021205.html These things can generate a lot of RFI, so you have to watch this. The transformer has some healthy ringing at around 55MHz. Using ferrite bead and ceramic cap filters on the outputs is strongly recommended. If you have more than one DCP02 in a box then make sure that they are synchronized (best to use polyphase) to avoid beat frequencies, and to avoid simultaneous current peaks on the input supply. ================================ Greg Neff VP Engineering *Microsym* Computers Inc. |
#10
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
On Tue, 06 Apr 2004 10:40:11 -0700, the renowned Jim Stewart
wrote: Another issue you may want to look at is the size of any output capacitor that you put on the unit. I know that I didn't read the data sheet carefully with some Power Conversions units and burned up a couple samples before I caught the problem. Too large of an output capacitor will lunch the driver transistors on startup. This might have happened to your tray of parts. Thanks. I'm actually under the recommended value for this. That doesn't sound like a very good design that would die from too much capacitance on the output. I'd expect them to be able to take a dead short without dying, let alone just charging up a cap. 8-( The tray of parts came from another company (now defunct) so I'll probably never know what they were up to. Date codes are all 1999. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
#11
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
On Tue, 06 Apr 2004 10:40:11 -0700, the renowned Jim Stewart
wrote: Another issue you may want to look at is the size of any output capacitor that you put on the unit. I know that I didn't read the data sheet carefully with some Power Conversions units and burned up a couple samples before I caught the problem. Too large of an output capacitor will lunch the driver transistors on startup. This might have happened to your tray of parts. Thanks. I'm actually under the recommended value for this. That doesn't sound like a very good design that would die from too much capacitance on the output. I'd expect them to be able to take a dead short without dying, let alone just charging up a cap. 8-( The tray of parts came from another company (now defunct) so I'll probably never know what they were up to. Date codes are all 1999. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
#12
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
Greg Neff wrote in message . ..
On Tue, 06 Apr 2004 10:40:11 -0700, Jim Stewart wrote: (snip) Another issue you may want to look at is the size of any output capacitor that you put on the unit. I know that I didn't read the data sheet carefully with some Power Conversions units and burned up a couple samples before I caught the problem. Too large of an output capacitor will lunch the driver transistors on startup. This might have happened to your tray of parts. We have been using ceramic capacitors (a few uF) on the output. I would also recommend reading the application notes listed on the DCP02 product page: http://focus.ti.com/docs/prod/folder...dcp021205.html These things can generate a lot of RFI, so you have to watch this. The transformer has some healthy ringing at around 55MHz. Using ferrite bead and ceramic cap filters on the outputs is strongly recommended. If you have more than one DCP02 in a box then make sure that they are synchronized (best to use polyphase) to avoid beat frequencies, and to avoid simultaneous current peaks on the input supply. ================================ Greg Neff VP Engineering *Microsym* Computers Inc. Had very similar experience with EMI and these parts. During startup, current spikes reach 2.5A, regardless of output loading (or the lack thereof). If your power supply comes up slowly, the converters will produce these spikes for the duration. Very high fields are found near the center of the modules, and parasitic capacitance from input to output is something like 30pF, IIRC. So, there's a need to bypass the common mode current. For us, the most effective approach was to put a patch of copper immediately underneath the module, unconnected to any pins. This provides a return path for the CM currents without injecting any into either ground plane. We also ended up using a high capacitance MLCC (10uF Y5V) to bypass the primary side. Lytics and Ta caps had too much ESR. Paul Mathews |
#13
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
Greg Neff wrote in message . ..
On Tue, 06 Apr 2004 10:40:11 -0700, Jim Stewart wrote: (snip) Another issue you may want to look at is the size of any output capacitor that you put on the unit. I know that I didn't read the data sheet carefully with some Power Conversions units and burned up a couple samples before I caught the problem. Too large of an output capacitor will lunch the driver transistors on startup. This might have happened to your tray of parts. We have been using ceramic capacitors (a few uF) on the output. I would also recommend reading the application notes listed on the DCP02 product page: http://focus.ti.com/docs/prod/folder...dcp021205.html These things can generate a lot of RFI, so you have to watch this. The transformer has some healthy ringing at around 55MHz. Using ferrite bead and ceramic cap filters on the outputs is strongly recommended. If you have more than one DCP02 in a box then make sure that they are synchronized (best to use polyphase) to avoid beat frequencies, and to avoid simultaneous current peaks on the input supply. ================================ Greg Neff VP Engineering *Microsym* Computers Inc. Had very similar experience with EMI and these parts. During startup, current spikes reach 2.5A, regardless of output loading (or the lack thereof). If your power supply comes up slowly, the converters will produce these spikes for the duration. Very high fields are found near the center of the modules, and parasitic capacitance from input to output is something like 30pF, IIRC. So, there's a need to bypass the common mode current. For us, the most effective approach was to put a patch of copper immediately underneath the module, unconnected to any pins. This provides a return path for the CM currents without injecting any into either ground plane. We also ended up using a high capacitance MLCC (10uF Y5V) to bypass the primary side. Lytics and Ta caps had too much ESR. Paul Mathews |
#14
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
Spehro, I believe the DCP02 only has a thermal shutdown which may not be fast
enough to protect the converter against a short. But the sync pin allows to stop the oscillator so I guess it could be tied into the usual current sense scheme if you have to protect against overload. Personally I am not a fan of such integrated DC-DC solutions, and not just because they are usually $5 and up per device. But at least these things can be synchronized. Regards, Joerg. |
#15
|
|||
|
|||
Reliability of TI/BB DCP02 DC-DC converters
Spehro, I believe the DCP02 only has a thermal shutdown which may not be fast
enough to protect the converter against a short. But the sync pin allows to stop the oscillator so I guess it could be tied into the usual current sense scheme if you have to protect against overload. Personally I am not a fan of such integrated DC-DC solutions, and not just because they are usually $5 and up per device. But at least these things can be synchronized. Regards, Joerg. |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Phase Converters vs. VFDs | Metalworking |