OPA2172: OPA2172 SCH review and the reason for burnout

benson luo

Prodigy 60 points

Part Number: OPA2172

We have a power module product that uses TI's OPA2172; in this production of 100pcs PCBA, 8pcs OPA2172 burned out;

The symptoms of a burned out IC are as follows:

1) Refer to the table for measuring the pin voltage of burned-out ICs. Most of them are burnt-out U7-2 op amps;

2) Among them, 1pcs OPA2172 power supply series resistors R28 and R29 are burnt and disconnected.

3) 2pcs board U4/U5 is also burned out

Need your support:

1) Check whether the schematic is correct or where it can be optimized; (If the sch is not clear enough, I can send you the PDF via friend)

2) What are the possible reasons for OPA2172 burning, and what analysis can we do?

Hope to receive your reply as soon as possible.

thank you for your support!

The sch diagram is as follows:

8 months ago

0 Ron Michallick 8 months ago

TI__Guru**** 154086 points

Benson,

I assume the pin voltage check is a DMM (or curve tracer) diode check (out or in circuit?). On the left side, there may not be an issue because I don't believe the red and black leads were connected consistently.

Does the -5V go positive voltage during power up or power down? Pin 5 should have some resistance to protect the input from this positive pin 4 voltage. The pin 7 short is a bit surprising ; where does this signal go? What is value for R6, R8?

It would be a good idea to check all op amp pins for over voltages during power up, down, fast VOUT changes.

0 benson luo 8 months ago

Prodigy 60 points

Hi Ron

Thank you for your prompt reply!

Q1: As you said，We measure the pin voltage of the IC through the DMM diode, and the IC is out circuit

Q2: The -5V go positive voltage during power up (the waveform as follows)；

what problems may be caused if-5V go positive voltage; Two days ago, we have tried changing -5V to +5V , the opa2172 can work normally, did't it just effect the voltage output swing?

Q3: The pin 7 goes to MCU ADC, and it used to monitor the voltage of VOUT

Q4: the value R8 is 400kΩ, R9 is 10kΩ, so the VOUT is about 88V;

Please help to check the SCH first. In addition to adding a resistor to pin5 to ground, are there any other problems or needs to be modified in SCH? If so please tell us.

Thanks again!