OPA857: failure issue when APD is soldered

Jyoti Purohit

Part Number: OPA857

This device is used in our OTDR design.

We are facing an issue with one of the Analog Front End component OPA857 which is used as the first stage of the analog receiver, i.e.Transimpedance amplifier, to convert the photocurrent from APD to an equivalent voltage, followed by a differential amplifier which feeds in to ADC input.

I have attached our schematics for reference.

The issue observed - We were using the APD on a socket .When we directly soldered the APD on the PCB, the transimpedence amplifier component ( OPA857 ) failed . We observed this issue in two boards which we are using for testing.

Can we get input from TI experts on what could be the cause for this issue ?

over 7 years ago

0 Hasan Babiker31 over 7 years ago

TI__Genius 15605 points

Hey Jyoti,

It doesnt seem like the schematic was attached to the post, do you mind providing it again? Can you further clarify what you mean when you say the TIA failed? Also does the APD board work fine when using the socket?

Best,
Hasan Babiker

0 Jyoti Purohit over 7 years ago in reply to Hasan Babiker31

Prodigy 30 points

The board was working fine when APD was on socket. Once the APD was directly soldered , we found that OPA857 has failed since the Analog voltage 3.3V dropped in the card. It got restored only when OPA857 was isolated. I have attached the schematics for your reference . Signal APD-In is connected to the IN pin of OPA857.

Regards

Jyoti

0 kai klaas69 over 7 years ago in reply to Jyoti Purohit

Guru 140200 points

Hi Jyoti,

is the polarity of the APD correct when being soldered directly into the PCB?

Kai

0 Jyoti Purohit over 7 years ago in reply to kai klaas69

Prodigy 30 points

The polarity is correct. We are using Coaxial package component D5 in the PCB. D2 is not populated .

0 kai klaas69 over 7 years ago in reply to Jyoti Purohit

Guru 140200 points

Hi Jyoti,

hhm, could have something gone wrong during the soldering? Can you check whether the OPA857 is still soldered properly? Could it be an ESD issue during the soldering? Or an overheating?

Kai

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OPA857: failure issue when APD is soldered