why OPA1632D got so hot?

Hongmei Wan

Other Parts Discussed in Thread: LME49724, OPA1632, TSV911, TLV7011, AMC1311, THP210, TINA-TI

Hello,

The following is my OPA1632D schematic. Input is a signal from voltage sensor or current sensor. Currently NO input signals yet go in and the differential output is only followed by a comparator.

The temperature is 63.9C at 22C ambient. It seems it can't work for a real-life circuit under this high temperature.

First I use LME49724 with thermal PAD but I made a mistake to tie the thermal pad to ground, then I found this replacement without thermal pad.

I don't understand why? What makes the temperature so high? What is your suggestions to help my circuit work?

Before I use differential OPA, I use a non-differential OPA and the temperature is 37.2C at 22C ambient. Does differential OPA get hotter than non-differential OPA under same conditions?

By the way, why the part number not recognized in the above required field?

Thanks for help in advance,

Hongmei Wan

over 2 years ago

0 kai klaas69 over 2 years ago

Guru 140200 points

Hi Hongmei,

not sure whta the purpose of your circuit is? double wave rectifier?

In any case, when the junction capacitance of D401 and D402 is too high, the OPA1632 becomes instable:

hongmei_opa1632.TSC

Why are your feedback resistors so high? Haven't you read section 8.1.1.1 of datasheet of OPA1632?

So, decrease the feedback resistances:

And add isolation resistors at the outputs:

Kai

0 Hongmei Wan over 2 years ago in reply to kai klaas69

Intellectual 610 points

Thanks a lot Kai!!!

OMG, it is my setting problem. I read it but there is no max. resistance recommended and I try to get a smaller current.

1. So I have to reduce the resistors not to exceed what the datasheet shows, RF (4020)?

2. I found another replacement, THP210DR. This one doesn't have the resistor matching issue, can I use my original values, RF=25.5k, RG=2k-7.15k. I have 14 of these circuit on one board and 12 boards are populated. It would be extremely great not to change it, too much work. But if you say I have to change it, then I will still be happy to do so to make my circuit work.

The inputs are a voltage sensor (AMC1311) or current sensor outputs; The outputs are going to differential to single OPA (TSV911) then to ADC of the DSP (28379D) which is located on other board, and also going to the TLV7011 for over voltage/over current protection which is on the same board. Following is the whole setting which might be hard to see clearly.

Thanks again,

Hongmei

0 kai klaas69 over 2 years ago in reply to Hongmei Wan

Guru 140200 points

Hi Hongmei,

TI says "access denied" when I want to fetch the TINA-TI model from the product's website to run a simulation. So please run this simulation by yourself. Just open my simulation file and replace the OPA1632 by the THP210.

Kai