LMV932-N: LMV932MAX

minako yamaguchi

Part Number: LMV932-N

The following problems occurred with the ”LMA932MAX” I purchased previously.

・The board output voltage was not the desired value.

・The amplifier output was normal, but the voltage value became abnormal when it was passed through the final stage buffer.

　The voltage before and after the buffer should be approximately the same.

・When measuring the input terminal of the buffer, the operation when the op amp is in negative feedback is.

The virtual short is not established.

Please provide an analysis and answer regarding these problems.

4 个月前

0 Taylor 4 个月前

TI__Mastermind 37325 points

Hi,

We have received your post and the investigation will take some time. Thank you for your patience.

0 Vivian Gao 4 个月前回复 Taylor

TI__Mastermind 38790 points

Hello Jiahui,

you said：

passed through the final stage buffer.

Is LMV932 used for this function?

you said：

The board output voltage was not the desired value.

What was the output voltage. Does board output go a connector?

0 minako yamaguchi 3 个月前回复 Vivian Gao

Prodigy 10 points

0 Vivian Gao 3 个月前回复 minako yamaguchi

TI__Mastermind 38790 points

The LMV932 is one of the following.

1) Damaged

2) Improperly connected, does not match schematic.

3) Output lover loaded.

What was the output voltage. Does board output go a connector?

The questions above are worth repeating.

Also, does this happen of just one or a few sample or all of them?

0 minako yamaguchi 3 个月前回复 Vivian Gao

Prodigy 10 points

The signal voltage from the previous circuit at the input terminal is
approximately 300mV, while the voltage at the output terminal is approximately
40mV higher.
The board output is connected to a connector.
The number of defects is 4p for N=300p.
I would like to know what could be the cause of this phenomenon.

0 Vivian Gao 3 个月前回复 minako yamaguchi

TI__Mastermind 38790 points

So IN+ is 300mV and IN- is 340mV; but what is pin 7 DC voltage? Is pin 7 oscillating?

0 minako yamaguchi 3 个月前回复 Vivian Gao

Prodigy 10 points

Pin7 is at the same voltage as IN-.

Also, pin7 does not appear to be oscillating.

0 Vivian Gao 3 个月前回复 minako yamaguchi

TI__Mastermind 38790 points

If pin 7 voltage is same as IN- voltage then output current is low. How much capacitance is on output?

you said：

does this happen of just one or a few sample or all of them?

Is this a old or new design? Did it work with in the past?

you said：

pin7 does not appear to be oscillating.

If all/most samples fail then it is oscillating.

0 minako yamaguchi 3 个月前回复 Vivian Gao

Prodigy 10 points

・The low output current may mean that there is slight oscillation, but I have
not been able to confirm this.

・As I have answered before, this issue is occurring in 4 out of 300 units.
This circuit board has been in production for about 10 years, and several
thousand units have already been shipped,
but this problem has never occurred before, so it is not thought to be a problem
with the circuit.
Also, the components used have not been changed during this time.

・Furthermore, if the LMV932 on the defective board is replaced with an unused
LMV932,
it works normally,
so it is clearly damage to the op amp on the defective board.
Why did it only occur in a few units this time? Is it possible that the op amp
lot is faulty?

0 Vivian Gao 3 个月前回复 minako yamaguchi

TI__Mastermind 38790 points

The most common causes for ESD/EOS damage occurs when high voltage arcs over isolation or from connection / disconnection of a connector. In this case, more likely that stress entering board on the connector.

I assume these failures occur during production. So check at the fail test point backwards to find the source of the overstress.

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LMV932-N: LMV932MAX