LMV932-N: LMV932MAX

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

・The board output voltage was not the desired value.

Taylor：

Hi,

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

,

Vivian Gao：

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? 

,

minako yamaguchi：

,

Vivian Gao：

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?

,

minako yamaguchi：

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.

,

Vivian Gao：

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

,

minako yamaguchi：

Pin7 is at the same voltage as IN-.

Also, pin7 does not appear to be oscillating.

,

Vivian Gao：

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. 

,

minako yamaguchi：

・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?

,

Vivian Gao：

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.