LMV358: Problem with burning lmv358.

Kfir Maymon

Part Number: LMV358
Other Parts Discussed in Thread: TLV9002

Hi.

I'm using a lmv358 as a voltage comparator in my product and I am suffering from burning lmv358 parts,

I try to replace them with tlv9002 but I have the same problem.

I have attached a circuit that shows the schematic.

The current source is a BQ25060DQCT charger, and the LED shows if the charge current drop from a certain point.

the sides are LED (Red, Green), and the input voltage is a 5v USB phone charger.

I know that is a better way to do it but sorry it's not my design.

0 Clemens Ladisch over 2 years ago

Guru 316440 points

Please show the power supply connections.

0 Kfir Maymon over 2 years ago

0 Clemens Ladisch over 2 years ago in reply to Kfir Maymon

Guru 316440 points

The chosen switching threshold is outside the valid input common-mode range of the LMV358. But this would not damage the device.

There is no hysteresis; it's possible that the opamp is oscillating. You need to add positive feedback.

(And the optocoupler is useless; you can replace it with another 2N7002.)

0 Kfir Maymon over 2 years ago in reply to Clemens Ladisch

thank you for your fast responses,

do you think that the oscillations are damaging the IC?

0 Clemens Ladisch over 2 years ago in reply to Kfir Maymon

Guru 316440 points

Yes.

+1 Jacob Nogaj over 2 years ago in reply to Clemens Ladisch

Hello,

I agree with the conclusion Clemens made. Inspect the output of the amplifier and the input terminals with a scope.

If we see oscillations, we will know the issue is due to lack of stability/lack of hysteresis.

Please let us know if you have any questions.

Best,

Jacob

+1 Kfir Maymon over 2 years ago in reply to Jacob Nogaj

I see oscillations on the last few percentages of charge, I will add the hysteresis to the next design.

thank you for all the good help and explanations.

best regard

Kfir Maymon.

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