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INA213 failure

Milan Laketic
Prodigy 70 points

Other Parts Discussed in Thread: INA213

Hi, I have problem with INA213 opamps. I'm using two of this precision amplifiers, one at the input and one at the output stage of the discreet buck converter running at 240kHz. Input stage opamp is connected directly to the high side mosfet, while output stage is connected after inductor, with schottky diode between them. Input amp is measuring current from photovoltiac array (14V open circuit), output amp is measuring current from buck converter. Problem is with input stage INA213 that keeps failing.

Moment of failure is followed with cracking sound, probably from opamp it self (although I can't see any physical crack) , and it happens during programming of the MCU controlling buck converter. When checked with multimeter, I found out that one of the opamp inputs is now connected directly to the ground (only 5 ohms between GND and one of the inputs).

I've used reference design right from the first page of INA213 data sheet. Am I missing something about circuit design?

One thing that I'm considering is that opamp got voltage spike from buck converter during programming sequence when unknown state could have ocurred, since it is directly connected to the high side P channel mosfet. Could this be possible source of the problem and how should it be rectified?

 

  • 0
    TI__Genius 12375 points

    Milan,

    By measuring directly across the high-side FET of your buck converter, you are exposing the INA213 to transient voltages that are most likely triggering the on-chip ESD structures and damaging the part. Once triggered, these structures can latch, which is why you are seeing a low impedance pathway from the input pins to ground. Generally, the input filtering shown in the datasheet Figure 24 (Cfilter ~10nF) will slow the edge rate of transient signals enough to protect the part. Additional external ESD protection can be added as is shown in Figure 27 and 28.