UC1707: Is it susceptible to latchup when driving input when power not applied to VCC and Vin+

Jeffrey Yee

Part Number: UC1707

Working through an anomaly where we had blown driver chips. I suspect that we had the inputs being driven prior to powering on the chips. Is this chip susceptible to latchup in this condition where VCC and Vin+ would have a low impedence path to ground? Deliding the chips, we see the wirebonds were blown on the VCC and Vin+

over 6 years ago

0 Daniel Hartung over 6 years ago

TI__Mastermind 26855 points

Hey Jeffrey,

The maximum voltage rating on the part for the analog inputs is Vin.

If a voltage greater than Vin is applied to the inputs this would explain the issue you are seeing.

Thanks,

Daniel

0 Jeffrey Yee over 6 years ago in reply to Daniel Hartung

Prodigy 30 points

Let me clarify. Would a latchup condition occur if input A or input B (or the inverting A/B) was driven prior to applying Vin+ or VCC?

0 Daniel Hartung over 6 years ago in reply to Jeffrey Yee

TI__Mastermind 26855 points

Hey Jeffrey,

Applying voltage to A or B before applying Vin+ or VCC will cause an over voltage issue on those pins.

Thanks,
Daniel

0 Jeffrey Yee over 6 years ago in reply to Daniel Hartung

Prodigy 30 points

Can you give me some additional details on this? Also where on the data sheet is this shown?

Thanks,
Jeff

0 Daniel Hartung over 6 years ago in reply to Jeffrey Yee

TI__Mastermind 26855 points

Hey Jeff,

This is shown under "Absolute Maximum Ratings" for "Analog Stop Inputs" which are N.I and INV pins.

Violating our ABSOLUTE MAXIMUM RATINGS can cause the part to be damaged.

Thanks,

Daniel

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UC1707: Is it susceptible to latchup when driving input when power not applied to VCC and Vin+