UCC27524 - Outputs Driven with low enable pin

Mike H Meyer

Other Parts Discussed in Thread: UCC27524

I'm helping debug an issue with a UCC27524. The enable pins are attached to an RC from Vdd. For the parts being tested, at 1.4V the outputs start turning on linearly until they reach 1.9V when they fully turn on. The minimum specified turn-on in the datasheet is 1.9V. Is there something that would cause this? The enable pin has hysteresis so I wouldn't imagine that it's a ramp-up timing concern.

over 12 years ago

0 Dave Weinzierl over 12 years ago

TI__Expert 6380 points

can you post a scope shot of Vdd,enable and output as well as snip of the schematic? that sounds odd in that there is UVLO on this chip as well

0 Mike H Meyer over 12 years ago in reply to Dave Weinzierl

Expert 1560 points

For the sake of the community I've attached the scope shot as well as a portion of the schematic. Dave, I'll send the full page offline.

Enable pin (CH1), 5V logic rail (CH2), derived off of +15V which is VDD and at this point was up and stable for > 500ms), the output of the chip (out A to out B)(CH3), and the gate to source of the fet (CH4).

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UCC27524 - Outputs Driven with low enable pin