UCC27201DDA waveform is problem?

Bob Lee62837

Mastermind 7230 points

Dear Support member,

My customer created board at UCC27201DDA.

The schematics and waveform was attached file.

The inclusion of Delay circuit in the preceding stage,
HO terminal waveform became in such a waveform page 2, page 3.

Is this waveform, normal operation?
Is this a problem waveform?

If this waveform is abnormal operation or problem,
Could you teach countermeasure?

Best regard.
Bob Lee.

About UCC27201DDA waveform.pdf

over 10 years ago

0 Kening Gao over 10 years ago

TI__Expert 5900 points

Hi Bob,
First the input/output logic is right.
on the second page, before the red circle you drawed, voltage on HS is zero. So after Hi high level, HO will output to make HO-HS high.
On the third page, HO-HS changed to LOW before the red circle. so in the red circle, HO-HS is almost zero.
I don't see the problem.
Hope this can help you.

Br

0 Bob Lee62837 over 10 years ago in reply to Kening Gao

Mastermind 7230 points

Dear Kening Gao,

Thank you very much for reply.
I understood not problem.

May I ask a add question?

On the third page, red circle HO(pin 3) is voltage 20V waveform.

Why will be in this waveform?

If HO-HS changed to LOW before the red circle,
HO(pin 3) will not became 0V soon?

Best regard.
Bob Lee.

0 Kening Gao over 10 years ago in reply to Bob Lee62837

TI__Expert 5900 points

Hi Bob,
There is output capacitor of the MOSFET.
So in the red circle, both HO-HS and LO-GND are low, no MOSFET is turned on.
The voltage of Coss of low side MOS will keep at 20V for there is no discharging on the Coss.

Does it make sense?

Br

0 Bob Lee62837 over 10 years ago in reply to Kening Gao

Mastermind 7230 points

Dear Kening Gao,

Thank you very much for reply.

Best regard.

Bob Lee.

Power management

Power management forum

UCC27201DDA waveform is problem?