TPS40170: Turn-on start timing of High side FET at pre-bias condition

K. Sasaki14

Guru 10200 points

Part Number: TPS40170

I would like to know the timing that high side FET becomes ON at pre-bias condition.

Does high side FET start switching when device becomes enable regardless of the pre-bias voltage level?

Or does the timing of high side FET start switching change depend on pre-bias voltage level?

If the later is yes, how does the device decide start timing?

Best Regards,
Kohei Sasaki

over 5 years ago

0 Arief Hernadi over 5 years ago

TI__Mastermind 23815 points

Hi,

We will get back to you

Thanks
-Arief

0 Timothy Hegarty over 5 years ago

TI__Mastermind 49597 points

Sasaki-san,

Please review section 7.3.9 of the TPS40170 datasheet for more detail related to timing during a pre-bias startup.

Regards,

Tim

0 K. Sasaki14 over 5 years ago in reply to Timothy Hegarty

Guru 10200 points

Tim-san,

Thank you for your answer.
I have checked datasheet section 7.3.9. So I would like to know the first turn-on timing of high side FET.
I have understood low side FET turns on by SS_EAMP voltage reaches to FB voltage.

When is the high side FET first turn-on timing?
Is it just after device enable?

Best Regards,
Kohei Sasaki

0 K. Sasaki14 over 5 years ago in reply to K. Sasaki14

Guru 10200 points

Hi Team,

Sorry for pushing you.

Could anyone answer for my post?

Best Regards,
Kohei Sasaki

0 Timothy Hegarty over 5 years ago in reply to K. Sasaki14

TI__Mastermind 49597 points

Sasaki-san,

My understanding is that the first high-side pulse is initiated when the soft-start voltage exceeds the FB voltage corresponding to the output voltage pre-bias level.

Then the controller slowly initiates low-side gate drive pulses, gradually increasing the pulsewidth on a cycle-by-cycle basis over a 20-40us duration such that minimum disturbance to the output voltage occurs.

Regards,

Tim

Power management

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TPS40170: Turn-on start timing of High side FET at pre-bias condition