BQ76952: PCHG FET drive

chong.shen

Part Number: BQ76952
Other Parts Discussed in Thread: BQ40Z50

Hi,

I have a question about the PCHG FET drive of BQ76952.From the picture below,when VPACK is 8V，the V(PCHG_ON) is typ 8.4V when PCHG mos on.This means the voltage of PCHG should be below 0V？

over 1 year ago

0 Max Verboncoeur over 1 year ago

TI__Mastermind 25980 points

Hi Chong,

The voltage likely won't go negative. I expect what happens in the scenario you've given is that the gate-source voltage decreases towards the minimum spec, keeping the voltage at or above 0V.

Regards,

Max Verboncoeur

0 chong.shen over 1 year ago in reply to Max Verboncoeur

Prodigy 70 points

Hi Max Verboncoeur,

Thank you for your reply.However, compared to BQ40z50 which show the spec details and pre-charge drive circuit below, I still want to know why increasing the V(PCHG_ON) of BQ76952? Maybe typ 7V of V(PCHG_ON) is enough to use.

Besides, the pre-charge drive circuit of BQ76952 is the same as BQ40z50? Is there a zener between VCC pin and PCHG pin inside the chip?

And how does the pre-charge drive circuit of BQ76952 works?

Looking forward to your answer!

Regards,

Chong

0 Max Verboncoeur over 1 year ago in reply to chong.shen

TI__Mastermind 25980 points

Hi Chong,

I expect that PCHG on the BQ76952 works similarly to the BQ40z50. See below from the Pin Equivalent Diagrams application note (the document currently uses the wrong figure for PCHG, but I've corrected it below).

Regards,

Max Verboncoeur

0 chong.shen over 1 year ago in reply to Max Verboncoeur

Prodigy 70 points

Hi Max Verboncoeur,

What does Current sink capability I(pulldown) shown in BQ76952 spec below means? From PCHG pin Equivalent Diagram above, there is no current source which pull down PCHG voltage to VSS. Can you comment on it?

Thanks!

Regards,

Chong

0 Max Verboncoeur over 1 year ago in reply to chong.shen

TI__Mastermind 25980 points

Hi Chong,

I recommend looking at this FAQ that explains these specs in more detail: [FAQ] BQ76952: What is the default output of PDSG/PCHG when pre-discharge and pre-charge is enabled - Power management forum - Power management - TI E2E support forums.

Regards,

Max Verboncoeur