BQ24780S BATDRV drops around VBAT=7V

masahiko shimizu

Other Parts Discussed in Thread: BQ24780S

Hi,

My customer is using BQ24780S(EVM).
They have a issue of dropping BATDRV in a moment.
Please see the attached file.

This issue occurs around VBAT=7V(not connecting AC adapter).

Could you give me advise about this situation, please?
->Customer says that if this is specification of BQ24780S, it is no problem.
Customer just wants to know the reason of this situation.

Best regards,
Shimizu

over 9 years ago

0 masahiko shimizu over 9 years ago

Guru 11235 points

Hi ,

How is the progress?

Best regards,
Shimizu

0 Wang5577 over 9 years ago in reply to masahiko shimizu

TI__Guru 56650 points

I saw the Vsys also had a glitch at that point. So, I think a load transient makes ACN higher than SRN which turns off the BATFET.

ACN to SRN COMPARATOR (ACN_SRN) threshold is shown in spec table "ACN to SRN COMPARATOR (ACN_SRN)". If ACN is higher than SRN 220mV, the BATFET could be turned off.

Thanks,
Wang

0 masahiko shimizu over 9 years ago in reply to Wang5577

Guru 11235 points

Hi Wang,

Thank you for your advice.

I confirmed SRN and ACN voltage at dropping BATDRV.

Please see the below picture.

These voltage is flat at dropping BATDRV.

Have you come up to the other as cause of this issue?

Best regards,

Shimizu

0 Wang5577 over 9 years ago in reply to masahiko shimizu

TI__Guru 56650 points

Today, I duplicated it on my bench when I slowly changed VBAT around 7V. If I keep VBAT stable or other VBAT voltage, BATDRV doesn't have that glitch.

0 masahiko shimizu over 9 years ago in reply to Wang5577

Guru 11235 points

Hi Wang,

Thank you for your support.
and I'm sorry many times.

I confirmed how to reproduce at EVM to my customer.
Customer does not change EVM contents from default setting.
I show the method at below.
Could you re-experiment with the method of below, please?

[Procedure]
1. BAT pin is supplied 7V by DC stabilized power supply.
2. SYS pin is connected to electronic load which is CC mode.
3. Load is up slowly(0A -> 5A)
4. then, BATDRV dropping will occur.

Best regards,
Shimizu

0 masahiko shimizu over 9 years ago in reply to masahiko shimizu

Guru 11235 points

Hi Wang,

I'm sorry, I know you must be busy.

How is the progress?

Could you experiment at above procedure, please?

Best regards,

Shimizu

0 Wang5577 over 9 years ago in reply to masahiko shimizu

TI__Guru 56650 points

I can duplicate it. Also, show it to our designer. bq24780s has that drop around 7V VBAT. I think it is caused by the internal charge pump cirucit switching from internal source to BATSRC at 7V VBAT.

Regards,

Wang

0 masahiko shimizu over 9 years ago in reply to Wang5577

Guru 11235 points

Hi Wang,

Thank you for your support.
I wait the designer's answer.

Best regards,
Shimizu

0 masahiko shimizu over 9 years ago in reply to masahiko shimizu

Guru 11235 points

Hi Wang,

Did you have reply about this issue from designer?

Best regards,
Shimizu

0 masahiko shimizu over 9 years ago in reply to masahiko shimizu

Guru 11235 points

Hi Wang,

How is the progress?

Best regards,
Shimizu

0 Wang5577 over 9 years ago in reply to masahiko shimizu

TI__Guru 56650 points

Let me check designer again.

0 masahiko shimizu over 9 years ago in reply to Wang5577

Guru 11235 points

Hi Wang,

How is the progress?
I want to close this issue.
Please give me answer.

Best regards,
Shimizu

0 Wang5577 over 9 years ago in reply to masahiko shimizu

TI__Guru 56650 points

Would you send your email address to wang-li@ti.com? We can have an offline discussion.

Thanks,

Wang

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BQ24780S BATDRV drops around VBAT=7V