BQ24292I: body diode of BATFET

K.Yaita

Part Number: BQ24292I

Hi Team,

Is there body diode between BAT and SYS as the following?
The block diagram of datasheet doesn't show it cleary so I would like to confirm it.

Best Regards,
Yaita / Japan disty

over 7 years ago

0 Joel Hernandez II over 7 years ago

TI__Mastermind 25800 points

Hey Yaita-san,

There is body diode shown as the BATFET circuitry is more complex to allow for both charge and discharge phases and protections.

Regards,

Joel H

0 K.Yaita over 7 years ago in reply to Joel Hernandez II

Guru 29720 points

Hi Joel-san,

Thank you for your kind support.
Do you refer there is no path to supply system from battery when BATFET is "OFF" without DC source?
(In other words, is there possible case to supply system from battery when BATFET is "OFF" without DC source?)

Best Regards,
Yaita

0 Joel Hernandez II over 7 years ago in reply to K.Yaita

TI__Mastermind 25800 points

Hey Yaita-san,

No, when the BATFET is turned off, the path to the SYS pin is cut off. SYS voltage rail will lose power if there is no DC source AND BATFET is off.

Regards,
Joel H

0 K.Yaita over 7 years ago in reply to Joel Hernandez II

Guru 29720 points

Hi Joel-san,

Thank you for your support.
I would like to ask further question.

I believe BATFET turns off after the charging cycle is complete (full charge).
Is it possible case that SYS voltage rail lose power instantaneously although battery is still connected if we disconnect DC source at the timing?

Best Regards,
Yaita

0 Joel Hernandez II over 7 years ago in reply to K.Yaita

TI__Mastermind 25800 points

Hey Yaita-san,

The BATFET only turns off in the charging direction, meaning current will not flow into the battery. However, current can still flow in the reverse direction to support the SYS pin. If you remove the adapter, the voltage still remains from the BAT to SYS, and therefore the rail is not lost.

Regards,

Joel H

0 K.Yaita over 7 years ago in reply to Joel Hernandez II

Guru 29720 points

Hi Joel-san,

The datasheet shows BATFET can be forced off by the host through I2C REG07[5] and there is no path to charge or discharge the battery in REG07[5]=1.
On the other hand, the BATFET only turns off in the charging direction if we remove the adapter when charging cycle is complete (full charge) as you refered.

So I understood there is different state although BATFET is "OFF" in both case.
Is my understand correct?

Best Regards,
Yaita

0 Joel Hernandez II over 7 years ago in reply to K.Yaita

TI__Mastermind 25800 points

Hey Yaita-san,

That is correct. The charger needs to be able to immediately support the system power then the input is removed if the input source is removed.

Regards,
Joel H

Power management

Power management forum

BQ24292I: body diode of BATFET