BQ78350: BQ78350-R1=BQ76940 Integration of charging and discharging application

Lenna Yan

Intellectual 1960 points

Part Number: BQ78350

Hi,

The current design for BMS output is using charging and discharging integration structure.

After the end of charging process, the charge MOSFET function of BQ78350 will be disabled. When the circuit dischaging, the current will flow through the body diode of charge MOSFET first. After the discharging current can be detected, the charge MOSFET will open again.

The bench test result shows it takes about 357ms from the discharging current detected to Charge MOSFET open. That is say, the current all flows through MOSFET's body diode during this 357ms.

Question: Is there a method to make the time shorter?

Regards,

Lenna

over 7 years ago

0 Batt over 7 years ago

TI__Mastermind 42535 points

Lenna,

This outside of the gauge depends on the gate cap of the FET you choose. So, yes, it can be reduced by choosing a different FET.

0 Lenna Yan over 7 years ago in reply to Batt

TI__Intellectual 1960 points

Batt,

You mean it's because the drive speed is too low, choosing a FET with smaller Qg can make the time shorter. The MOSFET's body diode conduction time is 357ms. I think the MOSFET turn on time is much smaller than 375ms.

Regards,
Lenna

0 Batt over 7 years ago in reply to Lenna Yan

TI__Mastermind 42535 points

Lenna,

Irrespective of that, you also have a fw component which is determined by the fw internal processes. Once the gauge's pin drives it low, then the fet will open, that time will still be indeterminate.

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BQ78350: BQ78350-R1=BQ76940 Integration of charging and discharging application