BQ78350-R1A: Pre-discharge with BQ76930 + BQ78350-R1A+ BQ76200

LOIC REBOUSSIN

Expert 1620 points

Part Number: BQ78350-R1A
Other Parts Discussed in Thread: BQ76930, BQ76200, BQ78350

Tool/software:

Hi teams,

We have a design with AFE BQ76930 + gasGauge BQ78350-R1A with Fetdriver BQ76200.

Charge and dicharge FETs are managed by the AFE BQ76930. The pre-discharge is managed by the GG BQ78350-R1A.

We have a delay problem between the PDSG Fet and the DSG Fet command.

After pre-discharge delay, we observe that PDSG Fet turns OFF before the DSG Fet switch ON. Moreover the PDSG Fet is turns OFF 1.1ms before DSG Fet. You can see scope capture above,

This is problematic, because the PDSG Fet explodes with DI/DT due to DSG Fet doesn't close before PDSG Fet opens.

Can you suggest a fix ?

My understanding is that the I²C DSG command is sent too late to the AFE.

Best ragerds,

Loïc

1 month ago

0 Dominik Hartl11 1 month ago

TI__Guru 55996 points

Do you mean PCHG instead of PDSG? Please explain your sequence in detail. The bq78350 doesn't have pre-discharge FET control.

0 LOIC REBOUSSIN 1 month ago in reply to Dominik Hartl11

Expert 1620 points

Dear Dominik,

I speak about PDSG (pre-discharge). The BQ78350 have pre-discharge FET control since release 2.

The scope is about the end of Pre-discharge.

0 LOIC REBOUSSIN 4 days ago in reply to LOIC REBOUSSIN

Expert 1620 points

Do you confirm on your side?

0 Dominik Hartl11 4 days ago in reply to LOIC REBOUSSIN

TI__Guru 55996 points

The thread listbq78350-R1A: "We have a design with AFE BQ76930 + gasGauge BQ78350-R1A with Fetdriver BQ76200."

Please specify the exact version that you use. I answered for the R1 version as listed in this thread.

0 LOIC REBOUSSIN 3 days ago in reply to Dominik Hartl11

Expert 1620 points

I'm using BQ78350-R1A programmed with soft ware release V3 (BQ78350-R3 firmware, Version: R3-V3.00 Release date: 13 Jan 2023).

Sorry, I can't select BQ78350-R3 in the thread listbq.

Loïc

0 Dominik Hartl11 3 days ago in reply to LOIC REBOUSSIN

TI__Guru 55996 points

Thanks for the clarification.

I checked the R3 FW and it doesn't look like there's a way to change this. The FW instructs the AFE to turn on the DSG FET with the same instruction as turning off the PDSG FET (so this is atomic and not split up into separate commands). So if this leads to a 1.1ms delay between PDSG off and DSG on then this can't be configured away.

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BQ78350-R1A: Pre-discharge with BQ76930 + BQ78350-R1A+ BQ76200