bq76940 disable CHG output on SCD or OCD

Jessica Riley1

Other Parts Discussed in Thread: BQ76940, BQ78350-R1

Hello,

Is it possible to configure the bq76940 to disable both the CHG and DSG outputs on a short circuit or overload condition?

From the datasheet it looks like it can only be configured to disable the DSG output, but the bq78350-R1 user guide says it can configure it to turn off both (Section 3.1.4 of the bq78350-R1 user guide, bit setting [DC_CHG_OFF]). I'm not using the bq78350-R1 as my host controller, but if it can configure the AFE to function in this way, can I do the same with my host controller?

Thanks,

Jess

over 9 years ago

0 Vish Nadarajah over 9 years ago

TI__Expert 6085 points

During OCD or SCD faults, DSG_ON-->0 ; but need to bring CHG_ON--->0 , so that the load detection circuits is activated. Yes, you should be able to perform this.

0 Jessica Riley1 over 9 years ago in reply to Vish Nadarajah

Intellectual 280 points

Does that mean it can only be done via an additional command from the host? I was hoping for hardware setting which would provide an automatic response like for the discharge switch, so the delay in turning off the CHG switch would match the fast response of the SCD and OCD. If an extra command from the host is required, there is the additional delay of the I2C communication back and forth before the CHG switch will be disabled.

0 Vish Nadarajah over 9 years ago in reply to Jessica Riley1

TI__Expert 6085 points

The existing "hardwired" logic is restricted to *only* disable the DSG FET in cases of OCD or SCD fault. However, in your application, if the need mandates, external circuit can pull the CHG pin to GND without affecting the IC. Continuous current of 3mA out of the pin is allowed.

0 Jessica Riley1 over 9 years ago in reply to Vish Nadarajah

Intellectual 280 points

Thank you for the suggestion. Is it possible to drive the DSG output in the same way?

0 Vish Nadarajah over 9 years ago in reply to Jessica Riley1

TI__Expert 6085 points

I see no reason why not. But before I commit to the functionality , will need to confirm on the bench and current.

0 Jessica Riley1 over 9 years ago in reply to Vish Nadarajah

Intellectual 280 points

Thanks Vish. That would definitely be a "nice to have" if the circuit can handle it.

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bq76940 disable CHG output on SCD or OCD