BQ76972: 16S 200A low side BMS- BQ76972

Anatya Vallabh

Part Number: BQ76972

Tool/software:

Team , can you please help us out with the feedback on the below query shared by our customer-

We are designing the 16S 200A low side BMS. In that we have some questions which are mentioned below.

1) If We use our BQ76972 at the lower side, what will be the effect on the LD(load detection pin)? Please suggest it to us.
2) If We use our BQ76972 at the lower side, what will be the effect on Pre-Discharge functionality? Please suggest it to us.
3) Could you please suggest us the charging detection functionality for lower side BMS?
4) General query: Which core functionality will get affected if we use BQ76972 with Low-side mosfets?

Thanks

Anatya

9910522774

over 1 year ago

0 Thomas Rainey over 1 year ago

TI__Expert 4320 points

Hello Anatya,

1) Additional circuitry will be needed in order to control the LD function when using low-side configuration. For information and a example circuit is provided to help with low side configuration in section 7 Controlling LD of the Using Low-Side FETs with the BQ769x2 Battery Monitor Family application note.

2) To use precharge and predischarge with a low-side implementation a circuit is needed to translate the voltage from the high side to the low-side FETs. For information and a example circuit is provided to help with low side configuration in section 8 Precharge and Predischarge for Low-Side FETs of the Using Low-Side FETs with the BQ769x2 Battery Monitor Family application note.

3) Section 7 Controlling LD of the Using Low-Side FETs with the BQ769x2 Battery Monitor Family application note has information about charger detection to recovery from OCD.

4) The main core functionality affected by low-side FET configuration is communication. When the FETs are turned off the battery becomes isolated from the PACK-/Load ground causing reference for communication to be lost. This can be overcome with an isolator, if the customer needs to communicate with the device when the FETs are off. For more information on considerations for low-side FET configuration you can refer to the Using Low-Side FETs with the BQ769x2 Battery Monitor Family application note.

Best regards,

Thomas Rainey

0 Aniket Mahajan over 1 year ago in reply to Thomas Rainey

TI__Genius 15046 points

Hello Thomas,

Thanks for your response.

Customer has a follow up query regarding this:

Will the charger detect functionality get affected due to a low-side configuration?

Please explain how to implement the charger detect functionality in such a case.

Thanks and regards,

Aniket Mahajan

0 Thomas Rainey over 1 year ago in reply to Aniket Mahajan

TI__Expert 4320 points

Hello Aniket,

Important pins effected and the use of charger detection:

Wakeup from SHUTDOWN, such as when a charger is attached.
Charger detection in DEEPSLEEP

PACK

Measured voltage on this pin is used to detect charger attach, which then is used in OCC recovery, also when waking from SLEEP mode, also when delaying voltage-based SHUTDOWN.

The LD pin can still be used in the low side with additional circuitry. The PACK pin is tied to BAT not allowing charger detection. However, I good reference would be: https://www.ti.com/tool/TIDA-010216 this reference design has a wake up when charger is detected function.

You can also refer to this E2E: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1067700/bq76952-low-side-design-sleep-mode-charger-detection that asks a similar question.

Best regards,

Thomas Rainey

Power management

Power management forum

BQ76972: 16S 200A low side BMS- BQ76972