BQ40Z50: the back up time while PBI connect with different capacitor

Hello,

The datasheet specifies the output resistance. With this info, we can calculate the RC. The fall time is in the order of milliseconds. ~10ms.  

Kailun Liu said:

Another question is, there is no PBI in BQ41Z50, is there any consideration of this?

We collected information about this and most of the customers were not using this pin as backup. So, it was decided to remove the PBI. 

Hi Kailun,

I think it is ok to GND the PBI pin. Here's a thread which discusses about this. 
https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/738494/bq40z50-bq40z50-bq40z60-bq40z80---tapping-pbi-for-enable-pin-function

Hi Kailun,

The 10ms fall time is independent from the operating mode. Once shutdown is triggered, the 10ms fall time still applies.

The question might be how soon shutdown will trigger depending on operating modes. Assuming that the shutdown is based on cell voltage, If the gauge is in SLEEP mode, it will have to wake and sample the voltage (voltage < shutdown_voltage_threshold) to then enter shutdown mode. 

Please visit TRM section 5.4 for all different types of shutdown. https://www.ti.com/lit/ug/sluubk0b/sluubk0b.pdf