BQ2972: My circuit not triggering properly while charging

Hi Bala,

Did you use the total resistance of the 2 FETs in your calculations? If each FET has 130 mOhms for Rdson, then it takes (0.130V / 260 mOhm) = 500 mA to trigger OCD, and it takes (-0.100V / 260 mOhm) = -384 mA to trigger OCC.

Best regards,

Matt

Hi Matt,

the FET im using has 70mOhms rdson each so it is 140mOhms in total. The problem is sometime COUT not turning on properly. whether this is because of the FET i choosed or do i need to look other related circuit. 

Hi Bala,

The circuit looks okay in that case. Does COUT not turn on at all or is it turning off unexpectedly? 

Hi Matt,

Its not turning on at all sometime while powering on.

Hi Bala,

The DSG FET may have this issue at power-up as noted in the datasheet, but this should not be the case for the CHG FET. See the datasheet note below. What cell voltage do you measure?

Hi Matt,

is it ok connect this V- pin to VSS all the time ? Will it create any issue ? Please advise.

I think the datasheet means to just short these pins briefly to enable the discharge FET.