unreal over current faults on the BQ77910

Ran Aloni

Other Parts Discussed in Thread: BQ78PL116

Hi All,

I have a serious issue with BQ77910,

I am using the BQ77910 EVM, an E load and power supply, the same as I did when I tested the BQ78PL116 so I'm sure that they are working properly.

I keep getting Over current faults, even when I'm Discharging with 0.5A.

the higher the current the shorter time till OC fault.

I checked the voltage upon the Rsense and it is steady as far as I can see and well below the trip level.


RSENSE = 1 mOhm

OCD delay = 2 s

OCD trip level = 35mV so 35A.

a steady 9KOhm resistor as NTC to eliminate this issue.

after a try a few times, it start discharging OK, with no noticeable reason.

do you think the communication could interfere some how? ESD? 

what could be the problem?

over 14 years ago

0 WM5295 over 14 years ago

TI__Guru 54715 points

Communication is most likely the problem. The bq77910 is a standalone protector, its normal operation does not have communication. Communication with the device is a disruptive event. To communicate with the device ZEDE is set high which sets delay to zero and essentially removes any noise filtering, so very narrow voltage noise voltages on the sense pins may trip the current faults. It is best to evaluate the response behavior without communication, then if there is question as to the type of fault, poll to see the status. You may also see the FAQ item: http://e2e.ti.com/support/power_management/battery_management/w/design_notes/1380.aspx

(link changed 8/10)

0 Ran Aloni over 14 years ago in reply to WM5295

Expert 2386 points

thanks,

this is what I imagined to be the problem.

Power management

Power management forum

unreal over current faults on the BQ77910