bq25504

david sun

Intellectual 330 points

Other Parts Discussed in Thread: BQ25504, TPS61020, TPS3839

Hello, Dear TI support,

in bq25504 data sheet, "Battery Status output - can be used to enable or disable system loads" what is this mean.

also at Page 14, 8.4.2 Main boost Charger enabled (...) and EN# = LOW,

where is this EN#.

I will use this chip as a back up booster only when the battery goes lower than 0.9V, there is another booster(TPS61020) in parallel

with bq25504, in default mode, TPS61020 works, bq25504 disabled. if the voltage is lower than 0.9V, ( TPS61020 disabled).

then bq25504 start to work to use the rest of the engineer in the battery. I hope to put this chip in disable mode to consume as less

power as possible. couldn't figure out how to control it.

thanks,

David

over 10 years ago

0 Jeff F over 10 years ago

TI__Guru**** 166916 points

There is no EN pin for the bq25504. The battery status output (VBAT_OK) is used to signal system loads connected to VSTOR or VBAT. I suggest you use a series PFET between the power source and VIN_DC pin to remove the source from the bq25504. You could use the TPS3839 comparator to drive the gate of the PFET.

0 david sun over 10 years ago in reply to Jeff F

Intellectual 330 points

Hi Jeff

if I put a PFET in series, let assume it is about 30mOhm, will it reduce the efficiency by half? because we have controller independent to this chip in our system. this chip will be used only as an back. can I use an external signal to drive the VBAT_OV to put the chip in sleep mode?

Sincerely

David Sun

0 Jeff F over 10 years ago in reply to david sun

TI__Guru**** 166916 points

The bq25504's internal FETS will likely still dominate the resistive loss even with a 100mohm PFET.
Although I have not tested it, you should be able to pull the VBAT_OV pin to VSTOR, which will prevent the IC from switching, as long as VSTOR > VSTOR_CHGEN~=1.8V. There could be as much as a 64ms delay because BAT_OV is only measured every 64ms.

0 david sun over 10 years ago in reply to Jeff F

Intellectual 330 points

Hi Jeff

we don't care the delay, we only care the sleep current, what is the current leakage of this chip if it is not switching.

0 Jeff F over 10 years ago in reply to david sun

TI__Guru**** 166916 points

This chip is powered from its output, VSTOR. Per datasheet spec I(VSTOR) in OV condition, the IC will consume 570nA typical, 1400nA maximum over temperature.

0 david sun over 10 years ago in reply to Jeff F

Intellectual 330 points

if that is the case, I will buy a evaluation board and do some measurement, thanks

Power management

Power management forum

bq25504