BQ25616: Device does not output anything when VBus is connected but gives a power when BAT is connected

Isaac Atia-Abugbilla

Part Number: BQ25616

Tool/software:

I have a one cell battery charger using BQ25616 which is connected to some load. The device accepts 12v input with Ilim set to 2.5A through Vbus to charge the battery and power the rest of the system. However, when I do connect the input 12v, I get now output and the PG and PMID pins indicate no voltage when I test with an oscilloscope. However, when I remove Vbus input and replace with a battery connected to BAT pin, I do get an output. Is the device fried or is there anyway to salvage this. I have provided a reference schematic.

7 months ago

0 Michael Emanuel35 7 months ago

TI__Mastermind 40375 points

Hello,

There is potentially too little resistance on STAT and PG/ pins. The ABS MAX is 6mA. Assuming 0.7V drop on diode for STAT from 4V, 11.8 mA of current goes through the open-drain, potentially damaging it. Similar logic goes for PG/ pin.

Regards,

Mike Emanuel

0 Isaac Atia-Abugbilla 7 months ago in reply to Michael Emanuel35

Prodigy 30 points

Does that mean the device is fried? In that case why do I get an output only when a battery is connected?

EDIT:

Upon further investigation, D7 has a Vf of 2.5v and using a resistor of 280ohm brings leads to a forward current of 5mA which is well withing the 6mA region. Also for D6, Vf is 1.8v; with a 360ohm resistor that should give about 6.1mA. In that case, the device should work fine, unless there is some other detail I am missing.

0 Michael Emanuel35 7 months ago in reply to Isaac Atia-Abugbilla

TI__Mastermind 40375 points

Perhaps those may be fine.

Where is the 4V pullup coming from? The pins are HIZ when they are not pulling low via open drain. In other words, they should be pulled up to the 4V rail. Maybe investigate what is going on with that rail?

Regards,

Mike Emanuel

0 Isaac Atia-Abugbilla 7 months ago in reply to Michael Emanuel35

Prodigy 30 points

the 4V rail is coming from Vsys.And that rail is fine as long as BAT is connected. However when I disconnect BAT then connect Vbus, I get no output from Vsys or SW. However the datasheet clearly states that even without battery or in the case of a severely depleted battery, as long as Vbus is connected, I should still get an output. In my case I am using a Vbat of 12v as the bq25616 can handle it according to the datasheet.