BQ24618 don't charge with VCC lower 5V

Hi Daniil,

Are you measuring VCC at the pin, or at the input?

Is high side (almost) always on? Low side FET (almost) always off?

What is the value of your REGN Cap, and BTST cap?

yes, high is on, low is off, time to time pulses are appeared

At the pin.
REGN cap 1uF
BTST 0.1uF
Thanks for reply

Daniil,

Thanks for clarifying. Could you email me that image/schematic? I'm having some trouble reading the details to double check things. My email is d-wiest@ti.com

Daniil,

I have been looking at your schematic, and I think i may see what the issue may be.


I think what is happening is that your VCC is valid, so the converter is trying to switch to charge the battery. However, the voltage divider keeping the ACFET on does not satisfy the proper VGS (I noticed they are not the same for the application circuit in the datasheet) which causes the ACFET to turn off at this low input voltage. I think that if you tweaked the resistor divider for the ACFET will turn back on, and the charger will work as intended.

Right now, the charger is trying to regulate, but can't (ACFETs are off). This means that the charger will "fight harder" to get to the regulation voltage, resulting in the 100% duty cycle request.

David Wiest Jr,

I found my first problem: body diode voltage of acfet is 0.35V, thats way when Vin 5V, VCC is 4.65V. ACFETs are off.

Regards,

Daniil