BQ24610: BQ24610:

Hi,

We have probed the VCC pin when AC is absent.

And the battery voltage 7.8V is coming there. The internal diode on the reverse FET is passing the battery voltage to VCC pin.

Whether the VCC is required while AC is not there?

Can we use MOSFET without flyback diode?

We have to use adapter present future of the IC. for that we are using PG pin.

Please help us to solve the issue ASAP.

Regards,

Shafeeq

Hi Shafeeq,

      Can you take a waveform on adapter plug-in, where you monitor PG, VCC, SRN? Trigger on VCC rising and have a time scale of about 4ms. By flyback diode, are you referring to D10? When adapter is not present, it is expected that VCC voltage will be SRN - body diode voltage drop, however this is still considered an invalid VCC as it does not satisfy SLEEP condition.

Hi,

I have given pullup to the PG pin to VREF.

When I probed the VREF while AC is absent, it is not generating. Whether this is the expected condition or not?

And I have removed the pullup and tested. That time it is working fine.

But as per the datasheet, PG is an open-drain output. I couldn't understand, how it is getting high without pullup?

Regards,

Shafeeq

Hi Shafeeq,

        Open-drain output means there is an internal FET with a connection to GND as shown in the functional block diagram in the datasheet. When valid VCC, this FET will be driven closed, and current can flow lighting the LED, but with invalid VCC this FET would be open so no current would flow and LED would not be lit.

VREF is expected as VREF is present when VCC>UVLO and not in SLEEP, so when you remove the adapter VREF would not generate. What do you mean by remove pullup and tested? In this test, you de-soldered R114 and probed PG? What voltage did you observe?

Hi kedar,

I removed r114 and tested. So that time when AC is present, PG pin shows 0 and when AC is absent PG pin show 1. As it is an open drain output, when AC is absent the transistor will not turn on and PG pin will be  in tristate condition. And when AC is absent, i probed the PG pin and I got 3.29 V on PG pin. I couldn't understand that how this pin goes high without internal or external pullup.

Is this an unexpected condition? Please confirm.

As VREF will not generate while invalid VCC, Whether I have to give pullup to other 3.3V available in my board for getting an high signal to processor while AC is absent?

Please suggest.

Thanks & Regards,

Shafeeq