BQ24079QW-Q1: Odd behaviour while testing

Chiara Belfanti

Part Number: BQ24079QW-Q1

Tool/software:

Good morning,

I'm sorry to bother you all but, unluckily, I had some problem while testing your device (probably I made some errors in the schematic but I can't find where things went wrong).

I have a voltage input of 6V and a battery of 3.3V (not fully charged or it would be 4.1V) but I get 3.6V as voltage output and the battery doesn't get charged.
I thought it could be a problem with the current drained by the devices seen as load but the value continues to be the same even when I remove all the load.

Any idea what the mistake could be?

Thank you for your support!

Regards,
Chiara

2 months ago

0 Garrett Kreger 2 months ago

TI__Mastermind 27575 points

Hi Chiara,

Thank you for reaching out via E2E. I have reviewed your schematic and have the below comments.

-Pin 2 BAT appears to be floating. Both pin 2 and pin 3 need to be connected to same output node for battery connection.

Beyond this your schematic looks good.

Please help to check if connecting pin 2 to pin 3 resolves your charging issue.

If it does not I have the following follow-up questions

1)What is the OUT pin voltage when 6V input is connected?

2)What is status of PGOOD and CHG LEDs at the time when you are unable to observe charging?

Best Regards,

Garrett

0 Chiara Belfanti 1 month ago in reply to Garrett Kreger

Prodigy 20 points

Thank you!

It seems that was the problem. I now see the battery charging and the output voltage at 5.4V.
While charging, though, I see the the PGOOD led ON and the CHG led OFF and while there's only the battery (Vin=0) both led are OFF (and I see the battery voltage at the output as expected). Is this the right behaviour? I understood that the PGOOD should be up only when the battery is completely charged.

Best regards,

Chiara

+1 Garrett Kreger 1 month ago in reply to Chiara Belfanti

TI__Mastermind 27575 points

Hi Chiara,

Great to hear the recommended change resolved the charging issue.

Chiara Belfanti said:
While charging, though, I see the the PGOOD led ON and the CHG led OFF and while there's only the battery (Vin=0) both led are OFF (and I see the battery voltage at the output as expected). Is this the right behaviour?

The PGOOD status indicator relates to input power source rather than battery charging status. PGOOD will pull low, turning on the LED, when a valid input source is connected. This is described in the Pin functions table on datasheet page 4. CHG LED will be on during charging and then turn off when battery is completely charged.

Please refer to datasheet section 9.3.5.5 for more details on PGOOD and CHG status indicators.

Best Regards,

Garrett

Power management

Power management forum

BQ24079QW-Q1: Odd behaviour while testing