• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 63 subscribers
  • Views 159 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ24072T: No charge current but all conditions appear correct

Jim G
Intellectual 465 points
Part Number: BQ24072T

I'm attempting to validate my charger design using BQ24072T and having issues, not seeing any charging current.

My battery is a 1S4P, 3.7V nominal. For the test, I've discharged it to approximately 3.5V.

For the test, I keep EN1 and EN2 low to attempt 100mA charging.

My charger input is 5.0V DC. When I apply the 5V source, I can confirm that PGOOD pulls low as expected.

I then probe around the circuit:
    Vbat = 3.54V.
    Vin = 4.994V
   Vout = 3.74V
   
I then set CHG_CE low and probe CHG, and can confirm that it has pulled low and remains low which should indicate that the device believes it is charging.

I have a DMM in series with my battery to monitor battery current, and see none.
I then probe the voltage at Iset (which per the datasheet, the current out of Iset should reflect 1/400 of the actual charging current). My Rset resistor is 590ohms, and I measure 0.0V on the Iset pin of the charging circuit. This agrees with my external DMM - the charger IC appears to be telling me with the CHG signal that it is indeed charging, but no charge current is present.

I have also attempted trying different combinations of EN1 and EN2, but see no changes with any EN1/EN2 configuration.

I'd like to confirm the package markings here to make sure it's the right component, but cannot find package markings in the documentation.
My IC package shows 3 lines of text:
PAP
TI 878
A1PQ

I'll add some other configuration notes at the end here:
My Ilim is set to 1.5A with a 1.07k resistor, TD is connected to GND, and Rtmr = 72k

Questions:
Are there any other suggestions for what to check here to determine why the charger is not actually providing current?
Are these package markings for the BQ24072T correct?
Is my battery voltage not low enough to actually trigger charging, and if not, why is the charger indicating that it is actually charging with the CHG signal?

I've also just noticed datasheet section 9.3.12 Temperature Monitoring - my current battery pack does not have an NTC and I simply have a 10k resistor to GND attached to the TS input.
I see now for applications which do not require TS monitoring that it should be a divider which sets the TS input voltage to between Vcold and Vhot.
Does it seem like the low TS voltage could be the culprit here?

Thanks!

  • 0
    TI__Mastermind 23170 points

    Hi Jim,

    Thanks for all of the information! You've actually done a lot of the steps for checking why it's not charging:

    • Checked all voltages (VIN, VBAT, VOUT)
    • Verified EN1 and EN2
    • Verified /CHG and /PGOOD
    • Check voltage on ISET

    Based on what you've given, it would seem that the TS being pulled to ground is causing the device to believe it's operating outside of the temperature threshold. Without an NTC, you'd need to set the TS pin to 20% of the input voltage (in your case 5V means the TS pin should be 1V) to bypass this feature. It lets the device believe that it is still within operating temperature. 

    I will reach out to the right group regarding the packaging if this continues to be an issue. 

  • 0 in reply to Anthony P Pham
    Intellectual 465 points

    Hi Anthony,

    Thanks for your response. I was able to inject 1.0V directly onto the TS pin and observed that the charger sourced the Iset current (500mA) to my battery. It looks like that is the solution here.

    Jim