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BQ24130: Output Voltage Not Consistent

Part Number: BQ24130
Other Parts Discussed in Thread: BQ24133

Hello,

Can you please advise if the below behavior is normal? Do we expect the output voltage to collapse with no cell connected? The status LED is telling me there is an issue:

  • The customer has a bq24130 EVM with no rework done.
  • The input voltage is 12V
  • The output is set to Single Cell (4.2V)
  • There is charged cell connected to the output
  • Multimeters are connected to the input at J1 and the output at J2
  • The output voltage is equal to the cell voltage, between 3-4V in this case.
  • The status LED is on
  • If the cell is removed the charge voltage falls to 0.8V
  • The status LED starts blinking

Any tests the engineer can try on their bench to identify the issue are appreciated! Thank you,

Regards,
Ryan B.

  • Hi Team,

    I now realize the flashing status LED was because the TS pin wasn't connected to the battery's NTC.

    However, the customer also notices the output voltage can get dangerously high as well. See the below table for a sequence of tests they ran with two cells (denoted Cell A and Cell B).

    Steps Cell Initial Cell Voltage TS Source Charger Output Voltage After Cell Connected (J1) LED Blinking?
    1 Disconnected - EXT 0.85V YES
    2 A 3.23V EXT 3.88V NO
    3 B 3.16V EXT 3.68V NO
    Cell B Disconnected and Charged Up
    4 B 4.10V EXT 10.93V NO
    5 B 4.10V INT 10.93V NO
    Cell B Disconnected and Discharged
    6 B 3.24V INT 3.70V NO
  • Hi Ryan,

    Can you provide scope shots of when the output voltage is at 10.93V (look at VIN, VBAT, VSW, and VSTAT)? Also, verify the voltage at VREF, CELL, BAT, AVCC, REGN. Did you mean you measure at J2 at the VBAT?

    CMOD and ISET1 also need to be controlled in order to have a good charging profile. When you are done charging at 4.2V (charging current goes close to 0mA), you should pull ISET1 low to disable charging (termination). The precharge to fast charge threshold is around 3.0V for lithium ion, CMOD is used to control this threshold (pull low for precharge, pull up to VREF for fast charge).

    I recommend using bq24133 if you cannot programatically change CMOD and ISET1.

    Regards,
    Steven
  • Hi Steven,

    Yes my fault, I meant to say J2.

    I have asked to customer to respond here once they try your recommendations.

    Regards,
    Ryan B

  • Hi Ryan,

    Any update on this?

    Regards,
    Steven