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BQ24610: PG LED flashing

Bernhard Suppan
Prodigy 230 points
Part Number: BQ24610

When i switch on the power source the PG LED is lighting up. after about one second, it starts to flash with a freuqency of about 10 Hz.
Does this indicate that VCC is invalid? I didn't find anything about flashing in the datasheet.
VCC is at 24V

  • 0
    TI__Mastermind 20570 points

    Can you probe VCC and VSRN on the scope? VCC voltage needs to be than the SRN voltage

    Can you also provide schematic?

  • 0 in reply to Jing Zou
    Prodigy 230 points

    I found out what is causing the problem. It is the thermistor. When I disconnect it everything works fine.

    So I put a power source instead of the thermistor and varied the voltage. At about 1.3V the PG LED starts to flash and the state 1 LED starts to light. If I reduce the voltage it stops at about 1.1 V.

    Here is the part of the Circuit:

  • 0 in reply to Bernhard Suppan
    Prodigy 230 points
    More details about this Problem:

    Voltage without thermistor: 3.2V
    Between 2.4V and 1.1V PG starts to flash and State 1 starts to light. above or underneath this voltage area only PG is lightning.
  • 0 in reply to Bernhard Suppan
    TI__Mastermind 20570 points

    PG behavior should not relate to TS pin. TS 3.2V is >VLTF which charge is suspended. STAT1 and STAT2 should both be off. Between 2.4 and 1.1V charge is allowed, if device is charging, then STAT1 should be on. So the charge status pins behave correctly. However, PG pin should not relate to this. Does this behavior happen on multiple boards? Have you tried with a different IC on the board?

  • 0 in reply to Jing Zou
    Prodigy 230 points

    I only have one PCB and only tried it with one IC yet.
    I just checked the marking on the IC and I am not sure if it is the correct one. The Marking on the IC is: "QAS TI 791 CGXH" or "OAS TI 791 CGXH" (Not sure if a Q or a O). I searched the marking on the internet but didn't find anything. Can you tell me if this is the correct IC? What should be the marking?

  • 0 in reply to Bernhard Suppan
    TI__Mastermind 20570 points

    OAS is the correct marking. you can find marking info at the end of the datasheet. I am wondering if your IC is damage that is why I have asked if this issue is observed on multiple IC. You can request free sample on ti website.

    Are you testing on the ti EVM ?

  • 0 in reply to Jing Zou
    Prodigy 230 points
    No. I am testing it on my own PCB.
    I only have one PCB and replacing it will be a little bit of a struggle, so if you have any other advice for me, that would be great.
    Otherwise I have no other options than replacing it
  • 0 in reply to Bernhard Suppan
    TI__Mastermind 20570 points
    Can you share your scope capture on the issue and along with the full schematic?
  • 0 in reply to Jing Zou
    Prodigy 230 points

    The Schematic is not very different to the one in the datasheet.
    The scope pictures are attached.
    I measured each testpoint and the PG signal at the same time to make it esay to compare.

    Signals.zip

  • 0 in reply to Bernhard Suppan
    TI__Mastermind 20570 points

    ACDRV turning on and off is the reason for PG pin to flash. Can you probe VCC in comparison with SRN. 

    The schematic in the datasheet is the minimum components required. Please always use the EVM schematic as reference.

  • 0 in reply to Jing Zou
    Prodigy 230 points

    I measured the VCC, SRN and ACN signal in comparison to each other.

    3056.Signals2.zip

    I also replaced the IC and the PG LED is still flashing.

    There is not a big difference between the circuit in the evm and in the datasheet. There are more components in the circuit in the evm than in the datasheet, but not everyone of them is placed (some BOM quantities are zero)

  • 0 in reply to Bernhard Suppan
    TI__Mastermind 20570 points

    Do you have the battery connected? Why does SRN oscillate from 5V to 23V? 

    From the scope capture, you can clearly see that the VCC-SRN voltage is < 100mV. TI recommends an input voltage of at least 1.5 V to 2 V higher than the battery voltage, taking into consideration the DC losses in the high-side FET (Rdson), inductor (DCR), and input sense resistor (between ACP and ACN), the body diode drop of RBFET between VCC and input power supply, and battery sense resistor (between SRP and SRN).

    Can you please try to increase the input voltage and test again.

  • 0 in reply to Jing Zou
    Prodigy 230 points

    I solved the Problem
    I incerased the supply Voltage and it worked. It did't work because I configured it to charge the Battery with 25V but was supplying it with 24V.
    I always tought that it would just charge the battery with less voltage. That was my fallacy

    Thank you

    One last question:

    I want to follow the test procedure in the evm. In Chapter 2.4.1 it says that i should turn on the supplies and then increase the supply voltage to a maximum of 5V and the TS voltage to 1.8V. In that case the PG LED of my PCB would flash. Should that happen?

  • 0 in reply to Bernhard Suppan
    TI__Mastermind 20570 points

    Yes, because in your set up, the output regulation is set to 25V, and your input is only 5V. 

  • 0 in reply to Jing Zou
    Prodigy 230 points

    But shouldn't it be flashing on the EVM too? Because you apply 5V, but the Resistors R25 (909k) and R28(100k) are configured to charge a battery with about 21V (VBAT = 2.1V × [1+ R25/R28])