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Original question:

BQ25628: BQ25628 Ship Mode

BQ25628: Problem with charging

Matthew Pediaditis
Prodigy 140 points
Part Number: BQ25628
Other Parts Discussed in Thread: USB2ANY, BQSTUDIO, , EV2400

Hi, we are facing a problem with the charging mode of the BQ25628 on a custom design (PMID is not used).
Although all the conditions are fulfilled (converter starts successfully, EN_CHG = 1, CE_N pin is low, no thermistor fault on TS, no safety timer fault), the device doesn't charge.
We have disabled the watchdog and have set all the voltage and current limits (reg0x02-re0x12). 
We have read the charger status and fault status registers. 
The CHG_STAT is 0x1 which indicates that the device is charging. However, the VINDPM_STAT is 0x01 (in VINDPM regulation) which is a bit suspicious as we expected 0x00 Normal mode.
No fault status recorded.
By reading the ADC conversions of the reg0x28-reg0x36, we see that the IBAT = 0 which means that the device isn't charging actually.   
Could you please provide any further information why the charging mode is not working properly ?

We have also purchased the bq25628 EVM board with the USB2ANY interface. But it doesn't seem to work with bqstudio. Can you suggest a way to explore the EVM board with USB2ANY?

Thanks!

  • 0
    TI__Mastermind 22065 points

    Hi Matthew, 

    Firstly, the GUI on BQSTUIDO for the BQ25628EVM board needs the EV2400 interface to function. The USB2ANY can be used to send individual I2C communications to the EVM, but is not compatible with BQSTUDIO.  

    Regarding your issue with charging can you help to share the hex value of all registers so I can review. Given the device indicates you are in VINDPM can you also help to measure VBUS voltage near the BQ25628 IC while you attempt to charge. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 140 points

    Hi, thanks for the help. Here are the register hex values:

    VBUS is 5V measured not exactly near the device but close.


    REG0x02_Charge_Current_Limit = 0x0100;
    REG0x04_Charge_Voltage_Limit = 0x0D20;
    REG0x06_Input_Current_Limit = 0x0320;
    REG0x08_Input_Voltage_Limit = 0x0E60;
    REG0x0C_VOTG_regulation = 0x0FC0;
    REG0x0E_Minimal_System_Voltage = 0x0B00;
    REG0x10_Pre-charge_Control = 0x50;
    REG0x12_Termination_Control = 0x10;
    REG0x14_Charge_Control = 0x06;
    REG0x15_Charge_Timer_Control = 0x18;
    REG0x16_Charger_Control_0 = 0xA0;
    REG0x17_Charger_Control_1 = 0x4F;
    REG0x18_Charger_Control_2 = 0x04;
    REG0x19_Charger_Control_3 = 0xC4;
    REG0x1A_NTC_Control_0 = 0x3D;
    REG0x1B_NTC_Control_1 = 0x25;
    REG0x1C_NTC_Control_2 = 0x3F;
    REG0x1D_Charger_Status_0 = 0x44;
    REG0x1E_Charger_Status_1 = 0x0C;
    REG0x1F_FAULT_Status_0 = 0x00;
    REG0x20_Charger_Flag_0 = 0x40;
    REG0x21_Charger_Flag_1 = 0x00;
    REG0x22_FAULT_Flag_0 = 0x00;
    REG0x23_Charger_Mask_0 = 0x00;
    REG0x24_Charger_Mask_1 = 0x00;
    REG0x25_FAULT_Mask_0 = 0x00;
    REG0x26_ADC_Control = 0x70;
    REG0x27_ADC_Function_Disable_0 = 0x00;
    REG0x28_IBUS_ADC = 0x002C;
    REG0x2A_IBAT_ADC = 0x0000;
    REG0x2C_VBUS_ADC = 0x1238;
    REG0x2E_VPMID_ADC = 0x122c;
    REG0x30_VBAT_ADC = 0x0F42;
    REG0x32_VSYS_ADC = 0x0F28;
    REG0x34_TS_ADC = 0x0228;

  • +1 in reply to Matthew Pediaditis
    TI__Mastermind 22065 points

    Hi Matthew, 

    The VBUS and VPMID ADC outputs indicate your input supply is approaching the VINDPM threshold (4.6V). With VBUS so close to VINDPM it appears the buck converter is off. You will need to determine what in your system is causing the 5V input to reduce to approx. 4.6V at VBUS. 

    In the short term you should be able to observe charging if you reduce the VINDPM threshold in REG08. I recommend to try lowering it to a value in the range of 4V. 

    Unrelated, but can you also clarify what you mean by "PMID is not used"? Does that mean you have no external components, including capacitors, connected at PMID? 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 140 points

    Thanks! it was related to VINDPM threshold as you mentioned. The forward voltage drop of a reverse polarity protection diode was the issue, reducing VBUS after the measurement point.

    Considering PMID, it is not used but the external capacitors are connected.

    The only missing thing is that the VBUS_FLAG does not seem to transition to 1, but maybe the register is read at the wrong time-point.

    Thanks again.

  • 0 in reply to Matthew Pediaditis
    TI__Mastermind 22065 points

    Hi Matthew,

    Great to hear the issue is resolved. Thank you for confirming the behavior was due to the VINDPM threshold and voltage drop along the input path to the charger IC. 

    Matthew Pediaditis said:
    Considering PMID, it is not used but the external capacitors are connected.

    Thank you for confirmation. Even when PMID is not used the external capacitors are required for operation. 

    Matthew Pediaditis said:
    The only missing thing is that the VBUS_FLAG does not seem to transition to 1

    We have not had other reports of issues with the VBUS_FLAG bit and I have verified it works as expected on a BQ25628EVM. Be aware it will transition to a 1 after input supply is connected or removed, but after register is read once it will return to a 0b. 

    Best Regards,

    Garrett