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BQ25756: BQ25756 REGN 5V OUOUT ISSUE

Swapnil
Intellectual 285 points
Part Number: BQ25756

Tool/software:

Hi ,

We are follow same BQ25756 EVM  sch for our design .When connected our design PCB   with BMS studio, we see DEVICE ACK ok & power good signal also ok ,but we can not get 5V REGN BUCK output . What should i do ? Kindly find attached sch for your reference .BAT_CHARGER _V0.pdf

  • 0
    TI__Genius 16370 points

    Hello Swapnil,

    REGN is powered by an internal LDO will turn on during charging or reverse mode. Is EN_CHG=1 and the CE pin pulled LOW?

    I'll look at your schematic later on this week and get back to you.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Intellectual 285 points

    Hi Ethan ,

    We already try this  EN_CHG=1 and the CE pin pulled to low  but same issue result found .No LDO output.

  • 0 in reply to Swapnil
    TI__Genius 16370 points

    Hello Swapnil,

    I have a few questions.

    Do you have any capacitors on VSYS? I can't find them.

    What's the voltage on DRV_SUP?

    I see REGN is connected to a connector leading outside the circuit. Is REGN attached to any other component?

    Can you also read the registers of the charger and send the file to me?

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Intellectual 285 points

    Hello Ehan ,

    There is no any cap on VSYS  &  voltage  DRV_SUP connected  REGN LDO ouput by using JP2 jumper setting.kinldy find attached register file . We have used same register on EVM board . this is working & we get ouput voltage 29V without BAT load.

    16 bit resister.txt 
    * Created: Fri Sep 06 15:43:52 IST 2024
*
* Format: Register Name  tab Character,\t  Register Address  tab Character,\t  Hexadecimal register value.
* BQZ Container: Charger_1_00-bq25756.bqz
*
Charge Voltage Limit	00	10
Charge Current Limit	02	640
Output Voltage Limit	04	00
Input Current DPM Limit	06	140
Input Voltage DPM Limit	08	348
Reverse Mode Input Current Limit	0A	640
Reverse Mode System Voltage Limit	0C	3E8
Precharge Current Limit	10	140
Termination Current Limit	12	A0
Precharge and Termination Control	14	0F
Timer Control	15	1D
Three-Stage Charge Control	16	00
Charger Control	17	C9
Pin Control	18	C0
Power Path and Reverse Mode Control	19	20
MPPT Control	1A	20
TS Charging Threshold Control	1B	96
TS Charging Region Behavior Control	1C	57
TS Reverse Mode Threshold Control	1D	40
Reverse Undervoltage Control	1E	00
VAC Max Power Point Detected	1F	00
Charger Status 1	21	08
Charger Status 2	22	80
Charger Status 3	23	00
Fault Status	24	00
Charger Flag 1	25	00
Charger Flag 2	26	00
Fault Flag	27	00
Charger Mask 1	28	00
Charger Mask 2	29	00
Fault Mask	2A	00
ADC Control	2B	60
ADC Channel Control	2C	0A
IAC ADC - Use Field View	2D	00
IBAT ADC - Use Field View	2F	00
VAC ADC	31	00
VBAT ADC	33	00
TS ADC	37	00
VFB ADC	39	00
Gate Driver Strength Control	3B	00
Gate Driver Dead Time Control	3C	00
Part Information	3D	12
Reverse Mode Battery Discharge Current	62	02
    8 bit resisters.txt 
    * Created: Fri Sep 06 15:44:20 IST 2024
*
* Format: Register Name  tab Character,\t  Register Address  tab Character,\t  Hexadecimal register value.
* BQZ Container: Charger_1_00-bq25756.bqz
*
Charge Voltage Limit	00	10
Charge Current Limit	02	640
Output Voltage Limit	04	00
Input Current DPM Limit	06	140
Input Voltage DPM Limit	08	348
Reverse Mode Input Current Limit	0A	640
Reverse Mode System Voltage Limit	0C	3E8
Precharge Current Limit	10	140
Termination Current Limit	12	A0
Precharge and Termination Control	14	0F
Timer Control	15	1D
Three-Stage Charge Control	16	00
Charger Control	17	C9
Pin Control	18	C0
Power Path and Reverse Mode Control	19	20
MPPT Control	1A	20
TS Charging Threshold Control	1B	9E
TS Charging Region Behavior Control	1C	57
TS Reverse Mode Threshold Control	1D	40
Reverse Undervoltage Control	1E	00
VAC Max Power Point Detected	1F	00
Charger Status 1	21	00
Charger Status 2	22	80
Charger Status 3	23	00
Fault Status	24	00
Charger Flag 1	25	00
Charger Flag 2	26	00
Fault Flag	27	00
Charger Mask 1	28	00
Charger Mask 2	29	00
Fault Mask	2A	00
ADC Control	2B	40
ADC Channel Control	2C	0A
IAC ADC - Use Field View	2D	00
IBAT ADC - Use Field View	2F	00
VAC ADC	31	00
VBAT ADC	33	00
TS ADC	37	00
VFB ADC	39	00
Gate Driver Strength Control	3B	00
Gate Driver Dead Time Control	3C	00
Part Information	3D	12
Reverse Mode Battery Discharge Current	62	02

  • 0 in reply to Swapnil
    TI__Genius 16370 points

    Hello Swapnil,

    Thanks for being patient with this. I'll get back to you next week on this.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Intellectual 285 points

    Hello Ethan ,

    We also try with connected 55uF/80V cap on VSYS .But same result found .No REGN LDO O/P

  • 0 in reply to Swapnil
    TI__Genius 16370 points

    Hello Swapnil,

    I can't find anything odd with your registers.

    I've looked at your schematic again and I have a few suggestions/questions about your schematic.

    • I'd recommend setting SW1/SW2 RC filters to DNP. These are the components R54, R55, C58, and C61.
    • Do you have an external gate drive or are you using REGN?
    • Are pin 33 and pin 32 tied together?
    • The SRN/SRP resistors (R67, R69) have to be 10Ω.
    • This shouldn't matter for your current issue, but I'd recommend shorting Mode to GND.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Intellectual 285 points

    Hello Ethan ,

    Thanks ,After connected pin 33 & 32 .We get REGN outout is 5V But again we are not geeting output voltage .

  • +1 in reply to Swapnil
    TI__Genius 16370 points

    Hello Swapnil,

    That's great. Now that you are getting REGN to be 5V out, can you send me your flag and status registers when you set EN_CHG=1? EVM should report a different error now that REGN is 5V.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Intellectual 285 points

    Hello Ethan ,

    We are accurately read VAC_ADC & VBAT_ADC voltages in GUI . But We can't read accurately IAC_ADC & IBAT_ADC . When Digital mulimeter & Input power supply source shows 1A current . IAC_ADC read value around 780mA .

  • 0 in reply to Swapnil
    TI__Genius 16370 points

    Hello Swapnil,

    We'll get back to you later on this week.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    TI__Genius 16140 points

    Hello Swapnil,

    We don't spec the accuracy of the ADC channels. The IBAT and IAC ADCs become accurate once the current gets beyond 5A. If these measurements are necessary, I'd recommend using a dedicated battery gauge or other meter to get an accurate measurement of the IAC, and IBAT.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Intellectual 285 points

    Hello  Christian ,

    When we set charging current 500mA ,precharge current 100mA ,termination current 50mA & after that charge enable  Battery start charging with 500mA current but after 20s or after sometime charging goes to 2A  ( We used 2A power supply ) .

  • 0 in reply to Swapnil
    TI__Genius 16140 points

    Hello Swapnil,

    This is most likely the watchdog timer, if you disable the watchdog timer do you see this issue?

    It seems the watchdog timer expired, and reset to the default charge current, 20A. Your supply can only provide 2A, so thats why charge current only goes to 2A.

    I recommend disabling watchdog timer, or sending the charge current value before the watchdog timer expires.

    Best Regards,

    Christian.

  • 0 in reply to Swapnil
    TI__Genius 16370 points

    Hello Swapnil,

    Thanks for working with us. Can you make a new E2E thread for this question?

    In the new thread, can you provide the register settings and any modifications made to the EVM?

    Best Regards,
    Ethan Galloway