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BQ25672EVM: BQ25672 AC OVP

Pascal Provost
Prodigy 90 points
Part Number: BQ25672EVM

I  have a BQ25672EVM  connected to one PSU on VIN1, nothing on VIN2 et USB connector, one  5W 10ohm resistor between SYS pin and GND, one cell LiFePO4 battery on Battery port.

I would like to use UVB from Vin=4 to 7V.

I set VAC_OVP = 7V, Charge current=1A, Voltage Charge =3.75V and Cell=1S with TI Charger GUI.

Battery is partially charged.

First step Vin1= 5.0V, VBAT=3.5 IBAT=1A , VSYS=3.53V and Iload=0.353A.

I tune up Vin up to 7V. At 7V AC1_OVP is detected and BQ switches on Battery as active power source.

I tune down slowly Vin1. BQ switches back on Vin1 as active source. Charge is active .

I go on tuning down and at 6V BQ switches on Battery . Why?

The only way to force BQ to Vin1 again is to switch OFF/ON Vin1.

I expected that once OVP condition disappeared, Vin was the active source as long as Vin is between Vac_Present(2.8V) and Vac_OVP(set to 7V).

May you please explain BQ behaviour and recommand one regsiter setting for my target application ?

Regards

  • 0
    TI__Guru**** 153016 points

    HI Pascal,

    I do not expect that behavior.  What do the status and fault registers in REG0x1B -0x27 report if you do a read all registers immediately after the BQ switches off the battery.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Guru**** 153016 points

    HI Pascal,

    I just tested with an EVM and do not see the issue.  I started with the IINDPM limit at 1.4A EVM default setting.   What is your IINDPM setting?  Is the external ILIM pin still enabled (REG0x14b1=1)?  The charger reperforms D+/D- and poor source detection after exiting OVP.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 90 points

    Hi Jeff,

    Here is my configuration at start of test:

    IINDPM limit at 1.42 A  EN IINDPM Register Disabled

    ILIM from ICO 1420mA EN ICO disabled

    EN ILIM pin activated

    VAC OVP=7V ( my own setting)

    ABS VINDPM 6.0V

    D+/D- left unconnected

    Reg14 0x001A so Bit1 is set to 1

    Reg 13 0x13

    Reg 1B 0x000B

    Just after exiting OVP condition, Vin1 is active source but when I go on reducing Vin1 voltage slowly downto 6.0V Battery becomes active source. This is my concern.

    Regards

  • 0 in reply to Jeff F
    Prodigy 90 points

    Hi Jeff,

    Beginning of test Vin1=5.0V is acitve source and REG1B to 21 are 0x000B/0x00EA/0x0001/0x00C0/0x0000/0x0000/ all Flag Registers are 0x0000.

    During OVP conditions(Vin1=7V) battery is acitve source and REG1B to 21 are 0x0002/0x000A/0x0001/0x00C0/0x0000/0x0001/ all Flag Registers are 0x0000.

    Just after exiting OVP, Vin1=6.35V is active source and REG1B to 21 are 0x000B/0x006A/0x0001/0x00C0/0x0000/0x0000/ all Flag Registers are 0x0000.

    I reduce VIn1 to 6.1V battery is active source and REG1B to 21 are 0x004B/0x006A/0x0001/0x00D0/0x0000/0x0000/ all Flag Registers are 0x0000.

    I reduce VIn1 to 5V battery is active source and REG1B to 21 are 0x004B/0x006A/0x0001/0x00D0/0x0000/0x0000/ all Flag Registers are 0x0000.

    I make an OFF/ON on Vin1, Vin1=5V is active source REG1B to 21 are 0x000B/0x000A/0x0001/0x00C0/0x0000/0x0020/ and Flag Registers are 0x0000/0X0080/0X0000/0X0000/0X0020/0x0000.

    Regards,

  • +1 in reply to Pascal Provost
    TI__Guru**** 153016 points

    Hi Pascal,

    If set VINDPM = 6V and the apply VBUS=6V, the converter's duty cycle is reduced to zero because it thinks the input source has collapsed and can't provide any more power.  VINDPM is the lowest voltage you think that the input will drop and still provide power.

    Regards,

    Jeff   

  • 0 in reply to Jeff F
    Prodigy 90 points

    Jeff,

    OK for decreasing ABS VINDPM but I can only increase it on TI Charger GUI. Why?

    If I do not méake OVP, only power up with a 5V on VIN1 port , Vin1 is active , VBUS is 5V, charge is active no problem. VINDPM doesn't seem to be taken into account. Why?

    Regards,

  • 0 in reply to Pascal Provost
    Prodigy 90 points

    Hi Jeff,

    If I understand , when exiting OVP VAC becomes present again and VINDP is recalculated so just below 7V.

    When Vac comes back to its nominal value (5V in my case) it  is under VINDPM so detected as not PRESENT.

    It is a nonsense.

    Is there a way to inhibit VINDPM ?

    I haver other questions about VINDPM but will open a specific topic about this function.

    Regards,

  • 0 in reply to Pascal Provost
    TI__Mastermind 35265 points

    Hello,

    If you come out of OVP, the VINDPM will be recalculated according to Section 8.3.4.4 of the datasheet. As you continue to drop the input voltage, the VINDPM will not adjust along with it. The host will need to set it according to the application.

    I am looking into the TI Charger GUI issue you are seeing.

    Thanks,

    Mike Emanuel

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