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BQ25672: the minimum value of input current and charge current

Henry Wang3
Genius 3365 points
Part Number: BQ25672
Other Parts Discussed in Thread: BQ25619, BQ25570, BQ25176

Hi Team,

My customer will use a solar panel with 5V/0.2~0.3A(1~1.5W) to the BQ25672 power input.

They would like to confirm the minimum value of input current and charge current.

May I know if the minimum value of input current just supports 0.1A at 5V-in, right? the minimum value charge current is 0.01A at 5-Vin, right?

  • 0
    TI__Guru**** 167146 points

    Hi Henry,

    IINPDM minimum regulated input current is 0.1A after startup.  0.2A is typically needed at startup.  Minimum regulated charge current is 0.05A.

    Regards,

    Jeff  

  • 0 in reply to Jeff F
    Genius 3365 points

    Hi Sir,

    You mean if the customer need to enable the MPPT function, the input current need 200mA at startup? How long is the startup time with 200mA?

    They would like to find a charge IC for a LiFePO4 battery(3.6V) and an input current of less than 100 or 200mA, may I know if there have any devices? Please advise us of the solution. Thanks!

  • 0 in reply to Henry Wang3
    TI__Guru**** 167146 points

    Hi Henry,

    There is always a startup inrush current that is a function of the capacitance at PMID and SYS and the load on SYS.  The customer can limit the charger's input current to 100mA using the ILIM_HIZ pin resistors but the startup will be slower. 

    If the solar panel open circuit voltage (VOC) is 5V then its VMPP ~=0.8*5V = 4.0V.  So any charger with VINDPM adjustable down to 4.0-V will work.  BQ25619 is another option.  In either case, charge must be disabled at power up using /CE pin because default charge voltage is 4.2V.  The host software then changes to the BATREG=3.6V and lowers VINDPM down to MPP threshold (~4.0V).

    Regards,
    Jeff

  • 0 in reply to Jeff F
    Genius 3365 points

    Hi Sir,

    Thank you so much for responding.

    May I know if the BQ25570 can or not support the LiFePO4 battery? if it can, I will ask the customer to remove the BQ25176.

  • 0 in reply to Henry Wang3
    TI__Guru**** 167146 points

    Hi Henry,

    The BQ25570 output can be set to provide constant voltage of 3.6V for LiFePO4 using the VBAT_OV pin resistors.  BQ25570 does not provide constant current charging or termination current cutoff  like BQ25176.  If the piezo device could provide higher output power and therefore high charge current, I would recommend using the BQ25176 to provide constant current charging.  But since the piezo is relatively low power, using the BQ25570 to directly charge the battery is likely okay.

    can you provide more info (vendor, part number, rectification method, etc) for the piezo device?  We are currently spec'ing a new BQ255xx device and I would like more info on input sources.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Genius 3365 points

    Hi Sir,

    They used the ADI/ LTC3588-1 and the bridge rectification for the piezo device.

    BTW. the vout of piezo device is 20V, so the vin of BQ25570 can not meet their required, please also advise the suitable device. Thanks!

  • +1 in reply to Henry Wang3
    TI__Guru**** 167146 points

    Hi Henry,

    The best option is BQ25570 with a zener diode clamp to 5.5V on VIN_DC however the clamp will steal current from Piezo so may not be practical. I do not see any other suitable device the BMS portfolio. 

    Regards,
    Jeff

  • 0 in reply to Jeff F
    Genius 3365 points

    Hi Sir,

    Thank you so much for responding.