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BQ24650: disabling charging

Olrik Maier
Expert 5020 points
Part Number: BQ24650

Hi Battery Chargers Team,

I cannot really see the difference between the Termination Enable and MPPSET pins. Both can disable the charging? What is the main difference if it is any?

 

  • That is clear pulling down MPPTSET pin < 75mV (GND) to stop charge
  • But it is not clear how Term EN  works
  • Is it possible to use 5Vdc to TE pin or 3.3V the max?

 

  • Once I would like to use a chip enable e.g. from SCM circuit can I use both or rather MPPT pin?

 

  • I think VFB AD is 8 bit resolution. Am I right?

 

  • On the EVM board the V in is direct contact with load(system output) – using not a power source unit but real solar panel that would break , not to load the charger circuit but only the battery pack.
  • How the chip handle the charge under battery is loaded? Is it stop or we need to disable the charging?

 

  • What do you think to put a buck boost converter to the Vin to stabilise the input voltage level? Since solar panels voltage can be low in case of low irradiation

Best wishes,

Olrik

  • 0
    TI__Guru**** 166156 points
    Olrik,

    Pulling MPPSET low disables the buck converter completely regardless of charge current. TERM_EN stops charging only when the battery is almost charged and the charge current has dropped to 1/10 of the charge current set point. Therefore, please use MPPTSET low to disable the charger.

    This IC's buck converter is all analog, including the VFB pin. There is no AD converter.

    If the system is loading the solar panel, the charger will attempt to charge until the MPPSET voltage senses that the output of the solar panel has dropped to the MPP set point.

    Most dc/dc converters, buck-boost included, are designed to be powered by a low impedance power source and so pull up to their maximum input current. This usually results in collapsing the output of the HiZ solar panel, unless the converter's maximum input current is below the solar panel's MPP output current capability. That is why when powered by a solar panel, the converter/charger needs a MPPT feature. Any of TI's charger's with VINDPM (called MPPSET for the bq24650) can be used to prevent crashing the solar panel output.