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BQ25172: ISET pin voltage for changing charging current

Koshi Ninomiya
Expert 4690 points
Part Number: BQ25172

Tool/software:

Dear Team,

My customer is evaluating the BQ25172EVM to charge 1-cell NiMH batery (1.2V, I_charge: 500mA). When it is initial charge, the charging current need to be change at V_bat=1.1V. So, the charging current setting need to be changed by monitoring the battery voltage.

Q1: ISET pin has a external RISET. If a MCU DAC output (< V_ISET) is connected to ISET pin through a series resistor, can the charging current be changed?

Q2: What is ISET pin voltage?

Best Regards,

Koshi Ninomiya

  • +1
    TI__Guru 71346 points

    Hi Koshi

    Koshi Ninomiya said:
    Q1: ISET pin has a external RISET. If a MCU DAC output (< V_ISET) is connected to ISET pin through a series resistor, can the charging current be changed?

    Sorry but this would not work,  The ISET pin needs a resistor to ground, applying a voltage will not work.  But if the MCU is used to control a mosfet that will switch in or out a resistor the current can be changed.  This could be a high or low setting, see below pdf.

    Koshi Ninomiya said:
    Q2: What is ISET pin voltage?

    When in current regulation the voltage is 1V.

    2148.Dual charge current -bq2517x.pdf