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Original question:

BQ24610: STAT1/STAT2 OFF/OFF meanings in documentation

BQ24610: System restart

Jeff Xie
Intellectual 1780 points
Part Number: BQ24610

Hi all,

According to the datasheets, the input power must be at least 0.5V higher than the battery voltage. Our battery voltage is 16.8V when fully charged, and the input power is 19V.

However, there is a high-power device in our instrument that will cause the power supply to drop during operation (the voltage waveform is as shown below) As shown, it drops to about 16V instantaneously, and the duration is short). Will this drop affect the system power (BQ24610 works abnormally, the system loses power, etc.)?

  • 0
    TI__Mastermind 24075 points

    Hi Jeff,

       There are 2 loops internal to BQ24610 that could come into play here (see bullets), that also depend on if you have a BATFET (PFET driven by BATDRV in between battery and system). This will also depend on if the high powered device is hanging off the input rail, or if it is connected at the system rail.

    1. Input current regulation loop (based off of sense resistor value between ACP and ACN, as well as voltage on ACSET)
    2. SLEEP mode (based off of VCC sensed by IC, and battery voltage sensed at SRN)

    Can you clarify how the overall system is set up?

  • 0 in reply to Kedar Manishankar
    TI__Intellectual 1780 points

    Hi Kedar,

    The high powered device is hanging off the system rail after one boost chip to 24V.

  • 0 in reply to Jeff Xie
    TI__Mastermind 24075 points

    Hi Jeff,

        BQ24610 will prioritize system load, if input current required to supply both system load and charge current, exceeds the input current limit setting. Input current regulation loop is active when sensed current across sense resistor between ACP and ACN reaches the setting from Equation 3. of datasheet.

    One item to check is whether your input supply can supply solely your system, without crashing. (do not consider charge current.) If it can, then there is no issue, as when the system load requires power, the input supply can provide both charge current and system load, and if system + charge current exceed input current setting, then charge current will be reduced to prioritize system load.

    However BQ24610 is not designed for applications where system load exceeds the input supply power capabilities. This is because input voltage will sag to maintain system load power, and this will cause charger to possibly hit SLEEP threshold (SLEEP depends on delta between VCC and SRN). When SLEEP is hit, converter is disabled, ACDRV is pulled to VCC turning off input reverse blocking FET, and BATDRV is pulled to VCC - REGN, which turns on the BATFET and battery will begin to supply system load. This will cause oscillation between SLEEP and normal operation, as VCC voltage will climb back up once load on input supply is removed (in this case will occur when SLEEP is hit). Once it satisfies SLEEP rising, then converter will turn back on and you will have this oscillation of input crashing, as well as battery charging and discharging to supply system load.