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BQ24618: About full charge detection

imai akio
Prodigy 10 points
Part Number: BQ24618
Other Parts Discussed in Thread: BQ24617, BQ24610

BQ24618に入力24V/2.1AのACアダプタを使用する充電回路基板を設計していますが、フル充電検出電圧を23.86に設定すると、フル充電検出電圧付近で充電が停止します。
充電電圧を23.37Vに設定し、バッテリを23.56Vに充電すると、瞬時に停電が発生し、電圧が23.35Vに低下し、CVモードで充電が再開されます。
原因究明の方法を教えてください。

  • 0
    TI__Mastermind 34495 points

    Hello,

    Can you please repost your question in English? Your translation is greatly appreciated.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 10 points

    I am designing a charging circuit board that uses an AC adapter with an input of 24V/2.1A for the BQ24618, but if I set the full charge detection voltage to 23.86, charging stops near the full charge detection voltage.
    When the charging voltage is set to 23.37V, the battery is charged to 23.56V, then an instantaneous power failure occurs, the voltage drops to 23.35V, and charging is resumed in CV mode.
    Could you tell me how to investigate the cause?

  • 0 in reply to imai akio
    TI__Mastermind 34495 points

    Hello,

    The BQ24618 is a buck charger. You need headroom between the input voltage and the full charge voltage. Please see Section 10 Power Supply Recommendations: "For proper operation of bq2461x, VCC must be from 5 V to 28 V (bq24610) or 24 V (bq24617). To begin charging, VCC must be higher than SRN by at least 500 mV (otherwise, the device will be in sleep mode). TI recommends an input voltage of at least 1.5 V to 2 V higher than the battery voltage, taking into consideration the DC losses in the high-side FET (Rdson), inductor (DCR), and input sense resistor (between ACP and ACN), the body diode drop of RBFET between VCC and input power supply, and battery sense resistor (between SRP and SRN). Power limit for the input supply must be greater than the max power required by either the system load or for battery charging (the greater of the two)."

    Either the regulation voltage needs to be lowered or the input needs to be increased.

    Regards,

    Mike Emanuel