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BQ40Z60: BQ40z60 charge current and system load

1671828
Prodigy 160 points
Part Number: BQ40Z60

Hello,

I was initially under the impression that charging on the BQ40z60 operated like this:

- Charger output current is limited based on voltage on HSRP/HSRN

- Pack sense resistor provides charging current feedback and, in the absence of a system load, the charger output will be reduced to meet the target charging current.

- System can draw current up to the charger output current limit minus the charge current without impacting charge current. Any current in excess would reduce charge current.

However, it seems that instead it operates like this:

- Charger output during charging is limited to ChargingCurrent(). If there is a system load, it will ALWAYS reduce the actual battery charge current.

- When the battery is NOT charging, the current will be limited to the setting in Max Current Register (sluua04c page 57). This could be higher or lower than ChargingCurrent().

Can you please confirm what the intended operation looks like? If it is supposed to be the latter - why?

  • 0
    Prodigy 160 points
    And to add to this ostensibly the value of the "Max Current Register" is to provide some input current limiting capability to protect the AC adapter. But the "Max Current Register" is ONLY relevant when not charging. If the charge current setting is higher than the "Max Current Register" setting, it will still pull that much. So I really don't get what the point of it is.

    I may be slightly ticked off that this part doesn't implement the "Power Path" management that many of the dedicated charging chips do :).