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BQ25622: Questions about BQ25622 application

Will Wang47
Expert 6970 points
Part Number: BQ25622

Hi team,

My customer would like to use BQ25622 as a power mux function in their application. Block diagram as following shows:

They get a battery and Vbus, their system is at Vsys. They get following questions:

1. If there is no battery, they would get power from the Vbus in normal mode; however, in this case, if they put the part into HIZ mode by write EN_HIZ bit, there will be no output at Vsys, right?

2. If there is a load at Vsys, Vbus is plugged in to support this load and charge the battery, when remove VBUS, what's the response time switch to VBAT? And how to calculate the dip during the switch time?

Could you help comment on those 2 questions?

Thanks and Best Regards,

Will

  • 0
    TI__Mastermind 37105 points

    Hi Will,

    1. In HIZ mode, "RBFET (Q1), HSFET (Q2) and LSFET (Q3) are turned off. The RBFET and HSFET block current flow to and from VBUS, putting the VBUS pin into a high impedance state. The BATFET (Q4) is turned on to connect the BAT to SYS. During high impedance mode, REGN is disabled and the digital clock is slowed to conserve power." With no battery there would be no regulated voltage on SYS.

    2. It all depends on how much SYS capacitance you have. When VBUS is removed the SYS load will try to maintain and it will start to drain the SYS cap. When the SYS voltage falls below the BAT voltage, supplement mode will automatically start. I = C*dV/dt would be a good starting place (assuming a constant current draw).

    Regards,

    Mike Emanuel