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BQ25700A: Could BQ25700 be a pure buck boost controller?

Part Number: BQ25700A
Other Parts Discussed in Thread: BQ25700

HI Support team member

Could BQ25700 be a pure buck boost controller? That is, we didn't use its any charger function, we just make it be a buck boost controller IC.

If it can, how could I draw its schematic? Is there reference design?

thank you~!

  • Jeffic,

    Unfortunately there is no reference for this. This is possible, but there are a few things to consider.

    The VSYS pin provides a regulated output set by the minimum system voltage (VSYSMIN) regulation setting on REG0x3E[13:8]. As long as sufficient power is provided through either VBUS or VBAT, VSYS will maintain this node above the minimum voltage. 

    However, if there is a battery connected to VBAT that is greater than your minimum voltage setting, then the BATFET will fully turn on and short VSYS to VBAT with a minor VDS voltage drop across the BATFET. 

    In the overvoltage condition, SYSOVP will latch off the converter. SYSOVP is configured by the CELL_BATPRESZ pin resistor network. Upon converter start up the pin voltage is compared with respect to VDDA to set an appropriate battery voltage and SYSOVP value according to table 1. This latch condition can be reset by replugging the adaptor or by setting the SYSOVP bit to 0.

    With a battery connected VSYS can vary anywhere from VSYSMIN to SYSOVP. If this variation is too great for your application, then you will need post regulation between VSYS and your system load from an LDO or switching converter.

    I strongly recommend using a post regulation solution between VSYS and VSYSMIN.

    References 8.4.1.1, 8.6.5, 8.3.2.3

    Thanks,

    Ricardo