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Hi,
My current design is using BQ25505, but the datasheet does not state MUX signal if primary battery is not connected. Will VSTOR keep internal reference to the secondary battery level even if it is lower than the VBAT_OK_PROG when Primary battery is detached? Thank you.
Regards,
Diana
Hi Diana,
No. There is a PFET that connects VSTOR=VBAT_SEC. If there isn't enough power at VIN_DC to drive the load at VSTOR and charge the battery at VBAT_SEC, both VSTOR and VBAT_SEC voltages fall. VBAT_OK is the output of comparator monitoring VSTOR voltage and has no effect on charging.
Regards,
Jeff
Diana,
VBAT_OK is the output of comparator that reports where the VSTOR=VBAT_SEC in relation to the VBAT_OK_PROG and HYS resistors. It does not affect the operation of the converter. The MUX is powered by a diode OR of VBAT_SEC and VBAT_PRI. As long as VBAT_SEC is up, the MUX is powered.
Regards,
Jeff