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BQ24640: When is supercap fully charged?

Dave Nadler
Intellectual 365 points
Part Number: BQ24640
Other Parts Discussed in Thread: TLV840

Hi - I'm trying to finish a bq24640 design but...

The datasheet table 2 says STAT goes on (OC low) when CE is high and blinks on fault condition or CE off.
Figure 7 shows STAT goes low and stays low (after initial glitch at turn-on).

However, what I (and most folks using supercap for ride-through) need is to know when supercap is charged,
as it must be fully charged before I can start IO activity that requires ride-through (ie writing to flash).
How do I determine supercap is fully charged?

Thanks!
Best Regards, Dave

  • 0
    TI__Guru*** 147925 points

    Hi Dave,

    The super cap charger doesn't really terminate and stays in CV mode to constantly top off the super cap.  To know when the cap is charged, you could use an MCU ADC or SVS like TLV840 to monitor the FB pin voltage.  When V(FB)=2.1V, the supercap is charged.

    Regards,

    Jeff