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BQ32000: Backup Supply Current - Test Condition

D_Bartlett
Prodigy 670 points

Part Number: BQ32000

Hi Team,

I have a question about one of the test conditions listed on the BQ32000 RTC for IBACK.

What exactly is meant by "Vcc needs a pulse"? Does this have any impact on a design or just a piece of test minutae?

Also, what is the forward voltage of the diode in the trickle charger circuit?

Thanks

  • 0
    TI__Expert 4650 points
    Hi Dylan,

    Apologize for the delay. Section 8.2.2.3 of the datasheet outlines a specific startup condition for the backup supply to meet the IBACK specification. The basic idea is that VCC must be briefly powered on after a full power loss situation.

    If VCC were to drop out and the VBACK supply later drops out as well, the device enters a full power loss. When coming back from this full power loss, the VCC pin needs to be pulsed before VBACK and can take over as the main supply with the specified IBACK current.

    Will ask design about this diode forward voltage.
  • 0 in reply to Phil Beard
    TI__Prodigy 670 points
    Hi Phil,

    Thanks for clearing this up, it makes more sense now.

    Did you manage to get an answer from the design team? I am assuming that the forward voltage is something like a standard 0.7V as with most diodes?

    Dylan