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TIDA-03029: Where to connect load on BQ25890H

Michele Santucci
Intellectual 675 points
Part Number: TIDA-03029
Other Parts Discussed in Thread: BQ25890H,

Looking for application notes on BQ25890H I stumbled on TIDA-03029. From schematics it's quite clear

that MSP430F5529IP unit is fed (trough TPS70930DBVR) by VBUS or BAT and not from SYS output of

the BQ25890H as I was expecting.

There's probably an underneath logic but I seem unable to discern it.

Why micro is not fed from SYS? It's a recomended solution i.e. TI suggest to apply actual loads with a similar strategy?

What's the need for SYS output then?

The USB connection from MSPxxx (J4) can be shared with main USB connection (J1) or power managment handshaking

will interfere with USB communication?

  • 0
    TI__Guru 59531 points

    Hi,

    Referring to 8.2.3 Device Power Up from Input Source, when plugging in an adaptor, the converter will power up (i.e. ramp up SYS) after the input source type detection. In the TIDA-03029 reference design, the MSP430 may control D+/D- lines before the converter powers up when SYS is not available.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Intellectual 675 points

    The negotiation over D+/D- lines MUST be done in order to have SYS available or can be done after that?

    It looks like that if I don't negotiate some optimized feature BQ2890 stars with a 'standard' setup (if safety rules apply). Right?

    Can I re-negotiate the optimized features after the 'standard' setup took place? It looks like is possible setting FORCE_DPDM.. Right?

  • 0 in reply to Michele Santucci
    TI__Guru 59531 points

    Hi,

    The power up sequence from input source is fixed.

    D+/D- driver function is optional. 8.2.3.3.1 D+/D– Detection Sets Input Current Limit on the d/s describes "standard" D+/D- detection the device may do without using D+/D- driver.

    Please refer to 8.2.3.3.2 Force Input Current Limit Detection on the d/s for force D+/D- detection function.

    Thanks,

    Ning