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BQ25798: Safty timer and MPPT question

PYTsai
Genius 11880 points
Part Number: BQ25798
Other Parts Discussed in Thread: TPS2120

Hi 

My customer got some questions can you help 

  1. There are safety timers for trickle charge, pre-charge, and fast charge modes. What will happen if the safety timer expires? Will the charger attempt to charge the battery again?
  2. Can keep turn on the MPPT if the input source is not from solar panel but from adaptor ?
  3. Is there anything suggest application note regarding BQ25798 MPPT design consideration that we can refer to (so we can avoid mistake using MPPT)?  

Thanks!

PY Tsai

  • 0
    Prodigy 10 points

    Hi 

    Additionally, regarding item 2: if the MPPT feature is enabled but the input source comes from the power mux (TPS2120) output (and the power mux input is connected to a solar panel), will the MPPT feature still work?

  • 0 in reply to Godfrey Chen
    TI__Guru**** 169256 points

    HI Godfrey and PY Tsai,

    Regarding 1, if those timers expire and the battery voltage stays constant, charge is suspended.  However, if the battery voltage crosses a charge state threshold voltage (e.g. battery drops below VSHORT after precharge current stops) after timer expiration, charger automatically restarts charge in the new state instead of requiring input POR, /CE pin toggle or host interaction for restart.

    Regarding 2, MPPT can be turned on at any time, attached to any source.  EN_MPPT bit resets to 0 if the battery voltage drops below the SYSMIN voltage.

    Regarding 3, yes.  Please read https://www.ti.com/lit/pdf/sluab26. 

    Regards,
    Jeff