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BQ25758: two or more controllers parallel

Sybren Bos
Prodigy 80 points
Part Number: BQ25758
Other Parts Discussed in Thread: BQ25756

Tool/software:

to control the output voltage of the product we are develloping more accurately we want to sense the output voltage before the shuntresistors instead of after. 

this will hopefully minimise the effect of the voltage sense inaccuracy by isolating the two sense points by the resistors.

will this cause any problems for the controller?

also do you have anymore tips on how to wire multiple cirucits in parallel?

  • 0
    TI__Expert 5695 points

    Hi,

    Wiring two controllers in parallel is usually only recommended for when both controllers are in the constant current mode. Will this be the case? Can you draw a block diagram for this and explain the use case?

    Best,
    Michael

  • 0 in reply to Michael Bradbourne
    Prodigy 80 points

    they will be used for a universal solar mppt and will indeed be in cc mode most of the time except for when the battery is almost full and the device needs to go in cv mode. 

  • 0 in reply to Sybren Bos
    TI__Expert 5695 points

    Hi Sybren,

    The BQ25758 is not a battery charger and does not have MPPT. Are you referring to the BQ25756?

    Best regards,
    Michael Bradbourne

  • 0 in reply to Michael Bradbourne
    Prodigy 80 points

    no, we are using the bq25758 because the solar charger is supposed to universal for battery voltages and types so the bq25756 is suboptimal for our application. we will use a mppt algorithm on a microcontroller and control the input current limit based on the mppt calculations

  • +1 in reply to Sybren Bos
    TI__Expert 5695 points

    Hi Sybren,

    Thanks for the clarification. When using the BQ25756 to charge a battery in parallel, the recommended condition we use is to set the regulation voltage on one device lower than the other device so that you have a clean termination on each device. I will recommend the same thing for the BQ25758. The BQ25758 will not terminate, but if the output voltage goes above the regulation point, it will stop switching which will have the same effect as termination. This will avoid the two devices attempting to be CV sources at the same time.

    Best regards,
    Michael Bradbourne