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TPS92691 buck boost current sensing

David Park
Expert 5400 points

Hi,

At buck-boost typical application in the datasheet, current sensing resistor is placed at LED-.

in case of other topology, it is placed at LED+.

I think it seems to be because current direction is opposite at buck-boost.

Because absolute maximum is enough, it is no problem that sensing resistor is placed at LED+.

Am I correct?

Can I place sensing resistor at LED+?

Thanks.

  • 0
    TI__Expert 3885 points
    Hi David,

    Putting current sensing resistor at LED- in buck-boost topology is because both CSP/CSN pins will see voltage around input voltage level.
    It is ok if you put it on LED+. The limitation of CSP/CSN abs max at 65 V imposed and you have to make sure that LED+ must be lower than 65 V w.r.t. ground.

    Hope the above helps.
  • 0 in reply to Issac Hsu
    TI__Expert 5400 points
    Issac,

    LED+ voltage will be Vin+VLED.
    Therefore Vin+VLED has to be below 65V.
    Am I correct?

    Schottky is place to different place from usual buck-boost.
    Is there specific reason?

    Thanks.
  • 0 in reply to David Park
    TI__Expert 3885 points
    Hi David,

    You are correct. VIN+VLED has to be below 65 V.

    This buck-boost configuration is in fact a boost w.r.t. ground while we place the load between output voltage and battery (or input).
    Hence, it is also called boost-into-battery (input) type configuration.

    Thanks.