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TPS650860 Max output current

Colin Hankins
Intellectual 570 points
Other Parts Discussed in Thread: CSD87381P, CSD87588N
What is the maximum allowed output current through the external FETs on Buck1 and Buck2? Or is it whatever the external FETs can handle as long as Rlim is appropriately set?

Where can I find the estimated efficiency?

Thanks, 
Colin
  • 0
    TI__Genius 16870 points
    Colin,

    The external FET rails can go up to whatever the external components allow for. Typically, application requirements and FET options with the TPS65086x driver limit the max current in the range of +20A. You can go higher but some tradeoffs will need to be made. Can you tell me the max current you are thinking of?

    The efficiencies can be found in the user's guide for the Remote Radio Head and the datasheet of the TPS650860.
  • 0 in reply to Michael Green
    Intellectual 570 points
    Thank you Michael.

    We have a couple of applications and the highest output currents would range from 10A to 20A. Our highest requirement, at the moment, is 10A on one rail and 20A on the other.
  • 0 in reply to Colin Hankins
    TI__Genius 17380 points

    Hi Colin,

    On the EVM there are two FETs, the CSD87381P for BUCK1 and BUCK6 and the CSD87588N for BUCK2. The CSD87381P's have been tested with 1V out up to 11A and the CSD87588N has been tested with 1V out up to 21A. I've attached the efficiency measurements for the BUCK2 up to 20A for both the EVM BOM, and a more performance optimized, larger BOM with larger FET/inductor for your information.

    Note that the main limiting factor will be the power dissipation in the FETs. If you are using higher than 1V output, say 3.3V, then the maximum current allowed decreases as the power output increases. For reference, during my testing for 3.3V output on BUCK2 with the CSD87588N, I was blowing my FET around 18.5A output with 21V input. This is worst case as far as efficiency so we see high power dissipation in the FET.