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TPS61165: Current Issue

Errol Leon6
Expert 5850 points
Part Number: TPS61165

Hello,

My customer is using TPS61165 to drive a string of LEDs and is finding they are unable to drive no more than ~140 mA. The part is rated at 1.2 A, and by back of the envelope calculations should be 26.6*.14/5/.85 = .88 A,. 

This is with the expected output voltage of 26.6V, current in at 5V, with a conservative 85% efficiency,

Is there something with the device possibly limiting the current at this level? 

Thank you!

Errol Leon

Texas Instruments

Field Application Engineer

  • 0
    TI__Mastermind 22745 points
    Hi Errol,
    You mean you want to limit the current at 0.88A? If my understanding is right, 0.88A is the average input current, considering the current ripple on inductor, the peak current should be larger than 0.88A. If you want to limit the current ripple to a small value, you need to choose higher inductor value. Thanks.
    Sean
  • 0 in reply to Sean Zhou
    TI__Expert 5850 points
    Hello Sean,
    The 0.88A is the expected output current based off an output voltage of 26.6V, input at 5V, with an 85% efficiency. However, the customer only sees 140mA of output current; which the customer is expecting 0.88A. Is it correct that based off the calculation (in the prior post) that the customer should see 0.88A? or is there something not being accounted for?

    Thank you for your support!
    Errol
  • 0 in reply to Errol Leon6
    TI__Mastermind 22745 points
    Hi Errol,
    No, you use this equation to calculate the average input current, not output current, you have set the expected current to 140mA. So you should only see 140mA. TPS61165 can not support 0.88A output current with Vin=5V, Vout=26.6V. Did I explain clearly? Thanks.
    Sean