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Low efficiency observe at TPS542941

Eng Lih Khaw
Expert 2000 points
Other Parts Discussed in Thread: TPS542941

Hi,

Customer of mine is evaluating TPS542941PWPR and observe very low efficiency

Below is customer testing condition:

Voltage input: 12V

Output CH1: 1.3V

Output CH2: 1V

Efficiency: ~40%

 

As shown in the above diagram, there’s an inductor before the Vin pin. Low efficiency was observed when measuring near to the Vin pin of TPS542941. Below are my questions:

  1. Why there’s so much different in  efficiency measuring at different point? Could this be caused by huge current drop after the inductor?
  2. At which point should customer measure the input power?

Thanks

  • 0
    TI__Guru**** 191445 points

    There will be some losses in the inductor.  I would expect the efficiency to be higher at the IC.  It all depends on what your customer is interested in efficiency wise.  If it were me I would be interested in the total loss.  One thing you need to be sure of...you will need a bulk capacitor between the inductor and the IC in addition to the ceramic bypass required.  I would suggest starting with 100 uF.