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TPS92510 Vin 5V application?

Chen Bogey8
Mastermind 9990 points
Other Parts Discussed in Thread: TPS92510

Hi Sir 

We design TPS92510 in 5Vin and Vout set to 3.6V, output current set to 0.24A. 

But we find we need increase Vin to 5.4V, then LED can normal work.

1.When Vin = 5.4V, to measure LED Vf = 2.75V.

2.when Vin =5V, to measure LED Vf = 2.39V. Can't be drived.

3.When Vin <5V, the Led vf will decrease depend on Vin.

From spec, the TPS92510 should be work in Vin=5V and Vout 3.6V/0.24A. may our design have something wrong to case this kind issue? 

LXCL-EY17.pdf

  • 0
    TI__Mastermind 25500 points
    Are you not using an output capacitor? If not this device requires an output capacitor for two reasons: The first is that it is current mode control and it may not be stable without one. The second is that BOOT will supply current through C45 trying to charge the capacitor. If you have an output cap the output voltage stays low since the cap will absorb this current while it charges. If there isn't a cap the charging current will go through the LED and bring up the output voltage and the PH node will be at the same voltage as the LED. That is why you need to turn the input voltage up to start, you need to charge C45 up past its UVLO threshold.