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tps65145 power test

xf He
Prodigy 100 points
Other Parts Discussed in Thread: TPS65145

tps65145 power test :

Not mount DMD,The power test value is VOFF 6.6V/ VRST-7.8V/VIBAS 13.73。

Do I need to mount DMD  to confirm power test for tps645?

thanks.

  • 0 in reply to xf He
    TI__Mastermind 18550 points

    Hello,

    If I understand your question correctly, you are asking if you need to connect load to the TPS65145 output rails to test proper powerup of TPS65145. If so, I do suggest to connect the load to to ensure that all rails power up correctly in your target application.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Prodigy 100 points

    thank you !

     Yes, your understanding is correct.

    There is no connection load, I test the output voltage value is not correct。

    I'd like to know if the chip is working OK and whether it needs connection load test.

    I'll take your advice to connect load test  the accuracy of the output voltage，Thank you very much！

  • 0 in reply to Liaqat Khan
    Prodigy 100 points

    hello ， 

    connect load test，The output voltage is still wrong。

    I change R19 resistance value to 430KΩ, output voltage value is 3.3V。

    I change R19 resistance value to 120KΩ, output voltage value is 3.3V。

    Change to the original value（360KΩ） again, output voltage value is 6.6V。

    Please help me about this ，thank you !

    Best regards,
    hexf

  • 0 in reply to xf He
    TI__Mastermind 18550 points

    Hello,

    I believe all other voltage rails are incorrect because boost voltage is not at correct level. Schematically, the only thing I can think of is that perhaps some instability because of high 22uH inductor value. Typical schematics recommendation in the datasheet is for 4.2uH boost inductor. Can you please capture Vin, SW node and boost output voltage on same scope plot? Not sure but this may provide some clues as to why you are not getting correct voltage at boost output.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Prodigy 100 points

    hello,

    The waveform is as follows，1 CH boost output  ; 2 CH  SW; 3CH  VIN 3.3V 

    1 CH   boost output ; 2CH SW

  • 0 in reply to xf He
    TI__Mastermind 18550 points

    Hello,

    I don't see any particular problem with the waveforms so I am not sure why you are not getting the correct voltage level at the boost output. You may want to have your local TI FAE check your board in the lab to further debug this.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Prodigy 100 points

    Hello,

    I found that the Internal reference output voltage of pin 20（REF） is 0.826V。What is the cause of the reference voltage error？

  • 0 in reply to xf He
    TI__Mastermind 18550 points

    Internal reference is supposed to be at 1.213V nominal. The only thing that I can think of that can cause it to be this low is perhaps negative charge pump feedback network but with R26 at 75K, this should not load the reference. So I would suspect a damaged device. Is this just one board or do you have more than one board with this reference voltage issue?

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Prodigy 100 points

    hello，

    The reference pin (REF) in my schematic diagram lacks a capacitor. I add a 0.22uf capacitor on the board, and the output voltage is normal。

    Reference pin(REF) is the output type, Why does the capacitance affect the voltage so much？

    thank you！

  • 0 in reply to xf He
    TI__Mastermind 18550 points

    I am glad that you found the missing capacitor and I somehow overlooked it when reviewing your schematics. I do not know the details of the internal circuit but this capacitor is required for proper operation of internal reference circuit.

    Kind Regards,

    Liaqat