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TPS65150-Q1: TPS65150-Q1 change output voltage was set by resistors, but output was wrong.

Part Number: TPS65150-Q1
Other Parts Discussed in Thread: TPS65150

Dear,


our client use TPS65150-Q1, but we find the if  R209 29.4k ohm change to 39.2 ,VDDA output voltage is 3V ,not 9V.


but we just change R209 39.2k ohm to 29.4K ohm, output voltage is 12v, it`s right.

why we change R209 29.4K ohm to .39.2k ohm  output is 3v?

if any suggestion, Please advise me.


Thanks,


Best regards,


Lawrence.

schematic as below:

DC-DC TPS65150 (3).pdf

  • Hi,

    I have notified our expert regarding this issue. Please expect a response by 8/20/18

    Regards,
    Aaron
  • Hello Lawrence,

    Boost output voltage calculation based on your schematics should be as follows:
    VDDA0 = 1.146 * (1+(R202+R205)/R209).
    So with R209=29.4K, VDDA0 should be ~12.4V.
    And with R209=39.2K, VDDA0 should be ~9.6V

    Are you not measuring these voltages based on the values of R209?
    I am not sure if I fully understand what you are describing. Can you please clarify?
    Kind Regards,
    Liaqat
  • Hello Liaqat Khan,

    The actual measurement voltage waveform is as follows, the orange waveform is 12.4V (R209=29.4K), and the green waveform is 9.6V (R209=39.2K).

    if any suggestion, Please advise me.

    Thanks,

    Best regards,

    Chi Wei Chang.

  • Hello,

    It seems that boost is shutting down when the voltage is set to lower 9.49V. Likely reason for boost shutting down is that at lower boost output voltage (9.49V), VGH may not be able to achieve regulation. Boost output voltage is an input supply voltage for positive and negative charge pumps and if VGH/VGL do not achieve regulation within the time delay set by FDLY, the device shuts down. You can verify that by removing C201 and placing a zero ohm resistor in its place to short FDLY pin to VIN2 net and see if boost does not shutdown anymore.

    Kind Regards,

    Liaqat

     

  • Hello Liaqat Khan

    The C201 has been removed and a zero ohm resistor is placed. The VDDA0 voltage is 9.6V, but the VGH and VCOM voltages are 0V.

    if any suggestion, Please advise me.

    Thanks,

    Best regards,

    Chi Wei Chang.

  • Hello Chi Wei,
    I am not totally sure what is causing the VGH/VCOM to not come up. Is VGL coming up with proper voltage?
    I reviewed your schematics once more and have following comments:
    - R220 is recommended in the datasheet to be between 39K and 150K ohms so as not to load the REF. Can you please change this resistor to 150K and adjust R214/R216 accordingly?
    - Similarly, can you please change R221 to 56K and adjust R215/R217 accordingly?
    - I noticed that pin 19 GND connection of TPS65150 in your schematics is not showing a junction dot to show a proper connection to GND. Can you please double check in your layout if pin 19 is properly connected to GND?
    - Finally, you seem to have two separate ground nets connected to each other through R207. I am thinking that if the two grounds are not connected appropriately, they can cause issues with device operation. Why did you employ two separate ground nets in your design? Datasheet schematic examples only show one ground connection throughout. Can you please experiment with connecting these two grounds at various points on the board to see if this improves the behavior?

    I hope that one of these suggestions resolves you issues.
    Kind Regards,
    Liaqat
  • Hello,
    Since I have not heard from you in a while, I am going to close this thread. Please feel free to open another thread if there are further questions.
    Kind Regards,
    Liaqat