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TPS54226 - About change the output voltage by the external DAC

Guru 21045 points
Other Parts Discussed in Thread: TPS54226

Hi Team,

 

Our customer would like to know whether TPS54226 can change the output voltage by the external DAC.

I understand that this method is common for current mode DC-DC.

So, can I use this method to DCAP2 DC-DC?

Could you please let us know if you have any concern?


 

Regards,

Kanemaru

  • Hi Kanemaru,

    Yes, it is fine to use an external DCA to regulate the output voltage. D-CAP mode and current mode both use the voltage feedback to compare with an internal reference voltage. The difference is that D-CAP mode use a comparator to compare these two voltage level and current mode use an error amplifier to compare these two voltage level. The impact of the DCA will be the same.

    Best regards,

    Anthony Lang

  • Hi Anthony-san,

    Thank you for your response.

    I understand. Thank you very much.

    Regards,

    Kanemaru

  • Hi Anthony-san,

     

    Thank you always for your kind support.

    I have one more question.

     

    [Question]

    Our customer would like to start up TPS54226 at the following sequence.

    Could you please let us know if you have any concern?


     

    Regards,

    Kanemaru

  • Hi Kanemaru-san,

    I do not see any problem here. Only one thing that will happen during the time gap before EN pin is powered on and after DAC is powered on. DAC will charge the output cap thru the feedback resistor network with a very small current. If the time gap is too long, there will charge on the output cap and there will be a fake voltage on output cap before EN is powered on. When EN is pulled high, the converter will soft start and this fake voltage will gone and the output voltage will go to the nominal output voltage the DAC set. The output impedance of the DAC and the voltage feedback resistor divider will need to be carefully selected to let the DAC control the output voltage level.

    Best regards,
    Anthony
  • Hi Anthony-san,

    Thank you for your prompt reply.

    I understand. Thank you very much.

    Regards,

    Kanemaru