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Power solution recommendation

Yang Wu
Intellectual 2830 points
Other Parts Discussed in Thread: TPS7A91

Hi Team,

My customer has an issue that SMPS has 100mV ripple @5V 1A output. while the load is strict with the power (much lower ripple). my question is that does TI has DC/DC solution with same input and output? 

my current solution for the customer is to increase the output of the former SMPS and then use a LDO to get a much quieter power for the load. it's OK? 

thanks a lot.

Yang

  • 0
    TI__Genius 14317 points
    Hello Yang,

    Are you looking for a buck DC-DC converter? Please provide the input and output requirements including ripple and noise requirements.
  • 0 in reply to Jeffery Pfarr
    TI__Intellectual 2830 points
    Hello Jeffery,

    Actually it's not Buck/Boost, customer wants 5V input (with 100mV ripple) and 5V output (with lower ripple, perhaps 30mV), which means the convert doesn't step-up/step-down the voltage, just has filter function to get rid of some ripple. so, do we have solutions?

    I recommend the customer to add a LDO.

    Thanks.
    Yang
  • 0 in reply to Yang Wu
    TI__Guru 55940 points
    Hi Yang,

    Unfortunately the PSRR for an LDO is negligible when in dropout because the pass element will be driven as hard as possible in an attempt to bring the output voltage into regulation. As a result the LDO output will follow the input much in the same way as a resistor. Are you able to increase your input voltage so that we can take advantage of the LDO PSRR? A high PSRR LDO such as TPS7A91 would only require an input voltage of 5.2 V in order to regulate the output voltage at 5 V.

    If you are not able to raise your input voltage, a passive LC filter is likely your best option.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    TI__Intellectual 2830 points

    Hi Ryan,

    Thanks for your reply. while the customer couldn't increase the input voltage because the former power board is an universal board.

    Now the solution is using TPS63030 (buck-boost) as the latter DC/DC to get 5V output with lower ripple.