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Need suggestion on the Bulk capacitance used on TPS5430 design

Bhupendar Singh
Prodigy 100 points
Other Parts Discussed in Thread: TPS5430

Hi,

we are using 3 TPS5430 in our design to generate 12V@0.5A, 5V@0.5A and 3.3V@1A .

As per the design we got from SwitcherPro it is suggested to use tantalum capacitor of value 100uF,120uF and a20uF respectively at output of each of power supply as Bulk capacitor.

We want to avoid using Tanatalum or electrolytic in our design hence wanted to confirm if it is ok to use 10uF 25V ceramic capacitor (C3216X5R1E106K)  for 12 V rail inplace of 100uF tentalum, 22uF 6.3V ceramic capacitor (C1206C226K9PACTU) for 5 V rail inplace of 120uF tentalum, and 100uF,6.3V ceramic capacitor (C1206C107M9PACTU) for 3.3 V rail inplace of 100uF tentalum. Will the power supply be stable with these lower value of capacitances.

 

Thanks & Regards,

Bhupendar

  • 0
    TI__Guru**** 191445 points

    In general, the TPS5430 requires that the output filter components be chosen so that the poles and zeros of the output filter align with the internal compensation pole and zero locations.  For most applications that will mean some type of tantalum or special polyner type capacitor.  That is what these devices are designed to work with.  It may be possible to use other types.  I recommend that you try substituting your desired componenets in switcherpro and check the loop plots for stability.  You can do that by double clicking the output capacitor to pull up teh database, then change to your desired value.  i suspect that these designs will be marginally stable with ceramic output.  You can always add some phase boost at crossover with a feed forward capacitor in parallel with the upper divider resistor.  unfortunately, switcherpro does not support that so you will have to make the calaculations by hand.  there is an app note in teh TPS5430 product page.