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54331D

Other Parts Discussed in Thread: TPS54331

I am using tps54331d and i have a circuit of 4.2V output with 2A Iout-max.At 12v input from variable supply it works fine but when i apply 4.9v (5v) it's output is not stable.

Are there any  components readjustment  possible for  4.2V/2A output at 5V Input other than output set point resistors?

switcher-pro tool also gives a circuit when parameters are set for 5V--4.2V/2A,but is this really possible?

 

 

 

 

  • the TPS54331 is designed to operate with low input voltage headroom.  But if you are operating with both low input voltage and low output current, the output may have 2.1 V p-p ripple.  If the BOOT - PH voltage falls below 2.1 V, the device will turn off the internal FET to allow the BOOT cap to recharge.  if the device is in eco-mode, the PH voltage will be at Vout rather than ground, and the BOOT cap cannot charge until Vout falls to Vin-Vout = 2.1 V.  This is probably what you are seeing.  You can either increase the load or add a charge pump circuit.  See http://focus.ti.com/analog/docs/litabsmultiplefilelist.tsp?literatureNumber=slva444&docCategoryId=1&familyId=751

  • The Datasheet describes the maximum output voltage equation for perticular Vin and from this i got around 3.8V(maximum output) for 5V input voltage.And practically my circuit output couldnt go beyond 3.43v.

    Even switcher pro provides circuit for 5v -INPUT and 4V- output.Please suggest me on this.

    Is there any other pin compitible solution for my requirement?

     

     

  • Switcherpro does not account for eco-mode or other esoteric operating modes.  But we have not determined that this is in fact what you are seeing.  can you provide waveforms?