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TLV62585: The start-up voltage of TLV62585

takahiko yokota
Mastermind 7135 points
Part Number: TLV62585

Hi

I got a question form my customer.
I found the following thread.
There are listed that first output voltage step can be reduced as the converter will react faster when output voltage reaches the first target of the soft start ramp by using feed forward capacitor.  
Are there the recommend or min/max value of that feed forward capacitor?

Best regards,
Yokota
  • 0
    TI__Intellectual 1525 points

    Hi Yokota,

    typical values for such feed forward capacitors are in the range of 4.7pF to 47pF. The actual value depends on the output voltage and the converter itself.
    For the TLV62585, 22pF is a good choice.

  • 0 in reply to Bjoern Goerner
    Mastermind 7135 points

    Hi  Björn-san

    Thank you for the information.
    Does the value of  first output voltage step depend on Vout?
    My customer evaluated start-up with Cff=22pF.
    first output voltage step was 0.3V(Vout=1.35V) and 0.5V(Vout2.5V).

    Best regards,
    Yokota

     

  • 0 in reply to takahiko yokota
    TI__Intellectual 1525 points

    Hi Yokota-san,

    during the soft start period, the inductor current is limited. 
    This current limit is constantly increased until it reaches the maximum value of at least 4A (typically 4.6A) at the end of the soft start period.

    Because the limit starts at about 1A, the voltage step at the output is totally normal behavior and the step size is mainly defined by the LC network (especially the output capacitance) connected to the switch pin of the converter: The higher the component values, the lower the voltage step.