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Original question:

TPS543B20: Average modelling

TPS543B20: TPS543B20 transient performance issue

Gary Teng
Genius 5850 points
Part Number: TPS543B20

Hi all,

 My customer want to improve TPS543B20 transient performance to compete with IR3895 and they try to modify RAMP circuit as EVM. Would you please helping to provide calculation tool so customer can modify evm's setting to test? Thanks.

VIN

12

V

VOUT

5

V

D

0.416667

IOUT

15

A

FSW

500

KHZ

Best regards,

Gary Teng

gary.teng@arrowasia.com

  • 0
    TI__Guru 56965 points

     

     The TPS543B20 ramp selection resistor table is on page 16 of the datasheet - http://www.ti.com/lit/ds/symlink/tps543b20.pdf#page=16

    The larger Cramp, the smaller the internal ramp will be and the faster the transient response will be.  Including a voltage feedforward capacitor (C22 in the above schematic) will impose more of the output voltage directly on the feedback pin, also increasing the transient response, this is especially effective for a 5V output that would have a large Vout to RSP divider ratio.

    Rramp = 187kOhms is the second highest Cramp value.  Furthering increasing the loop response will require removing the Ramp resistor (R2) to select the largest Cramp capacitor, or reducing the inductor value to speed up the loop response.