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TPSM41625: RAMP Configuration

Rene DeBacker
Prodigy 60 points
Part Number: TPSM41625

My design specifics are VIN=12V,VOUT=0.9V,Load=24A,Switching Frequency=500KHz.

Table 7.3 in the TPSM41625 (SLVSEW0A – SEPTEMBER 2020 – REVISED DECEMBER 2020) specification states that Rramp=78.7K ohms.

Webench Power Designer circuit state that Rramp=121K ohms.

What is the correct value of Rramp?

Thanks

  • 0
    TI__Expert 5310 points

    Hello,

    I would use the 78.7kohm Ramp resistor with the requisite amount of output capacitance detailed in table 7-3. This table was generated based on extensive characterization of this power module and provides a known point of stability. Also, the TPSM41625 has a built in 78.7kohm ramp setting that can be set by connecting the RAMP_SEL (pin33) to agnd and leaving RAMP (pin 32) open. Therefore, you can also save on BOM count! Although 121kohm will likely work for your application, you may risk increasing the crossover frequency and decreasing phase margin to the point where the device is marginally stable depending on the output capacitance.

    The Webbench model is always a good place to start, but I would heed to the datasheet as the final arbiter in this case involving the TPSM41625.

    Regards,

    Alec Biesterfeld