TPS54260 Design Equations

Alan Smith79617

Other Parts Discussed in Thread: TPS54260

Hello,

I'm going through some of the design equations for a new design using the TPS54260 buck converter. In equation 12 and 13 on page 21 it uses a Rhs variable. But the variable is not defined with the rest of the variables. What does this variable correspond to?

A second question I had was regarding the SwitcherPro software. I've gone through the design of my potential supply for the TPS54260 only to find out that I can not change the resistor value that sets the switching frequency. Does anyone know if this can be changed manually? TI's default is 300kHz, but I'd like to run much higher to eliminate the need for a bigger external inductor and cap.

Since I couldn't change the frequency in the SwitcherPro software, I figured I'd tackle the design equations manually only to find that TI didn't define all the equation variables in their datasheet...

Any help would be great.

Thanks, Alan

over 13 years ago

0 JohnTucker over 13 years ago

TI__Guru**** 191445 points

Rhs is the High side FET resistance or RDS(on).

In switcherpro to change the switching frequency you cannot edit the R value directly. You must start a new design and specify the switching frequency in the "advanced inputs" section. Then switcherpro will calculate the required R value.

0 David GUILLEMOT over 12 years ago in reply to JohnTucker

Prodigy 90 points

Hello,

Can you also tell us what is the Voutsc used in equation 13 ?

Thanks

0 JohnTucker over 12 years ago in reply to David GUILLEMOT

TI__Guru**** 191445 points

That is the short circuit output voltage. It will depend on your circuit and how strong the "short" is. I usually use 0.2 V as an estimate.

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TPS54260 Design Equations