TPS54561 - compensation

Christoph Klees

Hello,

I'm trying to calculate the compensation Network with the formulas from the datasheet.

Parallel I do a simulation/ calculation with the webbench tool and the result is, that I have great differences for the component values.

Which result is the better one or Do you have more infomations how to do the calculation ?

Kind regards

over 10 years ago

0 Anthony F over 10 years ago

TI__Mastermind 35165 points

Hi Christoph,

Could you show the differences in the calculations?

Typically the datasheet equations are more conservative because they are simplified to make an easier calculation. This can result in a smaller Rcomp and larger Ccomp. On the other hand, WEBENCH uses an actual model of the control loop to find more optimized compensation for the output filter it selects. As a result Rcomp can be larger and Ccomp smaller.

Both methods should give acceptable compensation for a stable loop.

Best Regards,
Anthony

0 Christoph Klees over 10 years ago in reply to Anthony F

Prodigy 220 points

Hi Anthony,

for example, I have the following Inputs :

Vin = 44V, Vout = 5V, Iout = 2A, Cout = 44µF, Resr= 0,035Ohm, fsw = 650kHz, L = 15µH

Webbench : R4 = 33K, C5 = 22nF, C8 = 12pF

Datasheet : R4 = 5K, C5 = 22nF, C8 =330pF

Both Network has different crossover frequencies and Phase margins.

I don't know which one I should choose.

In fact I have no fast changes of the load current, so I prefer the smoother Network. Is this a good idea ?

Kind regards

Christoph

0 Anthony F over 10 years ago in reply to Christoph Klees

TI__Mastermind 35165 points

I recommend using the one from WEBENCH.

0 Christoph Klees over 10 years ago in reply to Anthony F

Prodigy 220 points

Thanks a lot !

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TPS54561 - compensation