How to select to the sawtooth amptitude and EA reference

[cloudfly88]

How to select to the sawtooth amptitude and EA reference in buck or boost ?
for example, some device select fb reference voltage as 0.6V or 0.8V,
and the sawtooth rample amptitude is 0.8V or 1.0V, what is the choice reason?

 

[cloudfly88]

why no people give any advice. thans

 

[FvM]

Hello

The said parameters never have been selection criteria when I choosed converters, I believe, except for the fact, that reference voltage must be less or equal to intended output voltage. The latter is the reason for newer switching controllers having lower reference voltages, it's simply a consequence of todays processors or logic devices lower core voltages.

Oscillator amplitude is mainly defined by internal auxilary voltage regulator, I think (maybe I could be derived from reference voltage, too). On the other hand, using an unneeded low reference voltage switcher for e. g. a 3.3V or 1.8V supply could require more care in PCB layout, cause reference and oscillator nets are more sensitive to ground bounce. But for newer devices, Vref of 0,8 V is a standard and circuit designers are getting used to.

Regards,
Frank