The difference between KSVR and PSRR parameters

[chang830]

Hi,
For some Class-d audio amplifier, I found the PSRR and KSVR specifications in the datasheet. I wonder what is the descranpancy between these twp specs?

Thanks a lot

 

[rockycheng]

ac psrr measurement

PSRR and KSVR are used to evaluate the rejection abilities to DC and AC variations of the power supply respectively. So PSRR is always a value, and KSVR is a figure with spectrum.

 

[chang830]

class d psrr

PSRR and KSVR are used to evaluate the rejection abilities to DC and AC variations of the power supply respectively. So PSRR is always a value, and KSVR is a figure with spectrum.

thanks rockycheng for the reply.

I am still a bit puzzled by it because I also found some datasheet/articles gives the PSRR a figure vs. freq.

If I sweep the freq from DC-high freq and monitor the output variation rejections vs. supply, is that gives the PSRR and KSVR both?Why we put it apart.

BTW, what the KSVR stand for?

Thanks

 

[safwatonline]

ksvr power sully

Supply voltage rejection,

 

[chang830]

ac psrr vs dc psrr

Supply voltage rejection,

Thanks safwatonline!

Then what "K" stand for?

 

[rockycheng]

using psrr from datasheet

PSRR should only be measured at 0 Hz. You change the supply voltage, and read the variation of the output.

KSVR is actually an AC PSRR measurement using a sweep over the audio frequency range.

 

[safwatonline]

The KSVR vs. PSRR

the K doesn't stand for any thing , actually the SVR is subscribt to the symbol K , just like Kvco.

 

[ytliang]

Re: using psrr from datasheet

PSRR should only be measured at 0 Hz. You change the supply voltage, and read the variation of the output.

KSVR is actually an AC PSRR measurement using a sweep over the audio frequency range.

Your definition of PSRR sounds like line regulation

 

[dick_freebird]

The KSVR vs. PSRR

Often a "K" factor is a forward gain while PSRR is its
dB-scale inverse (rejection ratio).

 

[watersky]

The KSVR vs. PSRR

the below is from TI

The supply rejection ratio, kSVR, is the same as the power supply rejection ratio, PSRR. It is defined as the absolute value of the ratio of the change in supply voltages to the resulting change in input offset voltage. Typically both supply voltages are varied symmetrically. It is expressed in dB.

The power voltage affects the bias point of the input differential pair. Because of the inherent mismatches in the input circuitry, changing the bias point changes the offset voltage, which, in turn, changes the output voltage.

For a dual-supply op amp, kSVR = DVCC�/DVOS or DVDD�/DVOS. The term DVCC� means that the plus and minus power supplies are changed symmetrically. For a single-supply op amp, kSVR = DVCC/DVOS or DVDD/DVOS. Also note that the mechanism that produces kSVR is the same as for CMRR. Therefore kSVR as published in the data sheet is a dc parameter like CMRR. When kSVR is graphed vs. frequency, it falls off as the frequency increases.