measurement of PSRR and PSR of a voltage regulator

[sivankumar]

psrr measurement

I have designed a voltage regulator which gives the 1.5V supply which biases the 300MHZ ring oscillator. I need to measure the performance of the voltage regulator. Some one told me that i need to know the PSR at the particular frequency? Also i don't know the difference between PSR and PSRR. Can any one please help me?

Regards,
Sivan

 

[heverlee]

psr psrr

you may use the transfer function analysis taking vdd/vss as input and see what happens at the output

 

[erikl]

psr vs psrr

i don't know the difference between PSR and PSRR.

I guess it's identical. Somebody just forgot the 2nd "R".
Of course it could also mean the Principle of Sufficient Reason https://en.wikipedia.org/wiki/Principle_of_sufficient_reason

 

[Raviprasad_K]

psr, psrr

Hi,

As I understand:

PSR - Power Supply Rejection: Measured at the output of LDO. It is just measured with respect to clean ground and no ratio is taken.
PSRR - Power Supply Rejection Ratio: Measured as the ratio - PSRR=(noise at output of LDO)/(noise applied at input supply)

For more details please visit the following link:
www.powerdesignindia.co.in/STATIC/PDF/200812/PDIOL_2008DEC11_SUPPLY_AN_01.pdf?SOURCES=DOWNLOAD

If it is used for PLL, you may not need to bother for the supply noise frequency which falls within the loop bandwidth of the PLL, as the loop can correct the error. But, any noise above the loop bandwidth is definitely a concern.