Power Supply Noise Rejection Ratio's (PSRR)

[Dr.H]

Does anyone have access to info on PSRR for logic chips like 74HC74, etc? I have seen suggestions that these figures are as low as 6dB and therefore these chips benefit greatly from the use of clean power supplies.

Can anyone confirm this? Any data I can see?
Thanks
Ryan

 

[Jocko Homo]

Yeah, it is 6 dB.

At the midpoint when one MOSFET turns off while the other turns on.

Jocko

 

[Dr.H]

Hi Jocko,

Yeah, thats what I have heard before. Any data sheets, etc to back-up that claim?

 

[Jocko Homo]

There are no data sheets to back that up. Just the assumption that the P- and N-channel devices are idntical. If they are not, then it is more than 6 dB in one direction, and much less in the other.

(Hint: It acts like a voltage divider.)

Jocko

 

[Guido Tent]

There are no data sheets to back that up. Just the assumption that the P- and N-channel devices are idntical. If they are not, then it is more than 6 dB in one direction, and much less in the other.

(Hint: It acts like a voltage divider.)

Jocko

My measurements on various manufacturers show indeed about 6 dB. Jocko, most outputs are made symmetrical by scaling the FETs such that N and P side become "identical".