help-how much my PSRR of ldo should be in my application?

[lxcpku]

Hi,all
i am designing a ldo now , and it is used in a sim-card for cell-phone. that is ,battery supplies for the ldo. i wonder how much my PSRR of ldo should be in this application.
anyone having this experience could help me ? it is much appreciated. thx a lot .

BTW: the maxmum load current is 20mA, and the current comsumption in standby mode is 20uA of the ldo. So i could improve my GBW too much. the GBW of my ldo is about 1M.
someone said PSRR should be 60db@10k,isnot that too much aggressive? and within the current provided. 60db@1k could be realized. then it will be OK for my applicaion ?

 

[zyyang]

Hi Does the ldo used to supply for the digital circuits?

 

[lxcpku]

yes,the ldo is used to supply for the digital circuits

 

[rogerqin]

Re: help-how much my PSRR of ldo should be in my application

For digital circuits, PSRR is not important.

 

[surianova]

Re: help-how much my PSRR of ldo should be in my application

hi!

i think it much depend on your power supply filter, if your power supply filter roll off at 1 MHz, then your psrr for your LDO design should at least until 1Mhz.

summary is below 1 MHZ, power supply noise take care by LDO.

Above 1 MHZ, power supply noise take care by Power supply filter.

Hope it helps.

 

[strabush]

Re: help-how much my PSRR of ldo should be in my application

40dB is a good practical value at the LDO loop bandwidth.

 

[WindRay]

Re: help-how much my PSRR of ldo should be in my application

My comment is that you need to discuss with the application and marketing guys in your company. Also look at other competitor ICs in market because the marketing guys want the specifications to be close or better to the competitor ICs. Discuss with the application guys to find out what other uses beside for sim-card applications.

The final goal is to design IC that can sell. So discuss with them to finalize the specifications if you have problem defining it or meeting the specifications.