[time-nuts] Power Supply Noise Affects Thunderbolt 1 PPS

gary lists at lazygranch.com
Tue Feb 28 05:49:22 UTC 2012


Well this is the granddaddy with 3V of dropout. Not much rejection at 
high frequency, but the design is old. Modern LDOs are better, 
especially with P-fet pass device.
> http://www.ti.com/lit/ds/symlink/lm317-n.pdf



On 2/27/2012 9:13 PM, Charles P. Steinmetz wrote:
> Ed wrote:
>
>> So, for best HF noise performance where the input noise may be large,
>> it's best to use a follower or shunt regulator topology, despite the
>> lower efficiency - unless efficiency is more important.
>
> To put it more bluntly, the last time I looked (it has been a while, so
> there may be something new I haven't seen) LDOs were all substantially
> inferior to standard regulators in terms of noise feedthrough and HF
> load regulation. The rule of thumb has always been to avoid LDOs unless
> low dropout was the paramount concern. Has something changed with
> current LDO designs to make them competitive with standard regulators in
> terms of noise feedthrough and HF load regulation?
>
> Best regards,
>
> Charles
>
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