[SI-LIST] Re: DC power supply tolerance for target impedance calculation
- From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- To: sij99@xxxxxxxxx
- Date: Fri, 06 Sep 2013 08:32:34 -0400
Jack,
The VRM ripple and set-point accuracy and any uncompensated voltage drop
on the planes should be subtracted from the allowed voltage band given
for your loads and use the remainder to calculate the impedance target.
When your full voltage variation allowance for the load is only 2%, we
cant use a VRM with 2% tolerance, unless you use a more accurate
monitoring circuit adjusting the output voltage to a much better accuracy.
Regards,
Istvan Novak
Oracle
On 9/5/2013 7:29 AM, Jack Si wrote:
> Hi experts,
> Usually for my calculation, I take 5% as tolerance for target impedance
> calculation which includes (Power supply tolerance-2%, AC Ripple Tolerance-2%
> and DC drop across the plane-1%). But for a case, my loads which require 2%
> of accuracy. So I can't take a typical value as 2% for power supply
> tolerance. In power regulator data sheet, I found the values of load
> regulation, line regulation and Maximum ripple. I consider the load
> regulation+line regulation value as power supply tolerance. Isn't right? Or
> should I include any other parameter also...
>
> Thanks,
>
> Jack
>
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