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Entry  Wed Aug 1 17:42:32 2012, Mayank S. Rajguru, Calculation of loop filter parameters (R,C1and C1) for 1 GHz 
    Reply  Mon Aug 6 02:44:00 2012, Stefan Ritt, Calculation of loop filter parameters (R,C1and C1) for 1 GHz 
Message ID: 174     Entry time: Mon Aug 6 02:44:00 2012     In reply to: 173
Author: Stefan Ritt 
Subject: Calculation of loop filter parameters (R,C1and C1) for 1 GHz 

Mayank S. Rajguru wrote:

 Hi,

we are planning to use the DRS4 in our board for 1 GHz sampling and digitization.

I have seen in the data sheet that "For the PLL to work, an external loop filter is required. This filter ensures quick locking and stable operation at the desired sampling frequency".

What formula do you use to calculate the values of R, C1 and C2?

Can we use the same given value for different frequencies?

Thanks,

Mayak

I never worked out an exact formula for the parameters. It also depends if you want a fast locking time, or a low phase jitter of the PLL. A good starting point are the values from the evaluation board:

R = 130 Ohm

C1 = 4.7 nF

C2 = 1 uF

They should work from 800 MHz to 5 GHz.

- Stefan 

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