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AR# 59116

XAPP1241/XAPP589 - What is the maximum limit of G2/G1?

Description

On page 20 of (XAPP589) v2.2 the limits for G1 and G2 are listed.

However, they are incorrect:


 




Solution

The logic limit of G2 is d21.

However, it would saturate constantly (ovf_ab), so the limit is dependent on the system rather than the logic.
 
In the lab G2 has being set to d20 successfully.

However, for applications requiring a fast lock time, G2 = d18 works successfully, but G2 = d16 should be enough for most.
 
The relation G1<G2-2 must be respected to obtain a stable loop.

The gain is a power of 2, so increasing G2 by 1 will actually double the gain.

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
56136 XAPP589 - XAPP1241 - All Digital VCXO Replacement (PICXO) - Design Assistant / Master Answer Record N/A N/A
AR# 59116
Date Created 01/15/2014
Last Updated 04/14/2016
Status Active
Type General Article
Devices
  • Artix-7
  • Artix-7Q
  • Kintex-7
  • More
  • Kintex-7Q
  • Virtex-7
  • Virtex-7Q
  • SoC
  • XA Zynq-7000
  • Zynq-7000
  • Zynq-7000Q
  • Less