Prahad has never indicated what precision he is aiming for, with an 8 bit A/D it can not be extreme. If he is trying to suck that last bit of precision out of the A/D it is a much better idea to use a 10/12 bitter and average the readings.

Hi Erik,
Thank you for your reply..

In this design I am aiming for max 7 bit accuracy from my opAmp rectifer + PCF8591 ADC setup. I am using P89V51RD2 clocked at 8MHz and reading ADC at 3KSPS. The board is well designed with solid ground plane on both the sides of a 2 layer board. Allmost all the traces [ 90% ] are gaurded and all high speed traces are well gaurded. But in my next design I will be using 12 bit ADC and I want to keep myself prepared for this that's why I want to know more about this proper Plane routing.

Regards,
Prahlad Purohit.