Monday, 31 August 2015

IR Drop

IR Drop

Voltage transfer in metal a drop occurs due to resistance of metal this is known as IR drop.

 IR drops are two types


1. Static IR drop

    Independent of the cell switching the drop is calculated with the help of wire                            resistance. Methods to Improve static IR drop

     1. Increase the width of wire

     2. Provide more number of wire

                

 2 . Dynamic Power Drop

      Dynamic IR drop:ir drop is calculated with the help of the switching of the cells.           We can improve dynamic IR drop by below methods:      

      1. Placing dcap cells in between them

      2. Increase the no of straps.


Calculation related to IR drop


 1. Average Current Through Each Strap=Istrapavg=(Itotal)/(2*Nstraps)mA


 2. Appropriate Ir Drop At The Center Of The Strap=Vdrop or IRdrop

                                                                                     =IstrapAvg*Rs*(W/2)*(1/Wstrap)  

                                                 

 3. Number Of Straps Between Two Power Pads


     Nstrappinspace=Dpadspacing/Lspace.

     MIN Ring Width = wring = Ip/Rj Microm

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