threshold voltage variation

[Eman kamel]

Hi every one,
again i am working on 45 nm technology when ITRS reports estimates 40% threshold voltage variability
it also mention that the threshold voltage variation reaches 30 % of supply voltage
for VDD = 1volt
threshold voltage variation will be 30 mv
PTM technology model mention vth = 180 mv for 45 nm
if i divide the 30mv/180mv , i can not find the 40 % variation
so what is wrong in my calculation?
thanks in advance
Eman

 

[erikl]

... what is wrong in my calculation?

1V*30%=300mV ; 300mV/180mV=167%

 

[Eman kamel]

1V*30%=300mV ; 300mV/180mV=167%

sorry threshold voltage variability is 3 % not 30 %

 

[erikl]

sorry threshold voltage variability is 3 % not 30 %

May be ±3% is meant? Then you'd have ±16.67% or 33.3% in total -- not too far away.