Why more leakage in LVT Cells.. ?

[deepu777]

Hi,
Can anyone pls explain me why does the LVT cells power dissipation(leakage) will be more.. ? how is this different from HVT cells.. ?

 

[ud23]

https://www.edaboard.com/threads/138759/
https://www.edaboard.com/threads/233873/
https://www.edaboard.com/threads/135577/

 

[artmalik]

LVT/SVT/HVT refer the threshold voltage of the devices used in a particular standard cell. Simply put the Vt of the device is altered by the amount of doping, as the leakage is directly dependent on the threshold voltage...the lower the threshold voltage higher is the leakage.

The cells are laid out once and with different device layers mapped to the LVT,HVT or SVT for doping control. This leads to easy swapping of the cells to get different timing along with different leakage.

 

[cmkrishna]

The threshold voltage specified in LVT/SVT/HVT does it refer to stanadard cell or MOSFET charecteristics
what is the relation between Cell and MOS FET Threshold charecteristics

 

[artmalik]

In a regular standard cell: all the devices are of one kind : LVT,SVT or HVT so the cells are also called lvt_nand, svt_nand and so on. it is naming convention which tells the user what VT the devices in the cell are.

 

[deepu777]

Hi artmalik, It's good explanation thank you. As said "threshold voltage decreases Leakage increases" why does this happen..? how Vt and leakage are related.?

 

[dick_freebird]

Subthreshold slope (which often is not monitored or
controlled), mV/decade. Your VT is the mV, 0 is the
minimum gate voltage you can see in normal logic beds.
So you can simply figure how many decades down from
I(@VT, W, L) you are, and the math will show you why.
You can use a dummy value for insight, or a foundry
value for more realism (but good luck getting a worst
case PVT value, consider yourself lucky if the nominal
modeling of it has a basis in fact).

 

[Anand Cool B]

Below the Vt voltage also there will be some amount of current which is known as subtreshold current.So for LVT very small amount of voltage will be enough for the sub treshold current.This subtreshold current is the major factor for leakage in LVT cells.

 

[yuhiub90]

You should have some basic understanding of MOS structure.
Doping concentration -> thickness of depletion region at p-n junction -> barrier potential (voltage threshold) -> leakage current.