how to get the power switch's size (w/L) in dc-dc converter?

[batistuta]

how to get the power switch's size (w/L) in dc-dc converter?

thanks.

 

[anlgnovice]

Re: how to get the power switch's size (w/L) in dc-dc conver

Why do you need W/L of the power FET.

Generally they only mention RON (ON resistance) of the switch in the data sheets. I dont think you will know unless you are a designer. You can calculate W/L approximately if you know Un && Cox and supply voltages. you can use below eqn to calculate W/L. this should give close value.

RON=1/((Un*cox*(VGS-vth)*(W/L)).

For different technologies it will be different. It also depends whether it is a high voltage switch or low voltgae switch. your question is not clear.

Let's say for 0.5um CMOS process, if you want an 60V switch with 1A capability, W will be in thousands and L is approximately 1.5 - 2.0 (L is bigger because of HV).

 

[batistuta]

Re: how to get the power switch's size (w/L) in dc-dc conver

Why do you need W/L of the power FET.

Generally they only mention RON (ON resistance) of the switch in the data sheets. I dont think you will know unless you are a designer. You can calculate W/L approximately if you know Un && Cox and supply voltages. you can use below eqn to calculate W/L. this should give close value.

RON=1/((Un*cox*(VGS-vth)*(W/L)).

For different technologies it will be different. It also depends whether it is a high voltage switch or low voltgae switch. your question is not clear.

Let's say for 0.5um CMOS process, if you want an 60V switch with 1A capability, W will be in thousands and L is approximately 1.5 - 2.0 (L is bigger because of HV).

thanks,anlgnovice! i know what you mean, the equation is one way to get the W/L,

and if by the way of simulation, how to do ?? can anybody help me out?

thanks.