RDS_ON parameter of MOSFET ?

Thread Starter

Mahantesh Teli

Joined Apr 2, 2016
21
Hi Folks,

Can anyone help me to know which parameter decides to achieve the lowest RDS_ON of MOSFET. and every MOSFET manufactures knows that lower RDS_ON is better for designs, but still why cant they achieve the lowest value of it. ?

Why all MOSFETs will have various RDS_ON values.??

That too especially DC DC converter with built in MOSFET will have crazy values, which affects the lot of parameters.

Thanks !
Mahantesh
 

OBW0549

Joined Mar 2, 2015
3,566
Can anyone help me to know which parameter decides to achieve the lowest RDS_ON of MOSFET. and every MOSFET manufactures knows that lower RDS_ON is better for designs, but still why cant they achieve the lowest value of it. ? Why all MOSFETs will have various RDS_ON values.??
I don't think it is possible to provide a simple answer to the questions you have raised, nor is any single factor responsible for determining Rds(on) in a MOSFET. I found the following documents which contain detailed discussions of Rds(on) and what factors contribute to it:

https://www.fairchildsemi.com/application-notes/AN/AN-9010.pdf
https://www.microsemi.com/document-portal/doc_view/14692-mosfet-tutorial
https://www.infineon.com/dgdl/mosfet.pdf?fileId=5546d462533600a4015357444e913f4f
http://www.ixys.com/Documents/AppNotes/IXAN0061.pdf
http://www.aosmd.com/res/application_notes/mosfets/Power_MOSFET_Basics.pdf
http://www.vishay.com/docs/71933/71933.pdf

Perhaps one or more of these will provide the information you're seeking.
 

Papabravo

Joined Feb 24, 2006
21,159
It is just not true that every application requires a minimum value of RDS_ON. On any given MOSFET you can arrange to increase the Vgs to a value which will have the lowest value of RDS_ON possible. Of course you want to be certain you don't exceed the ABSOLUTE MAXIMUM VALUES. As has been said consult the datasheets and design accordingly.
 

crutschow

Joined Mar 14, 2008
34,281
Rds(on) is like other parameter, such as voltage or current rating.
There are tradeoffs to getting the optimum value, and it's not possible to get the maximum/minimum for all values in one device.

Sort of like designing a car with both the best gas mileage and the maximum power.
You can't have one car with both.
 
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