Announcements

# What does the Mosfet (dVth=0 dRdson=0 dgfs=0 dC=0 dVbr=0) parameters means in Ltspice model library and is Rdson vs Vgs vs Id behaviour included in models?

## What does the Mosfet (dVth=0 dRdson=0 dgfs=0 dC=0 dVbr=0) parameters means in Ltspice model library and is Rdson vs Vgs vs Id behaviour included in models?

Level 1
Level 1

Hello Team,

I am trying to estimate switching losses of Mosfet IAUC120N04S6N013_L1 (model) in buck-boost configuration driving a 12V/5A load using LTspice.

1. Does the model include the Current dependant Rdson behaviour of the mosfet datasheet ?

2. what does dVth=0 dRdson=0 dgfs=0 dC=0 dVbr=0 Ls=0.05n Ld=1n Lg=3n parameters mean?

For example: Does keeping dRdson = 3.2mOhm means the mosfet has Rdson value of 3.2mOhm ?

1 Solution

## Re: What does the Mosfet (dVth=0 dRdson=0 dgfs=0 dC=0 dVbr=0) parameters means in Ltspice model library and is Rdson vs Vgs vs Id behaviour included in models?

Moderator
Moderator

Hi,

Thank you for posting on the Infineon community.

1) Does the model include the Current dependant Rdson behaviour of the mosfet datasheet ?
Soln: The basic behaviour of the MOSFET is that the Rdon varies with Vgs and inturn the Id depends on the Rdson. This behaviour can be seen in the mosfet model.

2) what does dVth=0 dRdson=0 dgfs=0 dC=0 dVbr=0 Ls=0.05n Ld=1n Lg=3n parameters mean?
Soln: OptiMOS model parameters are chosen to give the behaviour of a typical device. However, in order to enable worst-case and sensitivity analyses, OptiMOS models provide several important parameters to the user. Generally, the deviations are scaled to the range [-1;1] where a value of –1 refers to the minimum value, 0 is the typical value (default) and 1 accounts for the maximum value of the model parameter. Note that the parameters have different priorities, such that not all combinations are possible.
Variations of the transconductance are modelled with the parameter dgfs which has a range of [-1;0].
The next parameter is dRdson, which enables the user to consider the maximum onstate resistance of the device. The allowed range is [0;1]. If dRdson≠0, entries in dgfs are overwritten.
Models have the attribute dVth to model threshold voltage deviations from the typical value. The allowed range is [-1;1]. If dVth≠0, entries in dgfs and dRdson are set to zero.
Variations in the capacitances are considered by assigning a value to dC, where values in the range [0;1] are possible.
Furthermore, level 3 models also have the parameter dZth, where values in the range [0;1] are allowed to vary between typical and guaranteed thermal performance.
The parameters of dual devices are accessible individually and named dVth1, dVth2, dgfs1, dgf2, etc.
The modelling of device performance deviations is a complex task since typically there is no one-to-one relation between a deviation in the manufacturing process and the variation in a particular device parameter. The use of the given optional parameters does therefore not account for all cases and might in special cases even result in performance that does not fulfil the specifications guaranteed by Infineon.

Regards,
Abhilash P

3 Replies

## Re: What does the Mosfet (dVth=0 dRdson=0 dgfs=0 dC=0 dVbr=0) parameters means in Ltspice model library and is Rdson vs Vgs vs Id behaviour included in models?

Moderator
Moderator

Hi,

Thank you for posting on the Infineon community.

1) Does the model include the Current dependant Rdson behaviour of the mosfet datasheet ?
Soln: The basic behaviour of the MOSFET is that the Rdon varies with Vgs and inturn the Id depends on the Rdson. This behaviour can be seen in the mosfet model.

2) what does dVth=0 dRdson=0 dgfs=0 dC=0 dVbr=0 Ls=0.05n Ld=1n Lg=3n parameters mean?
Soln: OptiMOS model parameters are chosen to give the behaviour of a typical device. However, in order to enable worst-case and sensitivity analyses, OptiMOS models provide several important parameters to the user. Generally, the deviations are scaled to the range [-1;1] where a value of –1 refers to the minimum value, 0 is the typical value (default) and 1 accounts for the maximum value of the model parameter. Note that the parameters have different priorities, such that not all combinations are possible.
Variations of the transconductance are modelled with the parameter dgfs which has a range of [-1;0].
The next parameter is dRdson, which enables the user to consider the maximum onstate resistance of the device. The allowed range is [0;1]. If dRdson≠0, entries in dgfs are overwritten.
Models have the attribute dVth to model threshold voltage deviations from the typical value. The allowed range is [-1;1]. If dVth≠0, entries in dgfs and dRdson are set to zero.
Variations in the capacitances are considered by assigning a value to dC, where values in the range [0;1] are possible.
Furthermore, level 3 models also have the parameter dZth, where values in the range [0;1] are allowed to vary between typical and guaranteed thermal performance.
The parameters of dual devices are accessible individually and named dVth1, dVth2, dgfs1, dgf2, etc.
The modelling of device performance deviations is a complex task since typically there is no one-to-one relation between a deviation in the manufacturing process and the variation in a particular device parameter. The use of the given optional parameters does therefore not account for all cases and might in special cases even result in performance that does not fulfil the specifications guaranteed by Infineon.

Regards,
Abhilash P

## Re: What does the Mosfet (dVth=0 dRdson=0 dgfs=0 dC=0 dVbr=0) parameters means in Ltspice model library and is Rdson vs Vgs vs Id behaviour included in models?

Level 1
Level 1

Hello Abhilash,

For example:

In datasheet given as :

Rdson( GS=10V, ID=60A) - 1.02(typ)  1.34(max)

in Ltspice simulation I am putting as follows

dgfs = -1, (how can I extract this value from datasheet i.e from transfer characteristics)

dRdson = 0.5,  means that model has Rdson in between 1.02 and 1.34 mOhms and it computes and overwrites dgfs to a new value based on the given dRdson value ?

## Re: What does the Mosfet (dVth=0 dRdson=0 dgfs=0 dC=0 dVbr=0) parameters means in Ltspice model library and is Rdson vs Vgs vs Id behaviour included in models?

Moderator
Moderator

Hi,

As i explained in my previous comment, if one of the parameter is a non zero value, then the other 2 parameters are set to zero by default

Regards,
Abhilash P