AN2657

Model description and parameter extraction

9/18

Equation 22

Equation 23

The remaining model parameters are the capacitances Cgs and Cgd of the MOSFET. The

gate-source capacitance is modeled with a constant capacitance, because it is related to a

highly doped MOSFET (Equation 24).

Equation 24

Moreover, the gate-drain capacitance can be considered as a classic MOSFET model

capacitance, where the equations of the charged capacitance (Equation 25, 26, 27, 28) can

be divided into four regions (Figure 3). Even in this case, capacitance variation depends on

temperature (Equation 29).

Equation 25

Equation 26

Equation 27

Equation 28

Ibv

I

BV

I

s

BV

V

T

--------

⋅

⎩

⎪

⎨

⎪

⎧

=

I

BV

0A

>

I

BV

0A

≤

f1

CjT

VjT

⋅

1MJ

–

---------------------------

=

Qd

TT

Id

f1

1

1Vd

–

VjT

-----------------

⎝⎠

⎛⎞

1MJ

–

()

+

⎝⎠

⎛⎞ CjlparT Vd

⋅

+

⋅

+

⋅

=

f1

CjT

1FCP

–

()

1MJ

–

()

--------------------------------------------

=

f2

1

FCP

1

MJ

+

()

⋅

–

=

Qd

TT

Id

f1

f2

Vd

0.5

MJ

Vd

2

⋅

VjT

--------------------------

⋅

+

⋅

⎝⎠

⎛⎞ CjlparT Vd

⋅

+

⋅

+

⋅

=

⎩⎭

⎪⎪

⎪⎪

⎪⎪

⎪⎪

⎪⎪

⎪⎪

⎨⎬

⎪⎪

⎪⎪

⎪⎪

⎪⎪

⎪⎪

⎪⎪

⎧⎫

-

-

V

D

FCP

≤

V

D

FCP

>

Qgs

CgsT

Vgs

⋅

=

Cgd

Cgx0

1

Vgx

VFB

–

Vjx

-----------------------------

–

⎝⎠

⎛⎞

Mjx

----------------------------------------------------

CgdovlT

+

=

Qgd

Cgx0

Vjx

⋅

1Mjx

–

-------------------------------

1

VFB

Vjx

------------

+

⎝⎠

⎛⎞

1Mjx

–

1

VFB

Vgx

–

Vjx

-----------------------------

+

⎝⎠

⎛⎞

1Mjx

–

–

⎝⎠

⎛⎞ CgdovlT Vgd

⋅

+

⋅

=

Qgd

Cgx0

Vgd

VFB

–

()

Cgx0

Vjx

⋅

1Mjx

–

-------------------------------

1

VFB

Vjx

------------

+

⎝⎠

⎛⎞

1Mjx

–

1

–

⎝⎠

⎛⎞ CgdovlT Vgd

⋅

+

⋅

+

⋅

=

Cgd

Cgx0

1

Vgx

VFB

–

Vjx

-----------------------------

–

⎝⎠

⎛⎞

Mjx

----------------------------------------------------

CgdovlT

+

=

Qgd

Cgx0

VFB

Cgx0

Vjx

⋅

1Mjx

–

-------------------------------

1

VFB

Vgx

–

Vjx

-----------------------------

+

⎝⎠

⎛⎞

1Mjx

–

1

–

⎝⎠

⎛⎞ CgdovlT Vgd

⋅

+

⋅

+

⋅

=

Cgd

Cgx0

CgdovlT

+

=

Qgd

Cgx0

CgdovlT

+

() Vgd

⋅

=