STRVS parameters

AN4209

6/19

DocID023949 Rev 2

Equation 3

Equation 4

This model will be useful to assess the power dissipation of the device.

1.2

Thermal parameters

1.2.1

Steady state parameters

The thermal resistance represents the package's dissipation capability from the junction

(active die surface) to a specified reference point (case, lead, board, ambient, etc…). Its

value is defined as the temperature difference between two specified points, divided by the

dissipated power under thermal equilibrium conditions.

Equation 5

Where:

The previous equation can be easily reworked to estimate the junction temperature in

steady mode operation as shown in Equation 6.

Equation 6

thermal resistances are commonly provided to help designers. These parameters are

determined under standard test conditions with specific board dimensions and layers in

compliance with the JEDEC standard.

Table 1 shows typical thermal resistances for available packages.

1

2

1

1

2

2

2

1

)

;

(

)

;

(

)

;

;

(

PP

PP

j

PP

CL

j

PP

CL

J

PP

PP

D

I

I

T

I

V

T

I

V

T

I

I

R

-

-

=

1

2

1

1

1

2

1

0

)

;

;

(

)

;

(

)

;

;

(

PP

j

PP

PP

D

j

PP

CL

j

PP

PP

CL

I

T

I

I

R

T

I

V

T

I

I

V·

-

=

Junction-to-reference thermal resistance expressed in °C/W

Average dissipated power of the die, expressed in W

Junction temperature of the die expressed in °C

Temperature of the reference point expressed in °C

D

f

j

f

j

TH

P

T

T

R

Re

)

Re

(

-

=

-

f

D

f

j

TH

j

T

P

R

T

Re

)

Re

(

+

·

=

-