AM8068

Motor Driver ICs

θja junction-to-ambient thermal resistance

277.78℃/W

Ψjt junction-to-top characterization parameter

20.6℃/W



Θja is obtained in a simulation on a JEDEC-standard 1s0p board as specified inJESD-51.



The

Θja number listed above gives an estimate of how much temperature rise is expected if the device was

mounted on a standard JEDEC board.



When mounted on the actual PCB, the

Θja value of JEDEC board is totally different than the Θja value of

actual PCB.



Ψjt is extracted from the simulation data to obtain Θja using a procedure described in JESD-51, which

estimates the junction temperature of a device in an actual PCB.



The thermal characterization parameter,

Ψjt, is proportional to the temperature difference between the top

of the package and the junction temperature. Hence, it is useful value for an engineer verifying device

temperature in an actual PCB environment as described in JEDEC JESD-51-12.



When Greek letters are not available,

Ψjt is written Psi-jt.



Definition:

Where :

Ψjt (Psi-jt) = Junction-to-Top(of the package) °C/W

Tj= Die Junction Temp.

°C

Tt= Top of package Temp at center.

°C

Pd= Power dissipation. Watts

Tt

Tj

P

T

T

d

t

j

jt

/

)

(

−

=

ψ

DFEINITION

:

AMtek semiconductors

May. 2018 V1.1

- 8 -