Datasheet

STA540 Thermal information
Doc ID 13907 Rev 6 15/25
5 Thermal information
In order to avoid the intervention of the thermal protection, placed at T
j
=150° C for thermal
muting and T
j
=160° C for thermal shutdown, it is important to calculate the heatsink thermal
resistance, R
th_HS
, correctly.
The parameters that influence the calculation are:
● maximum dissipated power for the device (P
d max
)
● maximum thermal resistance junction to case (R
th_j-case
)
● maximum ambient temperature T
amb_max
There is also an additional term that depends on the Iq (quiescent current).
5.1 Heatsink specification examples
5.1.1 R
th_HS
calculation for 4 single-ended channels
Given V
S
= 14.4 V, R
L
= 4 Ω x 4 channels, R
th_j-case
= 1.8° C/W, T
amb_max
= 50° C and
P
out
= 4 x 7 W then
the maximum power dissipated in the device is:
and the required thermal resistance of the heatsink is:
5.1.2 R
th_HS
calculation for 2 single-ended channels plus 1 BTL channel
Given V
S
= 14.4 V, R
L
= 2x 2 Ω (SE) + 1x 4 Ω (BTL), P
out
= 2 x 12 W + 1 x 26 W then
the maximum power dissipated in the device is:
and the required thermal resistance of the heatsink is:
P
dmax
NChannel
V
CC
2
2Π
2
R
L
------------------- - 4 2.62 10.5W=⋅=⋅=
R
th_HS
150 T
amb_max
–
P
dmax
--------------------------------------------- - R
th_j-case
150 50–
10.5
---------------------- 1.8 7.7°C/W=–=–=
P
dmax
2
V
CC
2
2Π
2
R
L
------------------- -
2V
CC
2
Π
2
R
L
-------------------- 25.25 10.5 21W=+⋅=+⋅=
R
th_HS
150 T
amb_max
–
P
dmax
---------------------------------------------- R
th_j-case
150 50–
21
---------------------- 1.8 3°C/W=–=–=