STCS2A Application information
13/18
P
D
= (V
DRAIN
- V
FB
) x I
LED
+ (V
CC
x I
CC
)
basing on this and on the thermal resistance and ambient temperature, the junction
temperature can be calculated as:
T
J
= R
thJA
x P
D
+ T
A
A typical application could be:
– Input voltage: 12 V;
– 3 white LEDs with an typical V
F
= 3.6 V;
– LEDs current: 1000 mA;
– Package: PowerSO-10;
–T
A
= 50 °C;
In this case the drain voltage is given by:
V
DRAIN
= 12 - 3 x 3.6 = 1.2 V
end the power dissipated in the IC is the following:
P
D
= (1.2 - 0.1) x 1 + 12 x 0.5 x 10
-3
= 1.1 W
With a thermal resistance junction-ambient equal to 12 °C/W the junction temperature is:
T
J
= 12 x 1.1 + 50 = 63 °C.
The following pictures show the maximum power dissipation according to the ambient
temperature:
Figure 16. Maximum power dissipation vs T
A
for PowerSO-10
0.00
2.00
4.00
6.00
8.00
10.00
12.00
25 35 45 55 65 75 85 95 105 115 125
[°C]
12
35
R
thJA
[°C/W]
P
DMAX
[W]
P
DMAX
= (T
JMAX
-T
A
)/R
thJA
0.00
2.00
4.00
6.00
8.00
10.00
12.00
25 35 45 55 65 75 85 95 105 115 125
[°C]
12
35
R
thJA
[°C/W]
P
DMAX
[W]
P
DMAX
= (T
JMAX
-T
A
)/R
thJA
