nud4011 ON Semiconductor, nud4011 Datasheet - Page 8

• Manufacturer Part Number: nud4011
• Description: Low Current Led Driver
• Manufacturer: ON Semiconductor

NUD4011 Power Dissipation
size. This can vary from the minimum pad size for soldering
to a pad size given for maximum power dissipation. Power
dissipation for a surface mount device is determined by
T
R
ambient, and the operating temperature, T
values provided on the data sheet for the SO−8 package, P
can be calculated as follows:
ratings table on the data sheet. Substituting these values into
the equation for an ambient temperature T
calculate the power dissipation of the device which in this
case is 1.13 W.
FR−4 copper board with an area of 2 square inches with 2 oz
coverage to achieve a power dissipation of 1.13 W. There are
other alternatives to achieving higher dissipation from the
SOIC package. One of them is to increase the copper area to
J(max)
qJA
The power dissipation of the SO−8 is a function of the pad
The values for the equation are found in the maximum
The 110°C/W for the SO−8 package assumes the use of a
0.000001
250
200
150
100
, the thermal resistance from the device junction to
50
, the maximum rated junction temperature of the die,
0
P D + 150°C * 25°C
0.00001
P D +
110°C
T Jmax * T A
R qJA
0.0001
+ 1.13 W
A
of 25°C, one can
0.001
Figure 12. Transient Thermal Response
A
THERMAL INFORMATION
. Using the
http://onsemi.com
0.01
D
TIME (sec)
8
1S −681.0 sq. mm −1.056 in sq.
reduce the thermal resistance. Figure 11 shows how the
thermal resistance changes for different copper areas.
Another alternative would be to use a ceramic substrate or
an aluminum core board such as Thermal Clad®. Using a
board material such as Thermal Clad or an aluminum core
board, the power dissipation can be even doubled using the
same footprint.
180
160
140
120
100
80
60
1S −321.5 sq. mm −0.498 in sq.
0.1
0
1S −150.0 sq. mm −0.233 in sq.
1
Figure 11. qJA versus Board Area
1S −75.8 sq. mm −0.117 in sq.
2
1
3
BOARD AREA (in
1S −1255.0 sq. mm −1.945 in sq.
4
1S −36.9 sq. mm −0.057 in sq.
10
5
6
2
)
7
100
8
9
1000
10