nud4001 ON Semiconductor, nud4001 Datasheet - Page 4

• Manufacturer Part Number: nud4001
• Description: High Current Led Driver
• Manufacturer: ON Semiconductor

Design Guide
10. Calculate the junction temperaure using the
1. Define LED’s current:
2. Calculate Resistor Value for R
3. Define V
4. Define V
5. Calculate V
6. Calculate Power Dissipation on the NUD4001
7. Establish Power Dissipation on the NUD4001
8. Calculate Total Power Dissipation on the device:
9. If P
sheet:
device’s driver:
device’s control circuit per Figure 4:
Figure 3), then select the most appropriate
recourse and repeat steps 1 through 8:
thermal information on Page 7 and refer to Figure
5 to check the output current drop due to the
calculated junction temperature. If desired,
compensate it by adjusting the value of R
a. I
a. R
b. R
a. Per example in Figure 6, V
a. Per example in Figure 6,
a. V
b. V
c. V
a. P
b. P
c. P
a. P
b. P
a. P
b. P
a. Reduce V
b. Reconfigure LED array to reduce V
c. Reduce I
d. Use external resistors or parallel device’s
V
configuration (see application note AND8156)
D_total
LED
D_driver
D_driver
D_driver
D_control
D_control
D_total
D_total
ext
ext
LED
drop
drop
drop
= V
= 0.7 (T
= 350 mA
in
= V
LED
= 12 V – 0.7 V (T
= 0.8 V
= 3.5 V + 3.5 V + 3.5 V = 10.5 V
> 1.13 W (or derated value per
:
= P
= 0.280 W + 0.055 W = 0.335 W
sense
drop
out
= V
= 0.8 V x 0.350 A
= 0.280 Watts
in
in
= Figure 4, for 12 V input voltage
= 0.055 W
@ I
D_driver
– V
by increasing R
J
across the NUD4001 device:
drop
(see Figure 2) / I
= 25 °C)/ 0.350 = 2.0 W
LED
sense
* I
per LED supplier’s data
+ P
out
– V
D_control
J
LED
= 25 °C) – 10.5 V
in
ext
ext
= 12 V
:
LED
APPLICATION INFORMATION
drop
ext
.
http://onsemi.com
4
12 V
Boost
GND
R
V
ext
in
Figure 6. 12 V Application
1
2
3
4
(Series LED’s Array)
NUD4001
Set Point
Current
8
7
6
5
I
I
I
I
out
out
out
out