nud4011 ON Semiconductor, nud4011 Datasheet - Page 4

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

Design Guide for DC Applications
10. Calculate the junction temperature using the
1. Define LED’s current:
2. Calculate Resistor Value for R
3. Define V
4. Define V
5. Calculate Vdrop across the NUD4001 device:
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: per example in Figure 5,
device’s driver:
device’s control circuit per below formula:
Figure 3), then select the most appropriate
recourse and repeat steps 1−8:
thermal information on Page 8 and refer to
Figure 4 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 5, V
a. V
b. V
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
configuration
D_total
LED
D_driver
D_driver
D_driver
D_control
D_control
D_total
D_total
ext
ext
LED
LEDs
drop
drop
drop
= V
= 0.7(T
= 30 mA
in
= V
LED
= 120 V – 0.7 V – 90 V
= 29.3 V
= 3.0 V (30 LEDs in series)
= 90 V
> 1.13 W (or derated value per
:
= P
= 0.879 W + 0.040 W = 0.919 W
sense
out
= V
= 29.3 V
= 0.879 W
in
in
= (V
= 0.040 W
@ I
D_driver
– V
by increasing R
J
drop
(see Figure 2) / I
= 25 °C) / 0.030 = 24 W
LED
in
sense
– 1.4 – V
* I
per LED supplier’s data
+ P
out
– V
0.030 A
D_control
LEDs
LEDs
in
ext
ext
= 120 Vdc
:
LED
)@ / 20,000
APPLICATION INFORMATION
drop
ext
.
http://onsemi.com
4
120 V
PWM
Boost
R
V
ext
in
Figure 5. 120 V Application
1
2
3
4
(Series LED’s Array)
NUD4011
Set Point
Current
8
7
6
5
L
I
I
I
I
out
out
out
out
L
L
ED30
ED1
ED2