nud4330 ON Semiconductor, nud4330 Datasheet - Page 7

• Manufacturer Part Number: nud4330
• Description: Three Channel Linear Led Driver
• Manufacturer: ON Semiconductor

Theory of Operation
Each channel is comprised of a FET controlled by a current
limit circuit that senses the voltage drop across the Rsense
resistor and compares it with an internal bandgap voltage
reference (0.5 V) to provide the current regulation.
Current Limit Circuit
reference of 0.5 V. Then the value of the sense resistor
(R
Each of the three channels can be set independently for I
using the same formula.
CSD Circuit
quiescent current when the device is in its non-operational
state (all enables low). This is extremely important in
particular for Li-Ion battery based applications (LapTops
and portables). Figure 11 shows the equivalent circuit for
CSD
This device contains three linear LED current sources.
The current limit circuit contains a bandgap voltage
The circuit shutdown delay (CSD) allows for low
sense
) is calculated by simply using the ohms law formula:
R
sense
+
0.5 V
I
LED
Figure 10. PWM Waveforms (V
APPLICATIONS INFORMATION
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(eq. 1)
NUD4330MN
LED
7
CC
Depending on how the CSD pin is connected, the CSD
circuit can be configured for three different options:
•
•
•
The delay capacitor is connected between CSD pin and
ground and is calculated using the following formula:
= 24 V, R
CSD pin open = immediate shutdown
CSD pin grounded = No shutdown
External capacitor = Delay before shutdown
C
PWM Signal
VDS1
Vsense1
Iout1
delay
sense
+
= 10 W, 1%)
Circuit
CSD
CSD
Figure 11. CSD Circuit
t
delay
7.0 V
10
7 V
E*6
10mA
A
+
-
(eq. 2)