LM3432BSQ National Semiconductor, LM3432BSQ Datasheet - Page 13

• Manufacturer Part Number: LM3432BSQ
• Description: LM3432/LM3432B 6-Channel Current Regulator for LED Backlight Application; Package: LLP; No of Pins: 24; Qty per Container: 1000; Container: Reel
• Manufacturer: National Semiconductor

Applications Information
The LM3432/LM3432B provide a simple and handy solution
for LED driving. With only a few external passive components,
DETERMINATION OF EXTERNAL COMPONENTS
The typical application only requires three external compo-
nents. The selection of those components is described in
detail below.
Programming of String Current, IOUT1 to IOUT6
The string current can be programmed by an external resistor,
R
is shown below.
In order to ensure good current regulation over the full oper-
ating temperature range, a high quality resistor with ±1%
tolerance and a low temperature coefficient is recommended.
IREF
. The equation to calculate the resistance of this resistor
FIGURE 4. Typical Application Schematic to Drive 72 White LEDs (@20 mA) (PWM Digital Dimming)
13
an LED panel of up to about 120 white LEDs can be illumi-
nated. A typical application configuration driving six strings
with twelve white LEDs per string is shown in Figure 4.
For the example shown in Figure 4, the string current is 20
mA. Applying to the equation:
Selecting the VCC Output Capacitor, C
For proper operation, a VCC output capacitor (C
least 680 nF is required for stability reason. The recommend-
ed C
VCC
capacitance is 1 µF.
VCC
www.national.com
VCC
30006421
) of at