NSC LM2792LDX-H, LM2792LD-L, LM2792EVAL Datasheet
LM2792
Current Regulated Switched Capacitor LED Driver with
Analog Brightness Control
General Description
The LM2792 is a CMOS charge-pump voltage doubler and
regulator that provides two regulated current sources. They
are designed to drive two white (or blue) LEDs with matched
currents (within
±
0.3%) to produce balanced light sources
for display backlights. The LM2792 accepts an input voltage
range from 3.0V to 5.8V and maintain a constant current
determined by an external set resistor.
The LM2792 delivers up to 34mA of load current to accommodate two high forward voltage (typically white) LEDs. The
switching frequency is 900kHz (min.) to keep the conducted
noise spectrum away from sensitive frequencies within portable RF devices.
The LM2792 offers full off to maximum current control
through the BRGT pin. The output current linearly tracks the
BRGT pin voltage. The LM2792 is available in active high or
low shutdown versions. The shutdown pin reduces the operating current to 1µA (max.).
The LM2792 is available in a 10 pin leadless leadframe
(LLP) CSP package.
Features
n Output matching of±0.3% (typ.)
n Drives up to two LED’s
n 3.0V to 5.8V Input Voltage
n Up to 34mA output current
n Soft start limits inrush current
n Analog brightness control
n Separate shutdown input
n Very small solution size and no inductor
n 1.4mA typical operating current
n 1µA (max.) shutdown current
n 900kHz switching frequency (min.)
n Linear regulation generates predictable noise spectrum
n LLP-10 package: 3mm X 3mm X 0.8mm
Applications
n White LED Display Backlights
n White LED Keypad Backlights
n 1-Cell Li-Ion battery-operated equipment including
PDAs, hand-held PCs, cellular phones
n Flat Panel Dispalys
Basic Application Circuit
20024201
July 2002
LM2792 Current Regulated Switched Capacitor LED Driver with Analog Brightness Control
© 2002 National Semiconductor Corporation DS200242 www.national.com
Connection Diagram
20024203
Top View
10-Lead LLP
Ordering Information
Order Number Shutdown Polarity NSC Package
Drawing
Package
Marking
Supplied As
LM2792LD-L Active Low LLP-10 SRB 1000 Units, Tape and Reel
LM2792LDX-L Active Low LLP-10 SRB 4500 Units, Tape and Reel
LM2792LD-H Active High LLP-10 SPB 1000 Units, Tape and Reel
LM2792LDX-H Active High LLP-10 SPB 4500 Units, Tape and Reel
LM2792
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Pin Description
Pin Name Function
1 BRGT Variable voltage input controls output current.
2P
OUT
Charge pump output.
3 C1− Connect this pin to the negative terminal of C1.
4 C1+ Connect this pin to the positive terminal of C1.
5 D2 Current source outputs. Connect directly to LED.
6 D1 Current source outputs. Connect directly to LED.
7 GND Power supply ground input.
8V
IN
Power supply voltage input.
9 SD/SD
Shutdown input. Device operation is inhibited when pin is asserted.
10 I
SET
Current Sense Input. Connect resistor to ground to set constant current through LED.
Block Diagram
20024202
LM2792
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