LM2794 Datasheet | National Semiconductor

LM2794/LM2795 Current Regulated Switched Capacitor LED Supply with Analog and PWM Brightness Control May 2003 LM2794/LM2795 Current Regulated Switched Capacitor LED Supply with Analog and PWM Brightness Control General Description The LM2794/95 is a fractional CMOS charge-pump that provides four regulated current sources. It accepts an input voltage range from 2.7V to 5.5V and maintains a constant current determined by an external sense resistor. The LM2794/5 delivers up to 80m A of load current to acmodate four White LEDs. The switching frequency is 325k Hz. (min.) to keep the conducted noise spectrum away from sensitive frequencies within portable RF devices. Brightness can be controlled by both linear and PWM techniques. A voltage between 0V and 3.0V may be applied to the BRGT pin to linearly vary the LED current. Alternatively, a PWM signal can be applied to the SD pin to vary the perceived brightness of the LED. The SD pin reduces the operating current to 2.3µA (typ.) The LM2794 is shut down when the SD pin is low, and the LM2795 is shut down when the SD pin is high. The LM2794/95 is available in a micro SMD-14 CSP package. Features n Regulated current sources with ± 0.5% matching between any two outputs n High efficiency 3/2 boost function n Drives one, two, three or four white LEDs n 2.7V to 5.5V Input Voltage n Up to 80m A output current n Analog brightness control n Active-low or high shutdown input (’94/95) n Very small solution size and no inductor n 2.3µA (typ.) shutdown current n 325k Hz switching frequency (min.) n Constant Frequency generates predictable noise spectrum n Standard Micro SMD-14 package: 2.08mm X 2.403mm X 0.845mm High n Thin Micro SMD-14 package: 2.08mm X 2.403mm X 0.600mm High 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 Basic Application Circuit © 2003 National Semiconductor Corporation DS200285 .n...