LM2794_14 Datasheet, PDF (1/21 Pages) Texas Instruments – Current Regulated Switched Capacitor LED Supply with Analog and PWM Brightness Control

LM2794, LM2795
www.ti.com
SNVS168K – MAY 2004 – REVISED MAY 2004
LM2794 /LM2795 Current Regulated Switched Capacitor LED Supply with Analog and
PWM Brightness Control
Check for Samples: LM2794, LM2795
FEATURES
1
•2 Regulated current sources with ±0.5%
matching between any two outputs
• High efficiency 3/2 boost function
• Drives one, two, three or four white LEDs
• 2.7V to 5.5V Input Voltage
• Up to 80mA output current
• Analog brightness control
• Active-low or high shutdown input ('94/95)
• Very small solution size and no inductor
• 2.3µA (typ.) shutdown current
• 325kHz switching frequency (min.)
• Constant Frequency generates predictable
noise spectrum
• Standard Micro SMD-14 package: 2.08mm X
2.403mm X 0.845mm High
• Thin Micro SMD-14 package: 2.08mm X
2.403mm X 0.600mm High
APPLICATIONS
• White LED Display Backlights
• White LED Keypad Backlights
• 1-Cell Li-Ion battery-operated equipment
including PDAs, hand-held PCs, cellular
phones
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 80mA of load current to accommodate four White LEDs. The switching frequency is
325kHz. (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.
Basic Application Circuit
CIN
1PF
C1
C2
VIN
POUT
C1+
1PF
D1
C1-
D2
C2+
1PF
LM2794/95 ^D3
C2-
D4
SD
BRGT
ISET
GND
CHOLD
1PF
LED1
LED2
LED3
LED4
RSET
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2004, Texas Instruments Incorporated