LM27961 Datasheet, PDF (1/13 Pages) National Semiconductor (TI) – Dual-Display White LED Driver with 3/2x Switched Capacitor Boost

November 2004
LM27961
Dual-Display White LED Driver with 3/2x Switched
Capacitor Boost
General Description
The LM27961 is a charge-pump-based white-LED driver that
is ideal for mobile phone display backlighting. It is intended
to drive 4 LEDs for a main phone display backlight and 3
LEDs for a sub-display backlight. Regulated internal current
sources deliver excellent current and brightness matching in
all LEDs.
The LED driver current sources are split into two indepen-
dently controlled groups. The primary group (Group A) can
be used to backlight a main phone display with up to 4 LEDs.
The low-side current drivers of Group A accommodate
common-anode-type LEDs. The second group (Group B)
can backlight a secondary display with up to 3 LEDs. The
high-side current drivers of Group B accommodate common-
cathode-type LEDs. Both Group A and Group B can also
drive standard two-terminal LEDs, and provide other general
lighting functions (keypad lighting, fun lighting, etc). The
brightness of the two LED groups can be adjusted indepen-
dently with external resistors.
The LM27961 works off an extended Li-Ion input voltage
range (2.7V to 5.5V). Voltage boost is achieved with a high-
efficiency 3/2x-gain charge pump.
The LM27961 is available in National’s chip-scale 18-bump
micro SMD package.
Features
n Drives 4 Individual Common-Anode LEDs with up to
20mA each for a Main Display Backlight
n Drives 3 Individual Common-Cathode LEDs with up to
20mA each for a Sub-Display Backlight
n Independent Resistor-Programmable Current Setting
n Excellent Current and Brightness Matching
n High-Efficiency 3/2x Charge Pump
n Extended Li-Ion Input: 2.7V to 5.5V
n PWM Brightness Control: 100Hz - 1kHz
n 18-bump Thin Micro SMD Package:
(2.1mm x 2.4mm x 0.6mm)
Applications
n Mobile Phone Display Lighting
n Mobile Phone Keypad Lighting
n PDAs
n General LED Lighting
Typical Application Circuit
© 2004 National Semiconductor Corporation DS201279
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