LM27961 Datasheet, PDF (1/16 Pages) National Semiconductor (TI) – Dual-Display White LED Driver with 3/2x Switched Capacitor Boost

LM27961
www.ti.com
SNVS326 – NOVEMBER 2004
LM27961 Dual-Display White LED Driver with 3/2x Switched Capacitor Boost
Check for Samples: LM27961
FEATURES
1
•2 Drives 4 Individual Common-Anode LEDs with
up to 20mA each for a Main Display Backlight
• Drives 3 Individual Common-Cathode LEDs
with up to 20mA each for a Sub-Display
Backlight
• Independent Resistor-Programmable Current
Setting
• Excellent Current and Brightness Matching
• High-Efficiency 3/2x Charge Pump
• Extended Li-Ion Input: 2.7V to 5.5V
• PWM Brightness Control: 100Hz - 1kHz
• 18-bump Thin Micro SMD Package: (2.1mm x
2.4mm x 0.6mm)
APPLICATIONS
• Mobile Phone Display Lighting
• Mobile Phone Keypad Lighting
• PDAs
• General LED Lighting
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 independently 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 independently 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 3/2×-gain charge pump.
The LM27961 is available in National’s chip-scale 18-bump micro SMD package.
Typical Application Circuit
C1
1 PF
C2
1 PF
V_IN
2.7V to 5.5V
C_IN
1 PF
C1+
C1- C2+
C2-
V_IN
3/2x Charge Pump
(1x when V_IN > 4.7V)
ENA
ENB
P_OUT
LM27961
R_SETA
I_SETA
I_SETB
R_SETB
D1B D2B D3B
D1A D2A D3A D4A
GND
C_POUT
1 PF
Capacitors:
TDK C1608X5R1A105K,
or equivalent
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