LM27951_16 Datasheet, PDF (1/20 Pages) Texas Instruments – White LED Adaptive 1.5/1 Switched-Capacitor Current Driver

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LM27951
SNVS416C – NOVEMBER 2005 – REVISED FEBRUARY 2016
LM27951 White LED Adaptive 1.5×/1× Switched-Capacitor Current Driver
1 Features
•1 Input Voltage Range: 2.8 V to 5.5 V
• Drives up to Four LEDs With up to 30 mA each
• Regulated Current Sources with 0.2% (Typical)
Matching
• 3/2×, 1× Gain Transition Based on LED V_ƒ
• Peak Efficiency Over 85%
• PWM Brightness Control
• Very Small Solution Size - No Inductor
• Fixed 750-kHz Switching Frequency
• < 1-µA Shutdown Current
2 Applications
• White LED Display Backlights
• White LED Keypad Backlights
• General Purpose LED Lighting
3 Description
The LM27951 is a switched capacitor white-LED
driver capable of driving up to four LEDs with 30 mA
through each LED. Its four tightly regulated current
sources ensure excellent LED current and brightness
matching. LED drive current is programmed by an
external sense resistor. The LM27951 operates over
an input voltage range from 2.8 V to 5.5 V and
requires only four low-cost ceramic capacitors.
The LM27951 provides excellent efficiency without
the use of an inductor by operating the charge pump
in a gain of 3/2, or in a gain of 1. Maximum efficiency
is achieved over the input voltage range by actively
selecting the proper gain based on the LED forward
voltage requirements.
The LM27951 uses constant frequency pre-regulation
to minimize conducted noise on the input. It has a
fixed 750-kHz switching frequency optimized for
portable applications. The LM27951 consumes less
than 1 µA of supply current when shut down.
The LM27951 is available in a 14-pin no-pullback
WSON package.
Device Information⁽¹⁾
PART NUMBER
PACKAGE
BODY SIZE (NOM)
LM27951
WSON (14)
4.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Simplified Schematic
V_IN = 3 V to 5.5 V
C_IN
C₁
C₂
R_SET
V_IN
V_OUT
C₁+
C₁-
D4
C₂+
LM27951 _D3
D2
C₂-
D1
I_SET
PWM
GND
EN
C_OUT
I_DX = 30 mA max
D₄
D₃
D₂
D₁
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.