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LM27951 Datasheet

white-LED 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 Vƒ
• 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
VIN = 3 V to 5.5 V
CIN
C1
C2
RSET
VIN VOUT
C1+
C1-
C2+
LM27951
C2-
D4
D3
D2
D1
ISET
PWM
GND
EN
COUT
IDX = 30 mA max
D3
D2
D1
D4
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.




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LM27951 Datasheet Preview

LM27951 Datasheet

white-LED Driver

No Preview Available !

LM27951
SNVS416C – NOVEMBER 2005 – REVISED FEBRUARY 2016
www.ti.com
Table of Contents
1 Features .................................................................. 1
2 Applications ........................................................... 1
3 Description ............................................................. 1
4 Revision History..................................................... 2
5 Pin Configuration and Functions ......................... 3
6 Specifications......................................................... 4
6.1 Absolute Maximum Ratings ...................................... 4
6.2 ESD Ratings.............................................................. 4
6.3 Recommended Operating Conditions....................... 4
6.4 Thermal Information .................................................. 4
6.5 Electrical Characteristics........................................... 5
6.6 Typical Characteristics .............................................. 6
7 Detailed Description .............................................. 7
7.1 Overview ................................................................... 7
7.2 Functional Block Diagram ......................................... 7
7.3 Feature Description................................................... 7
7.4 Device Functional Modes.......................................... 8
8 Application and Implementation .......................... 9
8.1 Application Information.............................................. 9
8.2 Typical Application ................................................. 10
9 Power Supply Recommendations...................... 12
10 Layout................................................................... 13
10.1 Layout Guidelines ................................................. 13
10.2 Layout Example .................................................... 13
11 Device and Documentation Support ................. 14
11.1 Device Support...................................................... 14
11.2 Documentation Support ........................................ 14
11.3 Community Resources.......................................... 14
11.4 Trademarks ........................................................... 14
11.5 Electrostatic Discharge Caution ............................ 14
11.6 Glossary ................................................................ 14
12 Mechanical, Packaging, and Orderable
Information ........................................................... 14
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision B (May 2013) to Revision C
Page
• Added Device Information and Pin Configuration and Functions sections, ESD Ratings and Thermal Information
tables, Feature Description, Device Functional Modes, Application and Implementation, Power Supply
Recommendations, Layout, Device and Documentation Support, and Mechanical, Packaging, and Orderable
Information sections................................................................................................................................................................ 1
Changes from Revision A (May 2013) to Revision B
Page
• Changed layout of National Data Sheet to TI format ........................................................................................................... 13
2 Submit Documentation Feedback
Product Folder Links: LM27951
Copyright © 2005–2016, Texas Instruments Incorporated


Part Number LM27951
Description white-LED Driver
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