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PDF LM27951 Data sheet ( Hoja de datos )
| Número de pieza | LM27951 | |
| Descripción | White LED Adaptive 1.5X/1X Switched Capacitor Current Driver | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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November 2005
www.DataSheet4U.com
LM27951
White LED Adaptive 1.5X/1X Switched Capacitor Current
Driver
General Description
The LM27951 is a switched capacitor white-LED driver ca-
pable of driving up to 4 LEDs with 30mA through each LED.
Its 4 tightly regulated current sources ensure excellent LED
current and brightness matching. LED drive current is pro-
grammed by an external sense resistor. The LM27951 oper-
ates over an input voltage range from 3.0V to 5.5V 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 750kHz
switching frequency optimized for portable applications. The
LM27951 consumes less than 1µA of supply current when
shut down.
The LM27951 is available in a 14-pin No-Pullback Leadless
Leadframe Package: LLP-14.
Features
n Drives up to 4 LEDs with up to 30mA each
n Regulated current sources with 0.2%(typ.) matching
n 3/2x, 1x Gain transition based on LED VF
n Peak Efficiency Over 85%
n Input Voltage Range: 3.0V to 5.5V
n PWM Brightness Control
n Very Small Solution Size - NO INDUCTOR
n Fixed 750kHz Switching Frequency
n <1µA Shutdown Current
n 14-pin LLP Package: 4.0mm X 3.0mm X 0.8mm
Applications
n White LED Display Backlights
n White LED Keypad Backlights
n General Purpose LED Lighting
Typical Application Circuit
© 2005 National Semiconductor Corporation DS201717
20171701
www.national.com
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| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet LM27951.PDF ] | |
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