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Número de pieza | LM2754 | |
Descripción | 800mA Switched Capacitor Flash LED Driver | |
Fabricantes | National Semiconductor | |
Logotipo | ||
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September 2006
LM2754
800mA Switched Capacitor Flash LED Driver with
Time-Out Protection
General Description
The LM2754 is an integrated low noise, high current
switched capacitor DC/DC converter with four regulated cur-
rent sinks. The device is optimized for driving 1 to 4 high
power white LEDs in parallel with a maximum current of
800mA. Maximum efficiency is achieved over the input volt-
age range by actively selecting the proper gain based on the
LED forward voltage and current requirements.
Two external low power resistors set the desired current for
Torch and Flash modes. The TX pin allows the device to be
forced into Torch mode during a Flash pulse, allowing for
synchronization between the RF power amplifier pulse and
Flash/Torch modes. To protect the device and Flash LEDs,
internal Time-Out circuitry turns off the LM2754 in case of a
faulty prolonged Flash mode. Internal soft-start circuitry lim-
its the amount of inrush current during start-up.
The LM2754 is available in a small 24-pin thermally en-
hanced LLP package.
Features
n Up to 800mA Output Current
n Wide Operating Input Voltage Range: 2.8V to 5.5V
n Drives 1, 2, 3 or 4 LEDs in Parallel
n Ability to Disable One Current Sink Via the SEL Pin to
Accommodate 3-LED Flash Modules
n Time-Out Circuitry Limits Flash Duration to 1 Second
n TX Input Ensures Synchronization with RF Power
Amplifier Pulse
n Adaptive 1x, 1.5x and 2x Gains for Maximum Efficiency
n 1MHz Constant Frequency Operation
n Output Current Limit
n True Shutdown Output Disconnect
n <1µA Shutdown Current
n Internal Soft-Start Limits Inrush Current
n No Inductor Required
n Total Solution Size without LED <28mm2
n Low Profile 24-Pin LLP Package (4mm x 4mm x 0.8mm)
Applications
n Camera Flash in Mobile Phones
n Flash for Digital Cameras
n Supplies for DSP’s, Microprocessors, Memory, MP3
Players, Pagers, Other Portable Devices
Typical Application Circuit
© 2006 National Semiconductor Corporation DS202028
20202801
www.national.com
1 page Typical Performance Characteristics Unless otherwise specified: TA = 25˚C, VDx = 1V, V(IN, INSW) =
3.6V, VEN = VIN, VT/F = VTX = VSEL = 0V, CIN = C1 = C2 = 2.2µF, COUT = 4.7µF. Capacitors are low-ESR multi-layer ceramic
capacitors (MLCC’s).
Dx Current vs. RSET
Dx Current vs. Headroom Voltage
20202804
Quiescent Current vs. Input Voltage
20202805
Shutdown Current vs. Input Voltage
20202806
Efficiency vs. Input Voltage
20202807
Oscillator Frequency vs. Input Voltage
20202808
5
20202809
www.national.com
5 Page Physical Dimensions inches (millimeters) unless otherwise noted
24-Pin LLP
NS Package Number SQA24A
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS
WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body, or
(b) support or sustain life, and whose failure to perform when
properly used in accordance with instructions for use
provided in the labeling, can be reasonably expected to result
in a significant injury to the user.
2. A critical component is any component of a life support
device or system whose failure to perform can be reasonably
expected to cause the failure of the life support device or
system, or to affect its safety or effectiveness.
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and Materials of Interest Specification (CSP-9-111S2) for regulatory environmental compliance. Details may be found at:
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11 Page |
Páginas | Total 11 Páginas | |
PDF Descargar | [ Datasheet LM2754.PDF ] |
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