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L1937

UTC
Part Number L1937
Manufacturer UTC
Description WHITE LED STEP-UP CONVERTER
Published Apr 12, 2007
Detailed Description UTC L1937 WHITE LED STEP-UP CONVERTER LINEAR INTEGRATED CIRCUIT 2 1 DESCRIPTION The UTC L1937 is a step-up DC/DC con...
Datasheet PDF File L1937 PDF File

L1937
L1937

Overview
UTC L1937 WHITE LED STEP-UP CONVERTER LINEAR INTEGRATED CIRCUIT 2 1 DESCRIPTION The UTC L1937 is a step-up DC/DC converter specifically designed to drive white LEDs with a constant current.
The device can drive two, three or four LEDs in series from a Li-Ion cell.
Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors.
The UTC LT1937 switches at 1.
2MHz, allowing the use of tiny external components.
The output capacitor can be as small as 0.
22 F, saving space and cost versus alternative solutions.
A low 95mV feedback voltage minimizes power loss in the current setting resistor for better efficiency.
3 5 4 SOT-25 1 FEATURES * Inherently Matched LED Current * High Efficiency: 84% Typical * Drives Up to Four LEDs from a 3.
2V Supply * Drives Up to Six LEDs from a 5V Supply * 36V Rugged Bipolar Switch * Fast 1.
2MHz Switching Frequency * Uses Tiny 1mm Tall Inductors * Requires Only 0.
22 F Output Capacitor www.
DataSheet4U.
com SOT-363 *Pb-free plating product number: L1937L APPLICATIONS * Marking code: LTCG * Cellular Phones * PDAs, Handheld Computers * Digital Cameras * MP3 Players * GPS Receivers PIN FUNCTION PIN NO.
PIN NO.
PIN NAME (SOT-25) (SOT-363).
1 2 3 4 5 6 5 Switch Ground Feedback Shutdown Input Supply Ground SYMBOL SW GND FB FUNCTION Connect inductor/diode here.
Minimize trace area at this pin to reduce EMI.
Connect directly to local ground plane.
Reference voltage is 95mV.
Connect cathode of lowest LED and resistor here.
Calculate resistor value according to the formula: RFB = 95mV/ILED Connect to 1.
5V or higher to enable device;0.
4V or less to disable device.
Input Supply Pin.
Must be locally bypassed.
Connect to Pin 2 and to local ground plane SHDN VIN GND UTC UNISONIC TECHNOLOGIES CO.
, LTD.
1 QW-R103-021,A UTC L1937 BLOCK DIAGRAM VIN 5 LINEAR INTEGRATED CIRCUIT FB 3 COMPARATOR VREF 1.
25V 95mV SW 1 ( PIN 6 FOR SOT-363 PACKAGE ) A1 + Rc Cc A2 + DRIVER R ...


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