LT1932 Constant-Current DC/DC LED Driver in ThinSOT FEATURES DESCRIPTIO n Up to 80% Efficiency The LT 1932 is a fixed frequency step-up DC/DC converter n Inherently Matched LED Current designed to operate as a constant-current source. Be- n Adjustable Control of LED Current cause it directly regulates output current, the LT1932 is n Drives Five White LEDs from 2V ideal for driving light emitting diodes (LEDs) whose light n Drives Six White LEDs from 2.7V intensity is proportional to the current passing through n Drives Eight White LEDs from 3V them, not the voltage across their terminals. n Disconnects LEDs In Shutdown With an input voltage range of 1V to 10V, the device works n 1.2MHz Fixed Frequency Switching from a variety of input sources. The LT1932 accurately n Uses Tiny Ceramic Capacitors regulates LED current even when the input voltage is n Uses Tiny 1mm-Tall Inductors higher than the LED voltage, greatly simplifying battery- n Regulates Current Even When V > V IN OUT powered designs. A single external resistor sets LED n Operates with V as Low as 1V IN current between 5mA and 40mA, which can then be easily TM n Low Profile (1mm) ThinSOT Package adjusted using either a DC voltage or a pulse width U modulated (PWM) signal. When the LT1932 is placed in APPLICATIO S shutdown, the LEDs are disconnected from the output, n ensuring a quiescent current of under 1m A for the entire Cellular Telephones n circuit. The devices 1.2MHz switching frequency permits Handheld Computers n the use of tiny, low profile chip inductors and capacitors to Digital Cameras n minimize footprint and cost in space-conscious portable Portable MP3 Players n applications. Pagers , LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. TYPICAL APPLICATIO Li-Ion Driver for Four White LEDs Efficiency 85 L1 D1 6.8H V IN V = 4.2V IN 80 2.7V TO 4.2V V = 2.7V IN 75 C1 61 4.7F V SW IN 70 LT1932 PWM 5 3 C2 65 SHDN LED DIMMING 1F CONTROL R GND SET 15mA 60 4 2 R SET 55 1.50k 0 510 15 20 LED CURRENT (mA) C1: TAIYO YUDEN JMK212BJ475 1932 TA01 C2: TAIYO YUDEN EMK212BJ105 1932 TA02 D1:ZETEX ZHCS400 L1: SUMIDA CLQ4D106R8 OR PANASONIC ELJEA6R8 1932f 1 EFFICIENCY (%) U ULT1932 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART V Voltage ............................................................. 10V IN NUMBER TOP VIEW SHDN Voltage ......................................................... 10V SW Voltage ............................................................. 36V SW 1 6 V IN LT1932ES6 GND 2 5 SHDN LED Voltage ............................................................. 36V LED 3 4 R SET R Voltage ............................................................. 1V SET S6 PART MARKING Junction Temperature.......................................... 125 C S6 PACKAGE 6-LEAD PLASTIC SOT-23 Operating Temperature Range (Note 2) .. 40 C to 85 C LTST T = 125 C, q = 250 C/ W JMAX JA Storage Temperature Range ................. 65 C to 150 C Lead Temperature (Soldering, 10 sec).................. 300 C Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes specifications that apply over the full operating temperature range, otherwise specifications are at T = 25 C. V = 1.2V, V = 1.2V, unless otherwise noted. A IN SHDN PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Input Voltage 1V Quiescent Current V = 0.2V 1.2 1.6 mA RSET V = 0V 0.1 1.0 m A SHDN R Pin Voltage R = 1.50k 100 mV SET SET LED Pin Voltage R = 1.50k, V < V (Figure 1) 120 180 mV SET IN OUT LED Pin Current R = 562W , V = 1.5V 33 38 45 mA SET IN R = 750W , V = 1.2V 25 30 36 mA SET IN R = 1.50k, V = 1.2V 12.5 15 17.5 mA SET IN R = 4.53k, V = 1.2V 5 mA SET IN LED Pin Current Temperature Coefficient I = 15mA 0.02 mA/ C LED Switching Frequency V = 1V 0.8 1.2 1.6 MHz IN Maximum Switch Duty Cycle l 90 95 % Switch Current Limit 400 550 780 mA Switch V I = 300mA 150 200 mV CESAT SW SHDN Pin Current V = 0V 0 0.1 m A SHDN V = 2V 15 30 m A SHDN Start-Up Threshold (SHDN Pin) 0.85 V Shutdown Threshold (SHDN Pin) 0.25 V Switch Leakage Current Switch Off, V = 5V 0.01 5 m A SW Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1932E is guaranteed to meet specifications from 0 C to 70 C. Specifications over the 40 C to 85 C operating temperature range are assured by design, characterization and correlation with statistical process controls. 1932f 2 U WWW