Final Electrical Specifications LT1932 Constant-Current DC/DC LED Driver in ThinSOT July 2001 U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LT®1932 is a fixed frequency step-up DC/DC converter designed to operate as a constant-current source. Because it directly regulates output current, the LT1932 is ideal for driving light emitting diodes (LEDs) whose light intensity is proportional to the current passing through them, not the voltage across their terminals. Up to 80% Efficiency Inherently Matched LED Current Drives Five White LEDs from 2V Drives Six White LEDs from 2.7V Drives Eight White LEDs from 3V Precise, Adjustable Control of LED Current Disconnects LEDs In Shutdown 1.2MHz Fixed Frequency Switching Uses Tiny Ceramic Capacitors Uses Tiny 1mm-Tall Inductors Regulates Current Even When VIN > VOUT Operates with VIN as Low as 1V Low Profile (1mm) ThinSOTTM Package With an input voltage range of 1V to 10V, the device works from a variety of input sources. The LT1932 accurately regulates LED current even when the input voltage is higher than the LED voltage, greatly simplifying batterypowered designs. A single external resistor sets LED current between 5mA and 40mA, which can then be easily adjusted using either a DC voltage or a pulse width modulated (PWM) signal. When the LT1932 is placed in shutdown, the LEDs are disconnected from the output, ensuring a quiescent current of under 1µA for the entire circuit. The device’s 1.2MHz switching frequency permits the use of tiny, low profile chip inductors and capacitors to minimize footprint and cost in space-conscious portable applications. U APPLICATIO S ■ ■ ■ ■ ■ Cellular Telephones Handheld Computers Digital Cameras Portable MP3 Players Pagers , LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. U TYPICAL APPLICATIO Li-Ion Driver for Four White LEDs L1 6.8µH C1 4.7µF 85 D1 6 1 VIN SW LT1932 PWM DIMMING CONTROL 5 SHDN RSET 4 RSET 1.50k LED GND 3 C2 1µF 15mA 80 VIN = 4.2V 75 VIN = 2.7V 70 65 60 2 C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK212BJ105 D1:ZETEX ZHCS400 L1: SUMIDA CLQ4D106R8 OR PANASONIC ELJEA6R8 EFFICIENCY (%) VIN 2.7V TO 4.2V Efficiency 55 0 1932 TA01 5 10 15 LED CURRENT (mA) Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 20 1932 TA02 1 LT1932 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) VIN Voltage ............................................................. 10V SHDN Voltage ......................................................... 10V SW Voltage ............................................................. 36V LED Voltage ............................................................. 36V RSET Voltage ............................................................. 1V Junction Temperature .......................................... 125°C Operating Temperature Range (Note 2) .. – 40°C to 85°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER TOP VIEW SW 1 6 VIN GND 2 5 SHDN LED 3 4 RSET LT1932ES6 S6 PART MARKING S6 PACKAGE 6-LEAD PLASTIC SOT-23 LTST TJMAX = 125°C, θJA = 250°C/ W Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 1.2V, VSHDN = 1.2V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP Minimum Input Voltage MAX 1 V Quiescent Current VRSET = 0.2V VSHDN = 0V 1.2 0.1 RSET Pin Voltage RSET = 1.50k 100 LED Pin Voltage RSET = 1.50k, VIN < VOUT (Figure 1) 120 180 mV LED Pin Current RSET = 562Ω, VIN = 1.5V RSET = 750Ω, VIN = 1.2V RSET = 1.50k, VIN = 1.2V RSET = 4.53k, VIN = 1.2V 38 30 15 5 42 34 17.5 mA mA mA mA LED Pin Current Temperature Coefficient ILED = 15mA Switching Frequency VIN = 1V Maximum Switch Duty Cycle 34 26 12.5 0.8 1.2 90 95 400 mA µA mV – 0.02 ● Switch Current Limit 1.6 1.0 UNITS mA/°C 1.6 MHz % 550 780 mA Switch VCESAT ISW = 300mA 150 200 mV SHDN Pin Current VSHDN = 0V VSHDN = 2V 0 15 0.1 30 µA µA 0.25 V V 5 µA Start-Up Threshold (SHDN Pin) Shutdown Threshold (SHDN Pin) Switch Leakage Current 0.85 Switch Off, VSW = 5V 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. 2 0.01 LT1932 U W TYPICAL PERFOR A CE CHARACTERISTICS Switch Saturation Voltage (VCESAT) Switch Current Limit TJ = 25°C 250 200 TJ = –50°C 150 100 SWITCHING FREQUENCY (MHz) 300 1.8 VIN = 1.2V 600 TJ = 125°C PEAK CURRENT (mA) SWITCH SATURATION VOLTAGE (mV) 350 VIN = 10V 500 400 300 200 100 50 0 Switching Frequency 2.0 700 400 0 100 200 400 500 300 SWITCH CURRENT (mA) 50 25 75 0 TEMPERATURE (°C) 100 LED Pin Voltage LED CURRENT (mA) LED PIN VOLTAGE (mV) 300 TJ = 25°C 150 TJ = –50°C 100 45 35 RSET = 750Ω 30 25 20 RSET = 1.50k 15 35 0 – 50 – 25 40 Quiescent Current 20 RSET = 1.50k 15 RSET = 4.53k 0 75 50 25 TEMPERATURE (°C) 0 100 125 0 2 4 6 INPUT VOLTAGE (V) 8 10 1932 G06 Switching Waveforms SHDN Pin Current 50 45 1.75 VSW 10V/DIV TJ = –50°C 40 1.50 VIN = 10V SHDN PIN CURRENT QUIESCENT CURRENT (mA) 25 1932 G05 2.00 125 RSET = 750Ω 30 5 1932 G04 1.25 1.00 VIN = 1.2V 0.75 0.50 IL1 200mA/DIV VOUT 20mV/DIV AC COUPLED ILED 10mA/DIV 35 TJ = 25°C 30 25 20 TJ = 125°C VIN = 3V 0.5µs/DIV 4 WHITE LEDs ILED = 15mA CIRCUIT ON FIRST PAGE OF THIS DATA SHEET 15 10 0.25 0 – 50 – 25 35 10 RSET = 4.53k 5 15 20 25 30 LED CURRENT (mA) 100 RSET = 562Ω 40 10 50 10 50 25 0 75 TEMPERATURE (°C) LED Current RSET = 562Ω 40 5 0.4 50 45 350 0 0.6 1932 G03 LED CURRENT (mA) 400 0 0.8 LED Current TJ = 125°C VIN = 1.2V 1.0 0 –50 –25 125 50 250 VIN = 10V 1.2 1932 G02 1932 G01 200 1.4 0.2 0 –50 –25 600 1.6 5 75 50 25 TEMPERATURE (°C) 0 100 125 1932 G07 0 0 2 6 8 4 SHDN PIN VOLTAGE (V) 1093 G09 10 1932 G08 3 LT1932 U U U PI FU CTIO S SW (Pin 1): Switch Pin. This is the collector of the internal NPN power switch. Minimize the metal trace area connected to this pin to minimize EMI. RSET (Pin 4): A resistor between this pin and ground programs the LED current (that flows into the LED pin). This pin is also used to provide LED dimming. GND (Pin 2): Ground Pin. Tie this pin directly to local ground plane. SHDN (Pin 5): Shutdown Pin. Tie this pin higher than 0.85V to turn on the LT1932; tie below 0.25V to turn it off. LED (Pin 3): LED Pin. This is the collector of the internal NPN LED switch. Connect the cathode of the bottom LED to this pin. VIN (Pin 6): Input Supply Pin. Bypass this pin with a capacitor to ground as close to the device as possible. W BLOCK DIAGRA D1 L1 VOUT VIN C1 5 SHDN 6 VIN 1 DRIVER SW C2 Q1 + ×5 0.04Ω – 1.2MHz OSCILLATOR + S Σ + 3 LED ILED Q2 DRIVER + Q – A2 R – A1 + LED CURRENT REFERENCE 2 4 GND ISET 1932 F01 RSET RSET Figure 1. LT1932 Block Diagram U OPERATIO The LT1932 uses a constant frequency, current mode control scheme to regulate the output current, ILED. Operation can be best understood by referring to the block diagram in Figure 1. At the start of each oscillator cycle, the SR latch is set, turning on power switch Q1. The signal at the noninverting input of the PWM comparator A2 is proportional to the switch current, summed together with a portion of the oscillator ramp. When this signal reaches the level set by the output of error amplifier A1, comparator A2 resets the latch and turns off the 4 power switch. In this manner, A1 sets the correct peak current level to keep the LED current in regulation. If A1’s output increases, more current is delivered to the output; if it decreases, less current is delivered. A1 senses the LED current in switch Q2 and compares it to the current reference, which is programmed using resistor RSET. The RSET pin is regulated to 100mV and the output current, ILED, is regulated to 225 • ISET. Pulling the RSET pin higher than 100mV will pull down the output of A1, turning off power switch Q1 and LED switch Q2. LT1932 U W U U APPLICATIO S I FOR ATIO Inductor Selection Several inductors that work well with the LT1932 are listed in Table 1. Many different sizes and shapes are available. Consult each manufacturer for more detailed information and for their entire selection of related parts. As core losses at 1.2MHz are much lower for ferrite cores that for the cheaper powdered-iron ones, ferrite core inductors should be used to obtain the best efficiency. Choose an inductor that can handle at least 0.5A and ensure that the inductor has a low DCR (copper wire resistance) to minimize I2R power losses. A 4.7µH or 6.8µH inductor will be a good choice for most LT1932 designs. Table 1. Recommended Inductors PART L (µH) MAX DCR (mΩ) MAX HEIGHT (mm) ELJEA4R7 ELJEA6R8 4.7 6.8 180 250 2.2 2.2 Panasonic (714) 373-7334 www.panasonic.com LQH3C4R7M24 LQH3C100M24 4.7 10 260 300 2.2 2.2 Murata (814) 237-1431 www.murata.com efficiency by up to 12% over the smaller, thinner ones. Keep this in mind when choosing an inductor. The value of inductance also plays an important role in the overall system efficiency. While a 1µH inductor will have a lower DCR and a higher current rating than the 6.8µH version of the same part, lower inductance will result in higher peak currents in the switch, inductor and diode. Efficiency will suffer if inductance is too small. Figure 3 shows the efficiency of the Typical Application on the front page of this data sheet, with several different values of the same type of inductor (Panasonic ELJEA). The smaller values give an efficiency 3% to 5% lower than the 6.8µH value. 85 VENDOR LB2016B4R7 LB2016B100 4.7 6.8 250 350 2.0 2.0 Taiyo Yuden (408) 573-4150 www.t-yuden.com CMD4D06-4R7 CMD4D06-6R8 CLQ4D10-4R7 CLQ4D10-6R8 4.7 6.8 4.7 6.8 216 296 162 195 0.8 0.8 1.2 1.2 Sumida (847) 956-0666 www.sumida.com PANASONIC ELJEA6R8 EFFICIENCY (%) 80 SUMIDA CLQ4D10-6R8 75 SUMIDA CMD4D06-6R8 70 65 TAIYO YUDEN LB2016B6R8 60 TAIYO YUDEN LB2012B6R8 55 0 5 VIN = 3.6V 4 WHITE LEDs ALL ARE 10µH INDUCTORS 10 15 LED CURRENT (mA) 20 1932 F02 Figure 2. Efficiency for Several Different Inductor Types Inductor Efficiency Considerations 80 6.8µH EFFICIENCY (%) Many applications have thickness requirements that restrict component heights to 1mm or 2mm. There are 2mm tall inductors currently available that provide a low DCR and low core losses that help provide good overall efficiency. Inductors with a height of 1mm (and less) are becoming more common, and a few companies have introduced chip inductors that are not only thin, but have a very small footprint as well. While these smaller inductors will be a necessity in some designs, their smaller size gives higher DCR and core losses, resulting in lower efficiencies. Figure 2 shows efficiency for the Typical Application circuit on the front page of this data sheet, with several different inductors. The larger devices improve 85 22µH 4.7µH 75 2.2µH 70 65 VIN = 3.6V 4 WHITE LEDs PANASONIC ELJEA INDUCTORS 60 55 0 5 10 15 LED CURRENT (mA) 20 1932 F03 Figure 3. Efficiency for Several Different Inductor Values 5 LT1932 U W U U APPLICATIO S I FOR ATIO Capacitor Selection Low ESR (equivalent series resistance) capacitors should be used at the output to minimize the output ripple voltage. Because they have an extremely low ESR and are available in very small packages, multilayer ceramic capacitors are an excellent choice. X5R and X7R type capacitors are preferred because they retain their capacitance over wider voltage and temperature ranges than other types such as Y5V or Z5U. A 1µF or 2.2µF output capacitor is sufficient for most applications. Always use a capacitor with a sufficient voltage rating. Ceramic capacitors do not need to be derated (do not buy a capacitor with a rating twice what your application needs). A 16V ceramic capacitor is good to more than 16V, unlike a 16V tantalum, which may be good to only 8V when used in certain applications. Low profile ceramic capacitors with a 1mm maximum thickness are available for designs having strict height requirements. Ceramic capacitors also make a good choice for the input decoupling capacitor, which should be placed as close as possible to the LT1932. A 2.2µF or 4.7µF input capacitor is sufficient for most applications. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information on their entire selection of ceramic parts. Table 2. Recommended Ceramic Capacitor Manufacturers turned off (typically less than one-third the time), so a 0.4A or 0.5A diode will be sufficient for most designs. Table 3. Recommended Schottky Diodes PART VENDOR MBR0520 MBR0530 MBR0540 ON Semiconductor (800) 282-9855 www.onsemi.com ZHCS400 ZHCS500 Zetex (631) 543-7100 www.zetex.com Programming LED Current The LED current is programmed with a single resistor connected to the RSET pin (see Figure 1). The RSET pin is internally regulated to 100mV, which sets the current flowing out of this pin, ISET, equal to 100mV/RSET. The LT1932 regulates the current into the LED pin, ILED, to 225 times the value of ISET. For the best accuracy, a 1% (or better) resistor value should be used. Table 4 shows several typical 1% RSET values. For other LED current values, use the following equation to choose RSET. 0.1V RSET = 225 • ILED Table 4. RSET Resistor Values ILED (mA) RSET VALUE VENDOR PHONE URL 40 562Ω Taiyo Yuden (408) 573-4150 www.t-yuden.com 30 750Ω 1.13k Murata (814) 237-1431 www.murata.com 20 Kemet (408) 986-0424 www.kemet.com 15 1.50k 10 2.26k 5 4.53k Diode Selection Schottky diodes, with their low forward voltage drop and fast switching speed, are the ideal choice for LT1932 applications. Table 3 shows several different Schottky diodes that work well with the LT1932. Make sure that the diode has a voltage rating greater than the output voltage. The diode conducts current only when the power switch is 6 Most white LEDs are driven at maximum currents of 15mA to 20mA. Some higher power designs will use two parallel strings of LEDs for greater light output, resulting in 30mA to 40mA (two strings of 15mA to 20mA) flowing into the LED pin. LT1932 U W U U APPLICATIO S I FOR ATIO Open-Circuit Protection For applications where the string of LEDs can be disconnected or could potentially become an open circuit, a zener diode can be added across the LEDs to protect the LT1932 (see Figure 4). If the device is turned on without the LEDs present, no current feedback signal is provided to the LED pin. The LT1932 will then switch at its maximum duty cycle, generating an output voltage 10 to 15 times greater than the input voltage. Without the zener, the SW pin could see more than 36V and exceed its maximum rating. The zener voltage should be larger than the maximum forward voltage of the LED string. L1 6.8µH D1 VIN 6 1 VIN SW 24V If the RSET pin is used, increasing the duty cycle will decrease the brightness. Using this method, the LEDs are dimmed using RSET and turned off completely using SHDN. If the RSET pin is used to provide PWM dimming, the approximate value of RPWM should be (where VMAX is the “high” value of the PWM signal): V RPWM = RSET • MAX – 1 0.15V In addition to providing the widest dimming range, PWM brightness control also ensures the “purest” white LED color over the entire dimming range. The true color of a white LED changes with operating current, and is the “purest” white at a specific forward current, usually 15mA or 20mA. If the LED current is less than or more than this value, the emitted light becomes more blue. For color LCDs, this often results in a noticeable and undesirable blue tint to the display. LT1932 C1 4.7µF 5 SHDN LED RSET GND 4 2 3 C2 1µF 15mA RSET 1.50k 1932 F04 Figure 4. LED Driver with Open-Circuit Protection Dimming Using a PWM Signal PWM brightness control provides the widest dimming range (greater than 20:1) by pulsing the LEDs on and off using the control signal. The LEDs operate at either zero or full current, but their average current changes with the PWM signal duty cycle. Typically, a 5kHz to 40kHz PWM signal is used. PWM dimming with the LT1932 can be accomplished two different ways (see Figure 6). The SHDN pin can be driven directly or a resistor can be added to drive the RSET pin. If the SHDN pin is used, increasing the duty cycle will increase the LED brightness. Using this method, the LEDs can be dimmed and turned off completely using the same control signal. A 0% duty cycle signal will turn off the LT1932, reducing the total quiescent current to zero. When a PWM control signal is used to drive the SHDN pin of the LT1932 (see Figure 6), the LEDs are turned off and on at the PWM frequency. The current through them alternates between full current and zero current, so the average current changes with duty cycle. This ensures that when the LEDs are on, they can be driven at the appropriate current to give the purest white light. Figure 5 shows the LED current when a 5kHz PWM dimming control signal is used with the LT1932. The LED current waveform cleanly tracks the PWM control signal with no delays, so the LED brightness varies linearly with the PWM duty cycle. VPWM 2V/DIV ILED 10mA/DIV 50µs/DIV 1932 F05 Figure 5. PWM Dimming Using the SHDN Pin 7 LT1932 U W U U APPLICATIO S I FOR ATIO Dimming Using a Filtered PWM Signal Dimming Using a DC Voltage While the direct PWM method provides the widest dimming range and the purest white light output, it causes the LT1932 to enter into Burst ModeTM operation. This operation may be undesirable for some systems, as it may reflect some noise to the input source at the PWM frequency. The solution is to filter the control signal by adding a 10k resistor and a 0.1µF capacitor as shown in Figure 6, converting the PWM to a DC level before it reaches the RSET pin. The 10k resistor minimizes the capacitance seen by the RSET pin. For some applications, the preferred method of brightness control uses a variable DC voltage to adjust the LED current. As the DC voltage is increased, current flows through RADJ into RSET, reducing the current flowing out of the RSET pin, thus reducing the LED current. Choose the RADJ value as shown below where VMAX is the maximum DC control voltage, ILED(MAX) is the current programmed by RSET, and ILED(MIN) is the minimum value of ILED (when the DC control voltage is at VMAX). VMAX – 0.1V RADJ = 225 • ILED(MAX) – ILED(MIN) Dimming Using a Logic Signal For applications that need to adjust the LED brightness in discrete steps, a logic signal can be used as shown in Figure 6. RMIN sets the minimum LED current value (when the NMOS is off): 0.1V RMIN = 225 • ILED(MIN) RINCR sets how much the LED current is increased when the NMOS is turned on: Regulating LED Current when VIN > VOUT The LT1932 contains special circuitry that enables it to regulate the LED current even when the input voltage is higher than the output voltage. When VIN is less than VOUT, the internal NPN LED switch (transistor Q2 in Figure 1) is saturated to provide a lower power loss. When VIN is greater than VOUT, the NPN LED switch comes out of saturation to keep the LED current in regulation. Burst Mode is a trademark of Linear Technology Corporation. 0.1V RINCR = 225 • ILED(INCREASE) LT1932 LT1932 RSET SHDN 5 4 LT1932 RSET 4 RPWM PWM LT1932 RSET 10k RSET 4 RPWM PWM LT1932 RSET RSET 4 RADJ PWM RINCR VDC 0.1µF RSET LOGIC SIGNAL RMIN 1932 F06 PWM PWM FILTERED PWM DC VOLTAGE Figure 6. Five Methods of LED Dimming 8 LOGIC LT1932 U W U U APPLICATIO S I FOR ATIO Board Layout Considerations As with all switching regulators, careful attention must be paid to the PCB board layout and component placement. To maximize efficiency, switch rise and fall times are made as short as possible. To prevent radiation and high frequency resonance problems, proper layout of the high frequency switching path is essential. Minimize the length and area of all traces connected to the SW pin and always use a ground plane under the switching regulator to minimize interplane coupling. The signal path including the switch, output diode D1 and output capacitor C2, contains nanosecond rise and fall times and should be kept as short as possible. In addition, the ground connection for the RSET resistor should be tied directly to the GND pin and not be shared with any other component, ensuring a clean, noise-free connection. Recommended component placement is shown in Figure 7. L1 D1 C2 GND C1 1 6 VIN 2 5 SHDN 3 4 RSET DIMMING CONTROL 1932 F07 Figure 7. Recommended Component Placement U TYPICAL APPLICATIO S 5V Driver for 16 White LEDs Efficiency 80 D1 75 6 1 VIN SW EFFICIENCY (%) L1 10µH VIN 5V 70 65 60 LT1932 C1 4.7µF 5V DC DIMMING CONTROL 5 LED SHDN 51.1k RSET GND 4 2 RSET 750Ω C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN GMK325BJ225 D1: ZETEX ZHCS400 L1: MURATA LQH3C100M24 3 C2 2.2µF 55 50 0 100Ω 100Ω 5 10 15 20 LED CURRENT (mA) 25 30 1932 TA14b 30mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431 1932 TA14a 9 LT1932 U TYPICAL APPLICATIO S Efficiency Single Cell Driver for One White LED L1 4.7µH VIN 1V TO 1.5V 80 D1 75 1 VIN SW VIN = 1.5V LT1932 C1 4.7µF 2.5V PWM DIMMING CONTROL 5 LED SHDN 24.9k RSET GND 4 2 3 C2 4.7µF EFFICIENCY (%) 6 15mA 70 VIN = 1.1V 65 60 55 RSET 1.50k 50 0 C1, C2: TAIYO YUDEN JMK212BJ475 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24 (408) 573-4150 (631) 543-7100 (814) 237-1431 2.5 1932 TA03a L1 4.7µH 80 2.5V PWM DIMMING CONTROL SHDN 24.9k RSET GND 4 2 3 C2 2.2µF 15mA VIN = 1.5V 70 VIN = 1.1V 65 60 55 RSET 1.50k C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN LMK212BJ225 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24 10 LED EFFICIENCY (%) SW LT1932 5 75 1 VIN C1 4.7µF 15 Efficiency D1 6 12.5 1932 TA03b Single Cell Driver for Two White LEDs VIN 1V TO 1.5V 5 7.5 10 LED CURRENT (mA) 50 (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431 0 1932 TA04a 2.5 5 7.5 10 LED CURRENT (mA) 12.5 15 1932 TA04b LT1932 U TYPICAL APPLICATIO S Efficiency 2-Cell Driver for Two White LEDs L1 4.7µH VIN 1.8V TO 3V 85 D1 80 1 VIN SW VIN = 3V LT1932 C1 4.7µF 2.5V DC DIMMING CONTROL 5 LED SHDN 60.4k RSET GND 4 2 3 C2 2.2µF EFFICIENCY (%) 6 15mA 75 VIN = 1.8V 70 65 60 RSET 1.50k 55 0 C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN LMK212BJ225 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24 (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431 5 1932 TA15a L1 4.7µH 20 1932 TA15b 2-Cell Driver for Three White LEDs VIN 1.8V TO 3V 10 15 LED CURRENT (mA) Efficiency 85 D1 80 1 VIN SW VIN = 3V LT1932 C1 4.7µF 2.5V DC DIMMING CONTROL 5 SHDN 60.4k LED RSET GND 4 2 3 C2 2.2µF 15mA EFFICIENCY (%) 6 75 VIN = 1.8V 70 65 60 RSET 1.50k C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK316BJ225 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24 55 (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431 0 1932 TA06a 5 10 15 LED CURRENT (mA) 20 1932 TA06b 11 LT1932 U TYPICAL APPLICATIO S 2-Cell Driver for Four White LEDs L1 4.7µH VIN 1.8V TO 3V Efficiency 85 D1 80 C1 4.7µF 6 1 VIN SW LT1932 PWM DIMMING CONTROL 5 SHDN LED RSET GND 4 2 3 C2 1µF EFFICIENCY (%) VIN = 3V 75 VIN = 1.8V 70 65 15mA 60 RSET 1.50k 55 0 C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK212BJ105 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24 (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431 5 1932 TA07a L1 4.7µH 20 1932 TA07b 2-Cell Driver for Five White LEDs VIN 2V TO 3V 10 15 LED CURRENT (mA) Efficiency 85 D1 C1 4.7µF 6 1 VIN SW LT1932 PWM DIMMING CONTROL 5 SHDN LED RSET GND 4 2 3 C2 1µF EFFICIENCY (%) 80 75 VIN = 3V 70 VIN = 2V 65 60 RSET 1.50k C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK316BJ105 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24 12 55 15mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431 0 1932 TA05a 5 10 15 LED CURRENT (mA) 20 1932 TA05b LT1932 U TYPICAL APPLICATIO S Li-Ion Driver for Two White LEDs L1 6.8µH 85 D1 6 1 VIN SW LT1932 C1 4.7µF 3.3V PWM DIMMING CONTROL 5 RSET GND 4 2 31.6k 3 LED SHDN C2 2.2µF 15mA EFFICIENCY (%) VIN 2.7V TO 4.2V Efficiency 80 VIN = 4.2V 75 VIN = 2.7V 70 65 60 RSET 1.50k 55 0 C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN LMK212BJ225 D1: ZETEX ZHCS400 L1: PANASONIC ELJEA6R8 (408) 573-4150 (408) 573-4150 (631) 543-7100 (714) 373-7334 5 1932 TA08a L1 6.8µH Efficiency 85 D1 VIN = 4.2V 6 1 SW LT1932 C1 4.7µF 3.3V PWM DIMMING CONTROL 5 SHDN 31.6k LED RSET GND 4 2 3 C2 2.2µF 15mA EFFICIENCY (%) 80 VIN 20 1932 TA08b Li-Ion Driver for Three White LEDs VIN 2.7V TO 4.2V 10 15 LED CURRENT (mA) VIN = 2.7V 75 70 65 60 RSET 1.50k 55 0 C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK316BJ225 D1: ZETEX ZHCS400 L1: PANASONIC ELJEA6R8 (408) 573-4150 (408) 573-4150 (631) 543-7100 (714) 373-7334 1932 TA09a 5 10 15 LED CURRENT (mA) 20 1932 TA09b 13 LT1932 U TYPICAL APPLICATIO S Li-Ion Driver for Four White LEDs L1 6.8µH C1 4.7µF 85 D1 6 1 VIN SW LT1932 PWM DIMMING CONTROL 5 LED SHDN RSET GND 4 2 3 C2 1µF EFFICIENCY (%) VIN 2.7V TO 4.2V Efficiency 15mA 80 VIN = 4.2V 75 VIN = 2.7V 70 65 60 RSET 1.50k 55 0 C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK212BJ105 D1: ZETEX ZHCS400 L1: PANASONIC ELJEA6R8 (408) 573-4150 (408) 573-4150 (631) 543-7100 (714) 373-7334 5 1932 TA10a C1 4.7µF Efficiency 85 D1 6 1 VIN SW LT1932 PWM DIMMING CONTROL 5 SHDN RSET GND 4 2 RSET 1.50k C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK316BJ105 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24 14 LED 3 C2 1µF EFFICIENCY (%) VIN 2.7V TO 4.2V 20 1932 TA10b Li-Ion Driver for Five White LEDs L1 4.7µH 10 15 LED CURRENT (mA) 80 VIN = 4.2V 75 VIN = 2.7V 70 65 60 55 15mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431 0 1932 TA11a 5 10 15 LED CURRENT (mA) 20 1932 TA11b LT1932 U TYPICAL APPLICATIO S Li-Ion Driver for Eight White LEDs L1 4.7µH VIN 3V TO 4.2V Efficiency 85 D1 80 1 VIN SW VIN = 4.2V EFFICIENCY (%) 6 LT1932 C1 4.7µF 3.3V DC DIMMING CONTROL 5 LED SHDN RSET GND 4 2 80.6k 3 C2 1µF 75 70 VIN = 3V 65 60 RSET 1.50k C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN GMK316BJ105 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24 55 15mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431 0 1932 TA13a 5 10 15 LED CURRENT (mA) 20 1932 TA13b U PACKAGE DESCRIPTIO S6 Package 6-Lead Plastic SOT-23 (LTC DWG # 05-08-1634) (LTC DWG # 05-08-1636) 2.80 – 3.10 (.110 – .118) (NOTE 3) .20 (.008) A A2 DATUM ‘A’ L NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 2.60 – 3.00 1.50 – 1.75 (.102 – .118) (.059 – .069) (NOTE 3) 3. DRAWING NOT TO SCALE 4. DIMENSIONS ARE INCLUSIVE OF PLATING 5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 6. MOLD FLASH SHALL NOT EXCEED .254mm 7. PACKAGE EIAJ REFERENCE IS: SC-74A (EIAJ) FOR ORIGINAL JEDEL MO-193 FOR THIN PIN ONE ID 1.90 (.074) REF .09 – .20 (.004 – .008) (NOTE 2) A1 SOT-23 (Original) SOT-23 (ThinSOT) A .90 – 1.45 (.035 – .057) 1.00 MAX (.039 MAX) A1 .00 – 0.15 (.00 – .006) .01 – .10 (.0004 – .004) A2 .90 – 1.30 (.035 – .051) .80 – .90 (.031 – .035) L .35 – .55 (.014 – .021) .30 – .50 REF (.012 – .019 REF) .95 (.037) REF .25 – .50 (.010 – .020) (6PLCS, NOTE 2) S6 SOT-23 0401 15 LT1932 U TYPICAL APPLICATIO Li-Ion Driver for Ten White LEDs L1 10µH VIN 2.7V TO 4.2V Efficiency 80 D1 VIN = 4.2V 75 VIN = 2.7V 1 VIN SW LT1932 C1 4.7µF 5 LED SHDN RSET GND 4 2 C2 4.7µF 3 100Ω RSET 750Ω EFFICIENCY (%) 6 100Ω 70 65 60 55 30mA 50 0 C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK325BJ475 D1: ZETEX ZHCS400 L1: MURATA LQH3C100M24 (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431 1932 TA16a 5 10 15 20 25 TOTAL LED CURRENT (mA) 1932 TA16b Li-Ion Driver for Six White LEDs L1 4.7µH VIN 2.7V TO 4.2V Efficiency 85 D1 1 VIN SW LT1932 C1 4.7µF 3.3V DC DIMMING CONTROL 5 SHDN RSET GND 4 2 80.6k 3 LED C2 1µF EFFICIENCY (%) 80 6 30 VIN = 4.2V 75 VIN = 2.7V 70 65 60 RSET 1.50k C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK316BJ105 D1: ZETEX ZHCS400 L1: MURATA LQH3C4R7M24 55 15mA (408) 573-4150 (408) 573-4150 (631) 543-7100 (814) 237-1431 0 1932 TA12a 5 10 15 LED CURRENT (mA) 20 1932 TA12b RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1615 Micropower DC/DC Converter in 5-Lead ThinSOT 20V at 12mA from 2.5V Input, ThinSOT Package LT1617 Micropower Inverting DC/DC Converter in 5-Lead ThinSOT –15V at 12mA from 2.5V Input, ThinSOT Package LT1618 Constant-Current/Constant-Voltage DC/DC Converter Drives 20 White LEDs from Li-Ion, MS10 Package LTC1682 Doubler Charge Pump with Low Noise Linear Regulator 3.3V and 5V Outputs with 60µVRMS Noise, Up to 80mA Output LT1930 1.4MHz Switching Regulator in 5-Lead ThinSOT 5V at 480mA from 3.3V Input, ThinSOT Package LT1931 Inverting 1.2MHz Switching Regulator in 5-Lead ThinSOT – 5V at 350mA from 5V Input, ThinSOT Package LTC3200 Low Noise Regulated Charge Pump 5V Output with Up to 100mA Output 16 Linear Technology Corporation 1932i LT/TP 0701 1.5K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2001