H CAT32 EE GEN FR ALO CMOS White LED Driver LE FEATURES A D F R E ETM ■ Low quiescent ground current (0.5mA typical) ■ Drives up to 4 White LEDs in series ■ Power efficiency over 80% ■ Shutdown current less than 1µA ■ Compatible pinout with LT1932 ■ Load fault protection against open-circuits ■ Adjustable output current (up to 40mA) ■ Low value external components ■ High frequency 1.2MHz operation ■ Low profile (1mm) 6-lead SOT23 and TDFN (0.8mm) package ■ Input voltage operation down to 2.0V Ω) high voltage ■ Low resistance (0.5Ω power switch APPLICATIONS ■ Color LCD and keypad backlighting ■ Digital cameras ■ Cellular phones ■ PDAs/Games ■ Handheld terminals ■ Portable MP3 players DESCRIPTION The CAT32 is a DC/DC step up converter that delivers a regulated output current. Operation at a constant switching frequency of 1.2MHz allows the device to be used with very small value external inductor and ceramic capacitors. A high voltage output stage allows up to 4 White LEDs to be driven in series. Series drive provides inherent current matching. LED dimming can be done by using a DC voltage, a logic signal, or a pulse width modulation (PWM) signal. The shutdown input pin allows the device to be placed in power-down mode with “near zero” quiescent current. The CAT32 is targeted to drive multiple white lightemitting diodes (LEDs) connected in series and provides the necessary regulated current to control the brightness and the color purity. An external resistor RSET controls the output current level. LED currents of up to 40mA can be supported over a wide range of input supply voltages from 2V to 7V, making the device ideal for battery-powered applications. In addition to overcurrent limiting protection, the device also includes detection circuitry to ensure protection against open-circuit load fault conditions. The device is available in a low profile (1mm max height) 6-lead thin SOT23 package and in a TDFN (0.8mm max height) package. TYPICAL APPLICATION D1 VIN 2.7V to 4.2V 6 VIN PWM DIMMING CONTROL 1 SW CAT32 5 SHDN LED RSET 4 GND 2 3 15mA SOT23 Pin Numbers C1: Taiyo Yuden JMK212BJ475 C2: Taiyo Yuden EMK212BJ105 D1: Zetez ZHCS400 L1: Sumida CLQ4D106R8 (Panasonic ELJEA6R8) Figure 1. Li-Ion Driver for Four High-Brightness White LEDs © 2004 by Catalyst Semiconductor, Inc. Characteristics subject to change without notice 1 Doc No. 5001, Rev. AC CAT32 ORDERING INFORMATION Tube Quantity Reel Quantity Package Marking Code 6-lead, thin SOT23 — 3000 BD CAT32RD4-TE7 8-pad TDFN (3x3mm) — 3500 CCEM CAT32RD4 8-pad TDFN (3x3mm) 120 — CCEM CAT32TDI-TE7 6-lead thin SOT23, Lead Free — 3000 LL Part Number Package CAT32EKT-TE7 PIN CONFIGURATION SW 1 GND 2 LED 3 CAT32 6 VIN 5 SHDN 4 RSET 6-Lead SOT-23 1mm maximum height Power 1 GROUND 8 SW VIN 2 7 NC SHDN 3 6 LED RSET 4 5 GND (Top View) TDFN Package: 3mm x 3mm 0.8mm maximum height (RD4) θ [Free Air] PIN DESCRIPTIONS Pin Number SOT23 Pin Number TDFN Name 1 8 SW 2 5 GND Ground pin. Connect pin 2 to ground. 3 6 LED LED (cathode) connection pin. 4 4 RSET RESET pin. A resistor connected from pin 4 to ground sets the LED current. This pin is also used to dim the LEDs. 5 3 SHDN Shutdown pin. 6 2 VIN — 1 Power Ground Doc. No. 5001, Rev. AC Function Switch pin. This is the drain of the internal power switch. For minimum EMI, minimize the trace area connected to this pin. 2 Input supply pin. This pin should be bypassed with a capacitor to ground. A 4.7µF capacitor mounted close to the pin is recommended. Power Ground CAT32 ABSOLUTE MAXIMUM RATINGS These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground. VIN , LED, SHDN Voltage ....................................... 8V Lead Soldering Temperature (10 secs) ............ 300°C SW Voltage ........................................................... 20V Storage Temperature .......................... -65°C to 150°C RSET Voltage ......................................................... 1V ESD Rating - Human Body Model .................... 2000V Junction Temperature ....................................... 125°C RECOMMENDED OPERATING CONDITIONS Parameter Range Unit VIN 2 to 7 V Ambient Temperature Range -40 to +85 ° C Inductor L1 6.8 ±20% typical µH Input Capacitor C1 4.7 ±20% typical µF Output Capacitor C2 1.0 ±20% typical µF ILED with 1 to 4 LEDs in series 0 to 20 mA ELECTRICAL SPECIFICATIONS Over recommended operating conditions unless otherwise specified. TA = 25°C, VIN = 2V and VSHDN = 1.2V. Symbol Parameter Conditions IQ Quiescent Current IGND Typ Max Units VRSET = 0.2V 0.5 0.7 mA Ground Current in Shutdown VSHDN = 0V 0.05 1 µA VLED LED Pin Voltage VIN < VOUT, ILED =15mA 120 180 mV ILED LED Current Adjust Range 40 mA ILED Min 5 Programmed LED Current RSET = 562Ω 33 38 45 RSET = 750Ω 25 30 36 RSET = 1.5kΩ 12.5 15 17.5 RSET = 4.53kΩ 5 mA ILED LED Pin Current Temperature Coefficient ILED = 15mA -0.01 mA/° C VRSET RSET Pin Voltage RSET = 1.5kΩ 100 mV Shutdown Pin Logic High Level 0.85 V Shutdown Pin Logic Low Level 0.25 V fSW Boost Converter Frequency 0.8 1.2 1.6 MHz ISWL Switch Current Limit 400 550 780 mA 1.2 Ω Switch Resistance VIN = 2V, ISW = 100mA 0.7 RSW VIN = 3V, ISW = 100mA 0.5 0.9 Ω Switch Leakage Current Switch Off, VSW = 5V 0.01 5 µA Efficiency Components shown on Figure 1 83 3 % Doc No. 5001, Rev. AC CAT32 TYPICAL CHARACTERISTICS VIN=3.6V, TAMB=25˚C, CIN=4.7µF, COUT=1µF, L=6.8µH, unless otherwise specified. Quiescent Current vs. Input Voltage Quiescent Current vs. Temperature 600 . 600 VIN = 7V 500 500 400 400 300 300 200 VIN = 2V 200 2 3 4 5 6 7 -50 INPUT VOLTAGE [V] Switching Frequency vs. Input Voltage 0 25 50 75 100 125 Switching Frequency vs. Temperature 2.00 2.0 SWITCH FREQUENCY [MHz] SWITCH FREQUENCY [MHz] -25 1.60 1.20 0.80 0.40 0.00 1.6 1.2 0.8 0.4 0.0 2 3 4 5 6 7 -50 INPUT VOLTAGE [V] LED Current vs. Input Voltage -25 0 25 50 75 100 125 LED Current vs. Temperature 35 20 30 25 LED CURRENT [mA] LED CURRENT [mA] Rset = 750 Rset = 1.13k 20 Rset = 1.5k 15 Rset = 2.26k 10 5 0 2 3 Doc. No. 5001, Rev. AC 4 5 INPUT VOLTAGE [V] 6 15 10 5 0 7 -50 4 -25 0 25 50 75 100 125 CAT32 TYPICAL CHARACTERISTICS Switch Resistance vs. Input Voltage Switch Resistance vs. Temperature 1.0 1.0 SWITCH RESISTANCE [Ohm] . SWITCH RESISTANCE [Ohm] . VIN=3.6V,TAMB=25˚C, CIN=4.7µF, COUT=1µF, L=6.8µH, unless otherwise specified. 0.8 0.6 0.4 0.2 0.0 2 3 4 5 6 0.8 VIN = 3V 0.6 0.4 0.2 0.0 -50 -25 0 25 50 75 100 125 INPUT VOLTAGE [V] Vsw, IL, & Vout Signal Waveforms LED Pin Voltage vs. LED current 300 250 200 150 100 50 0 0 8 16 24 32 LED CURRENT [mA] 40 VIN = 3.7V with 15mA load through 4 LEDs Efficiency vs. Input Voltage PWM on SHDN pin Waveform EFFICIENCY (%) . 85 80 75 4 LEDs at 15mA Vout =13V 70 65 60 2 3 4 5 INPUT VOLTAGE [V] 6 5 Doc No. 5001, Rev. AC CAT32 OPERATION possible. A low LED pin voltage ensures high efficiency. The CAT32 device is a high efficiency, constant frequency, current regulating boost converter. Current through the internal power switch is continuously monitored cycle-by-cycle. If the current limit is exceeded, the switch is immediately turned off, protecting the device, for the remainder of the cycle. The device includes a switch and an internally compensated loop for the regulation of the LED current. Operation can be best understood by examining the block diagram. The RSET pin is regulated at 100mV and the current through the external resistor will set the regulated current in the LEDs (from 5mA to 40mA) with a multiplication factor of 225. PWM dimming operation can be achieved by switching the SHDN pin or by pulling the RSET pin higher than 0.1V. While maintaining LED current regulation, the CAT32 automatically adjusts the LED pin voltage to be as low as BLOCK DIAGRAM L1 C1 D1 1 Over Voltage Protection (22V) C2 SW 1.2 MHz Oscillator PWM & Logic + - Vin LED 3 ILED Current Sense Amp + CAT32 100mV 6 VIN 5 SHDN Current Control ILED = 225 x IS SOT23 Pin Numbers 225x GND 2 IS RSET 4 RSET Figure 2. CAT32 Block Diagram Doc. No. 5001, Rev. AC 6 CAT32 APPLICATION INFORMATION Inductor Selection and Efficiency Inductor vendors are shown below. Contact the manufacturer for detailed technical data and new product information. Table 1: Inductor Manufacturers Inductor L (µH) Maximum DCR (mΩ) Maximum Height (mm) ELJEA4R7 4.7 180 2.2 Panasonic ELJEA6R8 6.8 250 2.2 714.373.7334 LQH3C4R7M24, 4.7 260 2.2 10 300 2.2 770.436.1300 LB2016B4R7 4.7 250 2.0 Taiyo Yuden LB2016B100 3.8 350 2.0 408.573.4150 CMD4D06-4R7 4.7 216 0.8 CMD4D06-6R8 6.8 296 0.8 Sumida CLQ4D10-4R7 4.7 162 1.2 847.956.0666 CLQ4D10-6R8 6.8 195 1.2 LQH32CN4R7M11 LQH3C100K24, Vendor Web www.panasonic.com Murata www.murata.com LQH32CN100K11 www.t-yuden.com www.sumida.com CAPACITOR SELECTION Low ESR (equivalent series resistance) capacitors should be used at the output to minimize the output ripple voltage. The low ESR and small package options available with multilayer ceramic capacitors make them excellent choices. The X5R and X7R capacitor types are preferred because they retain their capacitance over wider voltage and temperature ranges than the Y5V or Z5U types. A 1.0µF or 2.2µF output capacitor is recommended for most applications. Low profile ceramic capacitors with a 1mm maximum height/thickness are available for designs height requirements. Ceramic capacitors also make a good choice for the input capacitor, which should be mounted as close as possible to the CAT32. A 2.2µF or 4.7µF input capacitor is recommended. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information as new products and package options are introduced regularly. The voltage rating of the output capacitor C2 depends on the number of LEDs driven in series. A 10V ceramic capacitor is recommended when driving two LEDs. A 16V ceramic capacitor is recommended when driving 3 or 4 LEDs. Table 2: Ceramic Capacitor Manufacturers Supplier Phone Web Taiyo Yuden 408.573.4150 www.t-yuden.com Murata 814.237.1431 www.murata.com Kemet 408.986.0424 www.kemet.com 7 Doc No. 5001, Rev. AC CAT32 DIODE SELECTION output voltage. The diode conducts current only when the power switch is turned off (typically less than onethird the time), so a 0.4A or 0.5A diode will be sufficient for most designs. Schottky diodes, with their low forward voltage drop and fast switching speed, are the ideal choice for high efficiency applications. Table 3 shows several different Schottky diodes that work well with the CAT32. Make sure that the diode has a voltage rating greater than the Table 3: Schottky Diode Suppliers Part Supplier MBR0520 ON Semiconductor MBR0530 www.onsemi.com MBR0540 800.282.9855 ZHCS400 Zetex LED CURRENT PROGRAMMING regulates the current into the LED pin, ILED, to 225 times the value of ISET. For the best accuracy, a 1% or better resistor is recommended. Table 4 shows several typical 1% RSET values. The LED current is programmed with a single resistor connected to the RSET pin The RSET pin is internally regulated to 100mV, which sets the current flowing out of this pin, ISET, equal to 100mV/RSET. The CAT32 Table 4: RSET Resistor Values ILED (mA) RSET 40 30 25 20 15 10 5 562Ω 750Ω 909Ω 1.13kΩ 1.50kΩ 2.26kΩ 4.53kΩ For other LED current values, use the following equation to choose RSET. 0.1V RSET = 225 × ILED 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. Doc. No. 5001, Rev. AC 8 CAT32 LED DIMMING WITH PWM SIGNAL PWM brightness control provides the widest dimming range (greater than 20:1). By turning 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 CAT32 can be accomplished two different ways. 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. Applications involving color LCDs can find the blue tint objectionable. 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 CAT32, reducing the total quiescent current to near zero. When a PWM control signal is used to drive the SHDN pin of the CAT32, 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. LED brightness varies linearly with the PWM duty cycle. 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 calculated (where VMAX is the “HIGH” value of the PWM signal): V RPWM = RSET × MAX − 1 0.15V LED DIMMING WITH A LOGIC SIGNAL RINCR determines how much LED current increases when the external NMOS switch is turned ON. For applications that need to adjust the LED brightness in discrete steps, a logic signal can be used. RMIN sets the minimum LED current value (when the NMOS is OFF): 0.1V RINCR = 225 × ILED(Increase) 0.1V RMIN = 225 × ILED(MIN) LED DIMMING WITH A DC VOLTAGE VMAX − 0.1V R ADJ = 225 × I LED(MAX ) −ILEAD(MIN) CAT32 CAT32 SHDN RSET 4 5 CAT32 CAT32 RSET 4 RPWM RSET 10kΩ RPWM RSET 4 RSET RADJ PWM PWM PWM CAT32 RSET 0.1µF 4 RINCR VDC RSET RMIN Figure 3: LED Dimming Circuits 9 Doc No. 5001, Rev. AC LOGIC SIGNAL CAT32 PCB LAYOUT GUIDELINES The CAT32 is a high-frequency switching regulator and therefore proper PCB board layout and component placement can minimize noise and radiation and increase efficiency. To maximize efficiency, the CAT32 design has fast switch rise and fall times. To prevent radiation and high frequency resonance problems minimize the length and area of all traces connected to the SW pin and use a ground plane under the switching regulator. The switch, schottky output diode and output capacitor signal path should be kept as short as possible. The ground connection for the RSET resistor should be tied directly to the GND pin and not be shared with other components. TYPICAL APPLICATION CIRCUITS The application diagrams below are shown for the SOT23 packages. Two LEDs with DC Level Dimming Control: D1 VIN 6 VIN 1 SW CAT32 5 2.5V DC DIMMING CONTROL SHDN LED RSET 4 GND 2 3 15mA Three LEDs with DC Level Dimming Control: Efficiency - Three LEDs D1 VIN 85 Vin = 4.2V 1 SW EFFICIENCY [%] 6 VIN CAT32 5 2.5V DC DIMMING CONTROL SHDN LED RSET 4 GND 2 3 15mA 80 Vin = 3.0V 75 70 65 60 0 5 10 15 LED CURRENT [mA] Doc. No. 5001, Rev. AC 10 20 CAT32 Efficiency - Four LEDs Four LEDs with PWM Dimming Control: D1 85 6 VIN PWM DIMMING CONTROL EFFICIENCY [%] VIN 1 SW CAT32 5 SHDN LED RSET 4 GND 2 3 Vin = 4.2V 80 Vin = 3.0V 75 70 65 15mA 60 0 5 10 15 LED CURRENT [mA] 11 Doc No. 5001, Rev. AC 20 CAT32 PACKAGE OUTLINES 6 LEAD SOT-23 (AA OPTION) 3 4 aaa C 2X D H e1 A B D 5 N/2 +1 N B VIEW A-A SEE VIEW C E/2 E1/2 3 R1 E1 4 E R GAUGE PLANE L2 aaa C D L SEATING C PLANE 2X (L1) 1 2 N/2 bbb C 2X N/2 TIPS e 5 B NX b ddd M VIEW C (b) WITH METAL b1 CA BD c c1 BASE METAL SECTION B - B b 5 8 7 A 5 e/2 X X=A &/or B A X X=A &/or B ODD LEAD SIDES TOP VIEW A2 ccc C NX A1 EVEN LEAD SIDES TOP VIEW SEATING C PLANE A All Dimensions are in Millimeters Min Notes Tolerances of Form and Position Notes — — 1.00 aaa 0.15 1,2 A1 0.01 0.05 0.10 bbb 0.25 1,2 ccc 0.10 A2 0.84 0.87 0.90 c 0.12 0.15 0.20 c1 0.08 0.13 0.16 1,2 7 Variations 7 AA BA 2.90BSC E 2.80BSC 3,4 b 0.30 — 0.45 0.30 — 0.45 0.22 E1 1.60BSC 3,4 b1 0.31 0.35 0.39 0.31 0.35 0.39 0.22 0.30 0.40 3,4 6 AB D L1 0.50 0.60REF L2 0.25BSC R 0.10 — — R1 0.10 — 0.25 0° 4° 8° θ 5. 6. 7. 8. Max A L 4. Nom Min Nom Max Min Nom Max Min Nom Max Notes — 0.36 7,8 0.26 0.30 e 0.95BSC 0.95BSC 0.65BSC e1 1.90BSC 1.90BSC 1.95BSC N 6 5 8 Tolerances of Form and Position ddd 0.20 0.20 0.13 1,2 Notes: 1. Dimensions and tolerancing per ASME Y14.5M - 1994 2. Dimension are in mm. θ1 4° 10° 12° 3. Dimension D does not include mold flash, protrusions or gate burrs. Mold flash, protrusions or gate burrs shall not exceed 0.15mm per end. Dimension E1 does not include interlead flash or protrusion. Interlead flash or protrusion shall not exceed 0.15mm per side. D and E1 dimensions are determined at Datum H. The package top may be smaller than the package bottom. Dimensions D and E1 are determined at the outermost extremes of the plastic body exclusive of mold flash, the bar burrs, gate burrs and interlead flash, but including any mismatch between the top and bottom of the plastic body. D and E1 dimensions are determined at Datum H. Datums A & B to be determined at Datum H. Package varation "AB" is a 5 lead version of the 6 lead variation "AA" where lead #5 has been removed from the 6 lead "AA" variation. These dimensions apply to the flat section of the lead between 0.08mm and 0.15mm from the lead tip. Dimension "b" does not include dambar protrusion. Allowable dambar protrusion shall be 0.08mm total in excess of the "b" dimension at maximum material condition. The dambar cannot be located on the lower radius of the foot. Minimum space between protrusion and an adjacent lead shall not be less than 0.07mm. Doc. No. 5001, Rev. AC 12 CAT32 TDFN 3X3 PACKAGE (RD4) 5 0.75 + 0.05 A B 3.00 + 0.10 (S) 8 2X 1 3.00 + 0.10 (S) 4 0.15 C 2X 0.0 - 0.05 0.15 C PIN 1 INDEX AREA 5 8 1.50 + 0.10 0.75 + 0.05 C 2.30 + 0.10 C0.35 0.25 min. PIN 1 ID 1 0.30 + 0.07 (8x) 0.30 + 0.10 (8x) 0.65 TYP. (6x) 1.95 REF. (2x) NOTE: 1. ALL DIMENSION ARE IN mm. ANGLES IN DEGREES. 2. COPLANARITY SHALL NOT EXCEED 0.08 mm. 3. WARPAGE SHALL NOT EXCEED 0.10 mm. 4. PACKAGE LENGTH / PACKAGE WIDTH ARE CONSIDERED AS SPECIAL CHARACTERISTIC(S) 5. REFER JEDEC MO-229 / WEEC 13 Doc No. 5001, Rev. AC CAT32 REVISION HISTORY Date Rev. Reason 10/9/2003 AA Revised Typical Characteristics plots 2/11/2004 AB Revised Efficiency plots 11/1/2004 AC Added Green package designation Eliminated TDFN (3x4.9mm) package Copyrights, Trademarks and Patents Trademarks and registered trademarks of Catalyst Semiconductor include each of the following: DPP ™ AE2 ™ Catalyst Semiconductor has been issued U.S. and foreign patents and has patent applications pending that protect its products. For a complete list of patents issued to Catalyst Semiconductor contact the Company’s corporate office at 408.542.1000. CATALYST SEMICONDUCTOR MAKES NO WARRANTY, REPRESENTATION OR GUARANTEE, EXPRESS OR IMPLIED, REGARDING THE SUITABILITY OF ITS PRODUCTS FOR ANY PARTICULAR PURPOSE, NOR THAT THE USE OF ITS PRODUCTS WILL NOT INFRINGE ITS INTELLECTUAL PROPERTY RIGHTS OR THE RIGHTS OF THIRD PARTIES WITH RESPECT TO ANY PARTICULAR USE OR APPLICATION AND SPECIFICALLY DISCLAIMS ANY AND ALL LIABILITY ARISING OUT OF ANY SUCH USE OR APPLICATION, INCLUDING BUT NOT LIMITED TO, CONSEQUENTIAL OR INCIDENTAL DAMAGES. Catalyst Semiconductor products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Catalyst Semiconductor product could create a situation where personal injury or death may occur. Catalyst Semiconductor reserves the right to make changes to or discontinue any product or service described herein without notice. Products with data sheets labeled "Advance Information" or "Preliminary" and other products described herein may not be in production or offered for sale. Catalyst Semiconductor advises customers to obtain the current version of the relevant product information before placing orders. Circuit diagrams illustrate typical semiconductor applications and may not be complete. Catalyst Semiconductor, Inc. Corporate Headquarters 1250 Borregas Avenue Sunnyvale, CA 94089 Phone: 408.542.1000 Fax: 408.542.1200 www.catalyst-semiconductor.com Doc. No. 5001, Rev. AC Publication #: Revison: Issue date: Type: 14 5001 AC 11/1/04 Preliminary