MP3302 40V, 1.3A, Single-cell Step-up White LED Driver with Single Wire Dimming Control The Future of Analog IC Technology DESCRIPTION FEATURES The MP3302 is a step-up converter designed for driving arrays of WLEDS from a single cell Lithium Ion battery. The MP3302 uses current mode, fixed frequency architecture to regulate the LED current, which is measured through an external current sense resistor. Its low 200mV feedback voltage reduces power loss and improves efficiency. The MP3302 is turned off if an over-voltage condition is present due to an open circuit condition. • • • • • • • • • • The MP3302 includes under-voltage lockout, current limiting and thermal overload protection preventing damage in the event of an output overload. Internal Power MOSFET Drives up to 10 Series White LEDs Up to 87% Efficiency Single Wire Dimming Control 1.3MHz Fixed Switching Frequency Open Load Shutdown Low 200mV Feedback Voltage UVLO, Thermal Shutdown Internal 1.3A Current Limit Available in TSOT23-5 and 2mm x 3mm QFN8 Packages APPLICATIONS • • • • The MP3302 is available in small 5-pin TSOT23 and 8-pin QFN (2mm x 3mm) packages. 5” ~ 7” LCD Panels Handheld Computers and PDAs Digital Still Cameras Small LCD Displays “Monolithic Power Systems”, “MPS”, and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION String 1 ... String 9 VIN 3.3V - 6V 95 EN SW MP3302 GND FB LED1 LED25 LED2 LED26 LED3 LED27 3 WLEDs,9 Strings 90 EFFICIENCY (%) IN Enable/ Dimming Control Efficiency vs Input Voltage 85 80 75 70 65 60 MP3302 Rev. 0.98 5/5/2010 3 4 5 6 INPUT VOLTAGE(V) www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 1 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL ORDERING INFORMATION Part Number MP3302DJ* MP3302DD** Package TSOT23-5 QFN8 (2mm x 3mm) Top Marking N6 N7 Free Air Temperature (TA) –40°C to +85°C –40°C to +85°C * For Tape & Reel, add suffix –Z (e.g. MP3302DJ–Z); For RoHS Compliant Packaging, add suffix –LF (e.g. MP3302DJ–LF–Z). ** For Tape & Reel, add suffix –Z (e.g. MP3302DD–Z); For RoHS Compliant Packaging, add suffix –LF (e.g. MP3302DD–LF–Z) PACKAGE REFERENCE TOP VIEW TOP VIEW SW 1 GND 2 FB 3 5 4 IN EN GND 1 8 SW IN 2 7 NC NC 3 6 FB EN 4 5 GND Exposed Pad Connect to GND TSOT23-5 QFN8 (2mm x 3mm) ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance SW Pin.........................................–0.5V to +44V All Other Pins ..............................–0.3V to +6.5V Continuous Power Dissipation…(TA = +25°C) (2) TSOT23-5 ................................................ 0.57W QFN8 (2mm x 3mm) ................................ 1.56W Storage Temperature.............. –55°C to +150°C TSOT23-5.............................. 220 .... 110.. °C/W QFN8 (2mm x 3mm) ............... 80 ...... 16... °C/W Recommended Operating Conditions (3) IN Supply Voltage ..............................2.5V to 6V SW Pin ................................................VIN to 36V Operating Junction Temp. (TJ)..... –40°C to +125°C MP3302 Rev. 0.98 5/5/2010 (4) θJA θJC Notes: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = (TJ (MAX)-TA)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 3) The device is not guaranteed to function outside of its operating conditions. 4) Measured on approximately 1” square of 1 oz copper. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 2 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL ELECTRICAL CHARACTERISTICS VIN = VEN = 5V, TA = +25°C, unless otherwise noted. Parameters Symbol Operating Input Voltage Supply Current (Shutdown) Supply Current (Quiescent) Switching Frequency Maximum Duty Cycle Under Voltage Lockout IN Under Voltage Lockout Under Voltage Lockout Hysteresis Open Lamp Shutdown Threshold Enable EN OFF Threshold EN ON Threshold Minimum EN Dimming Threshold Maximum EN Dimming Threshold Feedback FB Voltage FB Input Bias Current Output Switch SW On-Resistance (5) SW Current Limit (5) Thermal Shutdown Condition VIN Min Max Units 4 690 1.3 6 8 850 1.5 V µA µA MHz % 2.25 2.45 V 2.5 VEN = 0V VFB = 0.15V fSW VFB = 0V UVLO Typ 1.0 92 VIN Rising 92 VOV VOV Rising 40 VEN Falling VEN Rising 0.4 42 mV 44 V 0.6 V V VFB = 0V 0.655 0.7 0.845 V VFB = 0.2V 1.275 1.4 1.425 V VEN = 1.5V VFB = 0.1V 185 -600 200 -300 215 mV nA RON Duty Cycle = 60% (5) 0.5 1.33 Ω A 150 °C Notes: 5) Guaranteed by design. MP3302 Rev. 0.98 5/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 3 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL PIN FUNCTIONS TSOT23-5 Pin # QFN8 Pin # Name 1 8 SW 2 1, 5 3 6 4 4 5 2 3 MP3302 Rev. 0.98 5/5/2010 Pin Function Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the power inductor and output rectifier to SW. SW can swing between GND and 36V. GND, Exposed Ground. Connect exposed pad to GND plane for proper thermal performance. Pad Feedback Input. The MP3302 regulates the voltage across the current sense resistor between FB and GND. Connect a current sense resistor from the FB bottom of the LED string to GND. Connect the bottom of the LED string to FB. The regulation voltage is 200mV. ON/OFF Control and Dimming Command Input. A voltage greater than 0.6V will turn the part on and less than 0.4V will turn the part off. If the EN pin EN voltage is between 0.7V and 1.4V, VFB is regulated between 0V and 200mV. To use PWM dimming, apply a 200Hz to 1KHz square wave signal with amplitude greater than 1.5V to this pin. IN Input Supply Pin. Must be locally bypassed. NC No Connect. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 4 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL TYPICAL PERFORMANCE CHARACTERISTICS VIN = 5V, 3WLEDs 9Strings, unless otherwise noted. Efficiency vs Input Voltage Steady State Operation Enable Startup VIN = 5V, 3 WLEDs,9 Strings VIN = 5V, 3 WLEDs,9 Strings 95 3 WLEDs,9 Strings EFFICIENCY (%) 90 85 6 WLEDs 80 75 8 WLEDs 70 60 3 VSW 10V/div. VEN 2V/div. VOUT 5V/div. Iinductor 500mA/div. 10WLEDs 65 VSW 10V/div. VFB 50mV/div. VOUT AC Coupled 100mV/div. ILED 100mA/div. 4 5 6 INPUT VOLTAGE(V) 400ns/div. Enable Shutdown Start Up into Openload PWM Dimming VIN = 5V, 3 WLEDs,9 Strings VIN = 5V VIN = 5V, 3 WLEDs,9 Strings VSW 10V/div. VSW 10V/div. VEN 2V/div. VSW 20V/div. VOUT 5V/div. VEN 5V/div. VEN 5V/div. ILED 100mA/div. VOUT 5V/div. VOUT 20V/div. Output Current vs Analog Dimming Voltage Output Current vs PWM Dimming Duty VIN=5V, 3 WLEDs, 9 Strings VIN=5V, 3 WLEDs, 9 Strings f=1kHz 200 180 160 140 120 100 80 60 40 20 180 160 140 120 100 80 60 40 20 0 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 EN PIN VOLTAGE (V) MP3302 Rev. 0.98 5/5/2010 200 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) ILED 100mA/div. 0 0 0.2 0.4 0.8 PWM DIMMING DUTY 1 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 5 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL OPERATION The MP3302 uses a constant frequency, peak current mode boost regulator architecture to regulate the series string of white LEDs. The operation of the MP3302 can be understood by referring to the block diagram of Figure 1. The voltage at the output of the error amplifier is an amplified version of the difference between the 200mV reference voltage and the feedback voltage. In this way the peak current level keeps the output in regulation. At the start of each oscillator cycle the FET is turned on through the control circuitry. To prevent sub-harmonic oscillations at duty cycles greater than 50 percent, a stabilizing ramp is added to the output of the current sense amplifier and the result is fed into the positive input of the PWM comparator. When this voltage equals the output voltage of the error amplifier the power FET is turned off. If the feedback voltage starts to drop, the output of the error amplifier increases. This results in more current flowing through the power FET, thus increasing the power delivered to the output. - FB + + CONTROL LOGIC M1 SW AMPLIFIER PWM COMPARATOR 200mV for Full Brightness + ENABLE & DIMMING CONTROL EN Enable + - GND CURRENT SENSE AMPLIFIER 1.3MHz OSC Figure 1—Functional Block Diagram MP3302 Rev. 0.98 5/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 6 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL APPLICATION INFORMATION VIN 3.3V to 6V 4.7uH MBR0520 C1 10uF IN Enable/ Dimming Control EN C2 0.47uF SW MP3302 GND FB Figure 2—Circuit for Driving 9 Strings of 3 WLEDs A typical application circuit can be seen in Figure 2. The 9 strings of 3 white LEDs can be driven from a voltage supply range of 3.3V to 6V at an output current of 180mA. A 0.47µF output capacitor is sufficient for most applications. A 4.7µH inductor with low DCR (Inductor DC resistance) is recommended to improve efficiency. A 10µF ceramic capacitor is recommended for the input capacitance in the real system. Schottky diodes have fast recovery and a low forward voltage and are recommended. Schottky diodes rated with 500mA are sufficient for the MP3302. The MP3302 has internal soft-start to limit the amount of current through VIN at startup and to also limit the amount of overshoot on the output. Setting the LED Current The LED current is controlled by the feedback resistor, R1. The current through the LEDs is given by the equation 200mV/R1. Table 1 shows the selection of resistors for a given LED current. Table 1—ILED vs. R1 ILED (mA) 1 5 10 20 60 180 R1 (Ω) 200 40 20 10 3.33 1.11 The ramped voltage that is added to the current sense amplifier reduces the current output as the duty cycle increases. As more LEDs are added, the output voltage rises but the current that can be delivered to the load is reduced as well. MP3302 Rev. 0.98 5/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 7 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL LED Current Programming Applying a DC voltage between 0.7V and 1.4V to EN pin programs a feedback voltage between 0V and 200mV. Thus the analog dimming of LED current can be achieved. The DC dimming voltage must be locally bypassed to prevent noise interfering with the feedback reference level. PWM Dimming Apply a 200Hz to 1kHz square waveform to the EN pin to implement PWM dimming of the LEDs. The minimum recommended amplitude of the PWM signal is 1.5V. For high frequency PWM dimming (>1kHz), it is also recommended that the dimming control be implemented as shown in Figure 3. The cut off frequency of the RC filter should be 10 times lower than that of the input PWM signal. For example, when the PWM frequency is 20kHz, a 20kΩ resistor and 100nF capacitor can be used. The DC voltage on EN pin is then equal to the PWM high level voltage multiplies the PWM duty. The DC voltage from 0.7V to 1.4V programs the output current from 0~100%. Open Load Protection Open Load protection will shut off the MP3302 if the output voltage goes too high. In some cases an LED may fail, this will result in the feedback voltage always being zero. The part will run at maximum duty cycle boosting the output voltage higher and higher. If the output ever exceeds 42V, the MP3302 will shut down. The part will not switch again until the power is recycled. Layout Considerations Careful attention must be paid to the PCB board layout and components placement. Proper layout of the high frequency switching path is critical to prevent noise and electromagnetic interference problems. The current loop of IC, output diode, and output capacitor should be as short as possible. The IN pin of the IC must be locally bypassed. A RC filter is highly recommended for eliminating the noise on IN pin. It could be implemented as shown in Figure 4. Input LED1 SW IN MP3302 LED2 GND LED3 MP3302 PWM EN FB Figure 4—Input Bias Filtering Figure 3—High Frequency PWM Dimming Control MP3302 Rev. 0.98 5/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 8 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL TYPICAL APPLICATION CIRCUITS D1 B0540 L1 VIN 3.3V -18V 4.7uH/1A C1 4.7uF 16V Optional Bias Circuit C3 0.1uF 50V 2 4 LED+ 8 IN EN SW LEDD2 5.6V ZENER MP3302 EN C4 330nF 50V FB GND 6 GND 1 Figure 5 — Driving 27 WLEDs (9 WLEDs in Series and 3 Strings Paralleled) with 3.3V―18V Input Voltage In order to improve the MOSFET on-resistance at low input voltage and make the chip compatible for high input voltage, the additional bias circuit should be used. C5 L1 VIN 4.5V-16V 4.7uH/1A C1 4.7uF 16V 2.2uF/25V L2 4.7uH/1A Q2 2N3904 D2 5.6V ZENER C3 0.1uF 25V D1 B0530 C4 0.47uF 25V LED+ LED- 2 8 IN SW Required Bias Circuit for High Input Voltage EN 4 MP3302 EN FB GND 6 GND 1 Figure 6 — Wide Input Voltage Sepic Converter for 27 WLEDs ( 3 WLEDs in Series and 9 Strings Paralleled ) MP3302 Rev. 0.98 5/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 9 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL L1 VIN 3V-6V D1 C1 B0540 R2 16V LED1 LED2 2 C2 IN 16V 8 LED3 SW LED4 MP3302 4 EN 1 GND LED5 EN FB GND C3 LED6 6 LED7 LED8 LED9 LED10 R1 1% Figure 7 — Driving 10 WLEDs in Series with 3V—6V Input Voltage D1 B0530F L1 VIN A C1 C2 16V 16V D2 ZENER DIODE C3 25V 2 IN 4 EN EN WLED+ 8 C4 SW 50V MP3302 FB GND GND WLED- 6 R1 1 Figure 8 — Driving 27 WLEDs (3 WLEDs in Series and 9 Strings) with 3 V Input Voltage MP3302 Rev. 0.98 5/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 10 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL PACKAGE INFORMATION TSOT23-5 0.95 BSC 0.60 TYP 2.80 3.00 5 4 1.20 TYP 1.50 1.70 1 2.60 TYP 2.60 3.00 3 TOP VIEW RECOMMENDED LAND PATTERN 0.84 0.90 1.00 MAX 0.09 0.20 SEATING PLANE 0.30 0.50 0.95 BSC 0.00 0.10 SEE DETAIL "A" FRONT VIEW SIDE VIEW NOTE: GAUGE PLANE 0.25 BSC 0.30 0.50 0o-8o DETAIL “A” MP3302 Rev. 0.98 5/5/2010 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSION OR GATE BURR. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.10 MILLIMETERS MAX. 5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AA. 6) DRAWING IS NOT TO SCALE. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 11 MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL QFN8 (2mm x 3mm) 2.90 3.10 PIN 1 ID MARKING 0.30 0.50 0.18 0.30 1.90 2.10 PIN 1 ID INDEX AREA 1.65 1.85 8 PIN 1 ID SEE DETAIL A 1 1.50 1.70 0.50 BSC 4 5 TOP VIEW BOTTOM VIEW PIN 1 ID OPTION A 0.30x45” TYP. 0.80 1.00 PIN 1 ID OPTION B R0.20 TYP. 0.20 REF 0.00 0.05 SIDE VIEW DETAIL A 2.90 0.70 NOTE: 1.70 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH. 3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX. 4) DRAWING CONFORMS TO JEDEC MO-229, VARIATION VCED-2. 5) DRAWING IS NOT TO SCALE. 0.25 1.60 0.50 RECOMMENDED LAND PATTERN NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MP3302 Rev. 0.98 5/5/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 12