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MP3302 40V, 1.3A, Single-cell Step-up White LED Driver with Single Wire Dimming Control Internal Power MOSFET FEATURES • • 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 • 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. The Future of Analog IC Technology reduces power DESCRIPTION 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 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. The MP3302 is available in small 5-pin TSOT23 and 8-pin QFN (2mm x 3mm) packages. TYPICAL APPLICATION VIN 3.3V - 6V Enable/ Dimming Control String 1 ... String 9 LED1 LED2 LED3 SW IN EN MP3302 GND FB LED25 LED26 LED27 Efficiency vs Input Voltage 3 WLEDs,9 Strings 3 4 5 INPUT VOLTAGE(V) ) % ( I Y C N E C F F E I 95 90 85 80 75 70 65 60 1 6 MP3302 Rev. 0.98 5/5/2010 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. www.MonolithicPower.com © 2010 MPS. All Rights Reserved.

MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL Part Number MP3302DJ* MP3302DD** ORDERING INFORMATION Package Top Marking TSOT23-5 N6 N7 QFN8 (2mm x 3mm) 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 SW GND FB 1 2 3 5 IN 4 EN TSOT23-5 ABSOLUTE MAXIMUM RATINGS (1) 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 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 TOP VIEW GND IN NC EN 1 2 3 4 8 7 6 5 SW NC FB GND Exposed Pad Connect to GND QFN8 (2mm x 3mm) Thermal Resistance (4) TSOT23-5.............................. 220.... 110.. °C/W QFN8 (2mm x 3mm)............... 80...... 16... °C/W θJC θJA 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-to- ambient 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 from permanent damage. the device 3) The device is not guaranteed to function outside of its operating conditions. 4) Measured on approximately 1” square of 1 oz copper. MP3302 Rev. 0.98 5/5/2010 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. www.MonolithicPower.com © 2010 MPS. All Rights Reserved. 2

MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL Typ Max Units V 6 µA 8 850 µA 1.5 MHz % 4 690 1.3 Min 2.5 1.0 92 40 0.4 UVLO VIN fSW VIN Rising VEN = 0V VFB = 0.15V VFB = 0V ELECTRICAL CHARACTERISTICS VIN = VEN = 5V, TA = +25°C, unless otherwise noted. Parameters Symbol Condition 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 (5) Notes: 5) Guaranteed by design. VEN Falling VEN Rising VFB = 0V VEN = 1.5V VFB = 0.1V VFB = 0.2V VOV Rising VOV RON Duty Cycle = 60% 2.25 2.45 92 42 44 0.6 0.655 0.7 0.845 1.275 1.4 1.425 185 -600 200 -300 215 0.5 1.33 150 V mV V V V V V mV nA Ω A °C 3 MP3302 Rev. 0.98 5/5/2010 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. www.MonolithicPower.com © 2010 MPS. All Rights Reserved.

MP3302 –40V, 1.3A, SINGLE-CELL STEP-UP WHITE LED DRIVER WITH SINGLE WIRE DIMMING CONTROL PIN FUNCTIONS TSOT23-5 QFN8 Pin # Pin # Name Pin Function 1 2 3 4 5 MP3302 Rev. 0.98 5/5/2010 8 SW 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 Pad Ground. Connect exposed pad to GND plane for proper thermal performance. Feedback Input. The MP3302 regulates the voltage across the current sense resistor between FB and GND. Connect a current sense resistor from the 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 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. Input Supply Pin. Must be locally bypassed. No Connect. FB EN IN NC 1, 5 6 4 2 3 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. www.MonolithicPower.com © 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 VSW 10V/div. VFB 50mV/div. VOUT AC Coupled 100mV/div. Iinductor 500mA/div. VSW 10V/div. VEN 2V/div. VOUT 5V/div. ILED 100mA/div. 3 WLEDs,9 Strings 6 WLEDs 8 WLEDs ) % ( I Y C N E C F F E I 95 90 85 80 75 70 65 60 3 10WLEDs 4 5 6 400ns/div. INPUT VOLTAGE(V) 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. VEN 2V/div. VOUT 5V/div. ILED 100mA/div. Output Current vs Analog Dimming Voltage VIN=5V, 3 WLEDs, 9 Strings ) A m ( T N E R R U C T U P T U O 200 180 160 140 120 100 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) VSW 20V/div. VEN 5V/div. VOUT 20V/div. ) A m ( T N E R R U C T U P T U O 200 180 160 140 120 100 80 60 40 20 0 Output Current vs PWM Dimming Duty VIN=5V, 3 WLEDs, 9 Strings f=1kHz 0 0.4 0.2 PWM DIMMING DUTY 0.8 VSW 10V/div. VEN 5V/div. VOUT 5V/div. ILED 100mA/div. 1 MP3302 Rev. 0.98 5/5/2010 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. www.MonolithicPower.com © 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. 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. FB EN - + AMPLIFIER 200mV for Full Brightness - + PWM COMPARATOR ENABLE & DIMMING CONTROL + Enable 1.3MHz OSC 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. 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. CONTROL LOGIC M1 SW + - CURRENT SENSE AMPLIFIER Figure 1—Functional Block Diagram MP3302 Rev. 0.98 5/5/2010 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. www.MonolithicPower.com © 2010 MPS. All Rights Reserved. GND 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 Enable/ Dimming Control IN EN GND MP3302 SW FB C2 0.47uF Figure 2—Circuit for Driving 9 Strings of 3 WLEDs low is sufficient capacitor 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 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 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. 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. forward 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 MP3302 Rev. 0.98 5/5/2010 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. www.MonolithicPower.com © 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%. LED1 LED2 LED3 PWM MP3302 EN FB 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 to prevent noise and path 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 for eliminating the noise on IN pin. It could be implemented as shown in Figure 4. recommended is critical filter is highly Input IN SW MP3302 GND Figure 4—Input Bias Filtering Figure 3—High Frequency PWM Dimming Control MP3302 Rev. 0.98 5/5/2010 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. www.MonolithicPower.com © 2010 MPS. All Rights Reserved. 8

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