MP3202DG-LF-Z

MP3202 1.3A Fixed Frequency White LED Driver The Future of Analog IC Technology DESCRIPTION FEATURES The MP3202 is a step-up converter designed for driving up to 39 white LEDs (13 strings of 3 LEDs each) from a 5V system rail. The MP3202 uses a current mode, fixed frequency architecture to regulate the LED current, which is measured through an external current sense resistor. Its low 104mV feedback voltage reduces power loss and improves efficiency. The OV pin monitors the output voltage and turns off the converter if an over-voltage condition is present due to an open circuit condition. • • • • • • • • • • • The MP3202 includes under-voltage lockout, current limiting and thermal overload protection preventing damage in the event of an output overload. The MP3202 is available in small 6-pin TSOT23 or 8-pin QFN (2mm x 2mm) packages. 2.5V to 6V Input Voltage Range On Board Power MOSFET Drives up to 39 White LEDs at 5V Input Up to 92% Efficiency Over 1MHz Fixed Switching Frequency Open Load Shutdown Low 104mV Feedback Voltage Soft-Start/PWM Dimming UVLO, Thermal Shutdown Internal 1.3A Current Limit Available in TSOT23-6 and QFN8 Packages APPLICATIONS • • • • Cell Phones Handheld Computers and PDAs Digital Still Cameras Small LCD Displays “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION Efficiency vs Input Voltage VIN 4.5V - 6V 100 IOUT=100mA IN EN EN SW MP3202 GND OV FB EFFICIENCY (%) 13 Strings 90 IOUT=180mA 80 70 60 50 4.0 MP3202 Rev. 0.91 9/21/2007 4.5 5.0 5.5 INPUT VOLTAGE (V) www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 6.0 1 MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER PACKAGE REFERENCE TOP VIEW TOP VIEW SW 1 6 IN GND 2 5 OV FB * 3 4 EN GND 1 8 SW IN 2 7 NC OV 3 6 FB EN 4 5 GND Part Number* Package Temperature Part Number** MP3202DJ TSOT23-6 –40°C to +85°C MP3202DG Package Temperature QFN8 –40°C to +85°C (2mm x 2mm) ** For Tape & Reel, add suffix –Z (eg. MP3202DG–Z) For Tape & Reel, add suffix –Z (eg. MP3202DJ–Z) For RoHS compliant packaging, add suffix –LF (eg. MP3202DJ–LF–Z) For RoHS compliant packaging, add suffix –LF (eg. MP3202DG–LF–Z) ABSOLUTE MAXIMUM RATINGS (1) SW Pin......................................–0.5V to +28.5V All Other Pins ..............................–0.3V to +6.5V Storage Temperature.............. –55°C to +150°C Recommended Operating Conditions (2) IN Supply Voltage ..............................2.5V to 6V Output Voltage ....................................VIN to 25V Operating Temperature............. –40°C to +85°C Thermal Resistance (3) θJA θJC TSOT23-6.............................. 220 .... 110.. °C/W QFN8 (2mm x 2mm) ............... 80 ...... 16... °C/W Notes: 1) Exceeding these ratings may damage the device. 2) The device is not guaranteed to function outside of its operating conditions. 3) Measured on approximately 1” square of 1 oz copper. 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 MP3202 Rev. 0.91 9/21/2007 VIN Min 2.5 VEN = 0V VFB = 0.15V fSW VFB = 0V UVLO VOV Typ 1.0 85 VIN Rising VOV Rising www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 0.1 690 1.3 92 2.25 Max Units 6 1 750 1.5 V µA µA MHz % 2.45 V 92 mV 28 V 2 MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER ELECTRICAL CHARACTERISTICS (continued) VIN = VEN = 5V, TA = +25°C, unless otherwise noted. Parameters Symbol Condition Enable EN Threshold EN Threshold EN Hysteresis EN Input Bias Current Feedback FB Voltage FB Input Bias Current Output Switch SW On-Resistance (4) SW Current Limit (4) VEN Rising, VIN = 5V VEN Rising, VIN = 2.5V Min Typ Max Units 1.0 0.8 1.35 1.6 V V mV µA 90 VEN = 0V, 5V VFB = 0.1V 1 94 –600 RON Duty Cycle = 60% Thermal Shutdown (4) 104 –300 114 mV nA 0.5 1.33 Ω A 160 °C Notes: 4) Guaranteed by design. PIN FUNCTIONS TSOT23-6 Pin # QFN8 Pin # 1 8 SW 2 1, 5 GND 3 6 FB 4 4 EN 5 3 OV 6 2 7 IN NC MP3202 Rev. 0.91 9/21/2007 Name Description 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 25V. Ground. Feedback Input. The MP3202 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 104mV. Regulator On/Off Control Input. A high input at EN turns on the converter, and a low input turns it off. When not used, connect EN to the input source for automatic startup. The EN pin cannot be left floating. Over Voltage Input. OV measures the output voltage for open circuit protection. Connect OV to the output at the top of the LED string. Input Supply Pin. Must be locally bypassed. No Connect. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 3 MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER OPERATION The MP3202 uses a constant frequency, peak current mode boost regulator architecture to regulate the strings of white LEDs. Refer to the block diagram in Figure 1 for details. 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%, 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 The voltage at the output of the error amplifier is an amplified version of the difference between the 104mV 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. + + AMPLIFIER CONTROL LOGIC M1 SW PWM COMPARATOR 104mV + + GND CURRENT SENSE AMPLIFIER 1.3MHz OSC Figure 1—Functional Block Diagram MP3202 Rev. 0.91 9/21/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 4 MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER APPLICATION INFORMATION VIN 4V to 6V MBR0520 IN OFF ON EN 9 Strings Total SW MP3202 GND OV FB Figure 2—Circuit for Driving 27 WLEDs A typical application circuit is provided in Figure 2. The 27 white LEDs can be driven from a voltage supply range of 4V to 6V at a total output current of 180mA. A 2.2µF output capacitor is sufficient for most applications but up to 1µF may be used. A 10µH inductor with low DCR (inductor resistance) is recommended to improve efficiency. A 4.7µF ceramic capacitor is recommended for the input capacitance in the real system. Schottky diodes with fast recovery and a low forward voltage are recommended. Schottky diodes with a 500mA rating are sufficient for the MP3202. The switching characteristics during normal operation can be seen in Figure 3. The MP3202 has internal soft-start to limit the amount of current through the IN pin at startup and to also limit the amount of overshoot on the output. The current limit is increased by a fourth every 40µs giving a total soft-start time of 120µs. MP3202 Rev. 0.91 9/21/2007 Steady State Operation VIN = 5V, 27 LEDS, 180mA VSW 5V/div. VOUT AC 200mV/div. IL 500mA/div. 400ns/div. Figure 3—Steady State Operation Figure 4 shows the startup behavior of the MP3202. The ramped voltage 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. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 5 MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER Startup Waveforms VIN = 5V, 27 LEDs, 180mA VEN 5V/div. VOUT 5V/div. IOUT 200mA/div. IL 500mA/div. Figure 4—Startup Waveforms Analog and Digital Dimming There are three methods to control dimming for the MP3202 during normal operation. The first method uses DC voltage to control the feedback voltage. This is shown in Figure 6. As the DC voltage increases, current starts flowing down R1, R2 and R3. The loop will continue to regulate the feedback voltage to 104mV. Thus the current has to decrease through the LEDs by the same amount of current as is being injected from the DC voltage source. With a VDC from 0V to 2V, the resistor values shown for R2 and R3 can control the LED current from 0mA to 20mA. VDC Figure 5 shows the dependence on current limit versus duty cycle. LED1 1.6 CURRENT LIMIT (A) 1.5 LED2 1.4 1.3 LED3 MP3202 1.2 FB 1.1 1.0 0.9 0.8 0 20 40 60 80 DUTY CYCLE (%) 100 Figure 6—Dimming Control Using a DC Voltage Figure 5—Current Limit vs. Duty Cycle Setting the LED Current The LED current is controlled by the feedback resistors R1 and R2, as shown in Figure 2. The current through the LEDs is given by the equation: ILED = 104mV × R1 + R2 R1 × R2 Table 1 shows the selection of resistors for a given LED current. Table 1—ILED vs. R1 ILED (mA) 10 50 100 150 180 MP3202 Rev. 0.91 9/21/2007 R1 (Ω) 10.4 2.08 1.04 1.5 1.2 R2 (Ω) N/A N/A N/A 1.3 1.1 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 6 MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER Other applications require a logic signal to control dimming. This is shown in Figure 7. The PWM signal is applied to the EN pin of the MP3202. The LEDs will switch between full load to completely shut off. The average current through the LEDs will increase proportionally to the duty cycle of the PWM signal. The PWM signal used in Figure 7 should be 1KHz or below due to the soft-start function. LED1 LED2 LED3 MP3202 PWM EN Open Load Protection Open Load protection will shut off the MP3202 if the output voltage rises too high when the OV pin is tied to the output. In some cases an LED may fail. This will result in the feedback voltage always remaining at zero. The part will run at maximum duty cycle boosting the output voltage higher and higher. By tying the OV pin to the top of the LED string the MP3202 can check for this condition. If the output exceeds 28V, the MP3202 will shut down. The part will not switch again until the power is recycled. Figure 9 shows the behavior of the MP3202 into an open load. Startup Waveforms into an Open Load FB VIN = 3.6V Figure 7—PWM Dimming Control Using a Logic Signal If the PWM signal is above 1KHz, dimming can be achieved using the circuit shown in Figure 8. LED1 MP3202 VOV 10V/div. VSW 10V/div. LED2 FB LED3 PWM Figure 8— Dimming Control Using a Filtered PWM Signal MP3202 Rev. 0.91 9/21/2007 VEN 5V/div. Figure 9—Startup Waveforms into an Open Load Layout Considerations Careful attention must be paid to the PCB board layout and component placement. Proper layout of the high frequency switching path is critical to prevent noise and electromagnetic interference problems. Due to high frequency switching, the length and area of all the traces connected to the switch node should be minimized. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 7 MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER PACKAGE INFORMATION TSOT23-6 6 See Note 7 EXAMPLE TOP MARK PIN 1 0.95 BSC 0.60 TYP 2.80 3.00 4 AAAA 1 1.20 TYP 1.50 1.70 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 MP3202 Rev. 0.91 9/21/2007 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 AB. 6) DRAWING IS NOT TO SCALE. 7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM LEFT TO RIGHT, (SEE EXAMPLE TOP MARK) www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 8 MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER QFN8 (2mm x 2mm) PIN 1 ID MARKING 1.90 2.10 0.25 0.45 0.18 0.30 1.90 2.10 PIN 1 ID INDEX AREA PIN 1 ID SEE DETAIL A 0.45 0.65 8 1 1.05 1.25 0.50 BSC 5 TOP VIEW 4 BOTTOM VIEW 0.80 1.00 PIN 1 ID OPTION A R0.20 TYP. PIN 1 ID OPTION B R0.20 TYP. 0.20 REF 0.00 0.05 SIDE VIEW DETAIL A NOTE: 1.90 0.70 0.60 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 VCCD-3. 5) DRAWING IS NOT TO SCALE. 0.25 1.20 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. MP3202 Rev. 0.91 9/21/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 9