MP3204DJ-LF-P

TM MP3204 1.3MHz Fixed Frequency 5 White LED Driver with Open LED Protection The Future of Analog IC Technology TM DESCRIPTION FEATURES The MP3204 is a step-up converter designed for driving up to 5 series white LEDs from a single cell Lithium Ion battery. The MP3204 uses 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 MP3204 includes under-voltage lockout, current limiting and thermal overload protection preventing damage in the event of an output overload. The MP3204 is available in a small 6-pin TSOT23 package. APPLICATIONS EVALUATION BOARD REFERENCE Board Number Dimensions EV3204DJ-00A 1.9”X x 1.8”Y x 0.4”Z • • • • On Board Power MOSFET Drives up to 5 Series White LEDs Up to 87% Efficiency Over 1MHz Fixed Switching Frequency Low 104mV Feedback Voltage Soft-Start/PWM Dimming UVLO, Thermal Shutdown Internal Current Limit Open Load Shutdown Available in a TSOT23-6 Package Cell Phones Handheld Computers and PDAs Digital Still Cameras Small LCD Displays “MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION Efficiency vs LED Current VIN 5V LED1 LED3 6 EN 4 2 MP3204 Rev. 1.4 10/8/2007 IN EN 1 SW 5 OV MP3204 GND FB 3 LED4 LED5 EFFICIENCY (%) LED2 88 87 86 85 84 83 82 81 80 79 78 77 4 LEDs 5 LEDs 3 LEDs VIN=3.6V 5 10 15 LED CURRENT (mA) www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 20 1 TM MP3204 – 6V, 1.3MHz WHITE LED DRIVER ABSOLUTE MAXIMUM RATINGS (1) PACKAGE REFERENCE SW, OV Pins ............................... –0.5V to +28V All Other Pins.............................. –0.3V to +6.5V Storage Temperature .............. –55°C to +150°C TOP VIEW SW 1 6 IN Recommended Operating Conditions GND 2 5 OV FB 3 4 EN IN Supply Voltage.............................. 2.5V to 6V Output Voltage....................................VIN to 21V Operating Temperature ............. –40°C to +85°C Thermal Resistance Part Number* Package Temperature MP3204DJ TSOT23-6 –40°C to +85°C * (2) For Tape & Reel, add suffix –Z (eg. MP3204DJ–Z) For RoHS Compliant Packaging, add suffix –LF (eg. MP3204DJ–LF–Z) (3) θJA θJC TSOT23-6.............................. 220 .... 110.. °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 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 Threshold EN Threshold EN Hysteresis Condition VIN Min Typ 2.5 VEN = 0V VFB = 0.15V fSW VFB = 0V UVLO VOV 0.1 690 1.3 92 1.0 85 VIN Rising 2.25 VOV Rising VEN Rising VEN Rising, VIN = 2.5V 1.0 0.8 Units 6 1 750 1.5 V µA µA MHz % 2.45 V 92 mV 28 V 1.35 1.6 V V mV 1 μA 114 mV nA 90 EN Input Bias Current VEN = 0V, 5V Feedback FB Voltage FB Input Bias Current Output Switch SW On-Resistance (4) SW Current Limit Max VFB = 0.1V 94 –600 104 –300 RON Duty Cycle = 60% Thermal Shutdown (4) 0.5 350 Ω mA 160 °C Note: 4) Guaranteed by design, not tested. MP3204 Rev. 1.4 10/8/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 2 TM MP3204 – 6V, 1.3MHz WHITE LED DRIVER PIN FUNCTIONS Pin # Name Description 1 SW 2 GND 3 FB 4 EN 5 OV 6 IN 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 MP3204 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. This pin must be locally bypassed. OPERATION The MP3204 uses constant frequency, peak current mode boost regulator architecture to regulate a series of white LEDs. The operation of the MP3204 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 subharmonic 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 FB 3 output voltage of the error amplifier, the power FET is turned off. 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. This is the manner in which the peak current level keeps the output in regulation. If the feedback voltage begins 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 1 SW PWM COMPARATOR 104mV + + 2 GND CURRENT SENSE AMPLIFIER 1.3MHz OSC Figure 1—Functional Block Diagram MP3204 Rev. 1.4 10/8/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 3 TM MP3204 – 6V, 1.3MHz WHITE LED DRIVER APPLICATION INFORMATION VIN 2.5V to 6V CMDSH-3 LED1 LED2 OFF ON 4 2 6 IN EN 1 SW MP3204 GND OV FB 5 LED3 3 Figure 2—Driving 3 White LEDs A typical application circuit can be seen in Figure 2. The 3 white LEDs can be driven from a voltage supply range of 2.5V to 6V at an output current of 20mA. A 0.22µF output capacitor is sufficient for most applications but an output capacitor of up to 1µF may be used. A 22µH inductor with low DCR (inductor resistance) is recommended for improved efficiency. A 1µF ceramic capacitor is recommended for the input capacitance in the real system. Schottky diodes have fast recovery times and a low forward voltage and are also recommended. Schottky diodes with ratings of 100mA to 200mA are sufficient for use with the MP3204. The switching characteristics during normal operation can be seen in Figure 3. The MP3204 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 current limit is increased by a fourth every 40µs, giving a total soft start time of 120µs. MP3204 Rev. 1.4 10/8/2007 VSW 5V/div. VOUT RIPPLE (AC COUPLED) 50mV/div. IL 100mA/div. Figure 3—Steady-State Operation (VIN=3.6V, 3 LEDs, 20mA) www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 4 TM MP3204 – 6V, 1.3MHz WHITE LED DRIVER Figure 4 shows the startup behavior of the MP3204. 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. VEN 5V/div. VOUT 5V/div. IIN 100mA/div. Figure 4—Startup Waveforms (VIN=3.6V, 3 LEDs, 20mA) Figure 5 shows the dependence on current limit versus duty cycle. Table 1—ILED vs. R1 ILED (mA) 1 5 10 15 20 R1 (Ω) 104 20.8 10.4 6.93 5.2 Analog and Digital Dimming There are three different ways to control dimming for the MP3204 during normal operation. The first way uses a DC voltage to control the feedback voltage, which can be seen 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 500 CURRENT LIMIT (mA) LED1 400 LED2 300 LED3 200 MP3204 FB 3 100 0 0 20 40 60 80 DUTY CYCLE (%) 100 Figure 5—Current Limit vs. Duty Cycle Figure 6—Dimming Control Using a DC Voltage Setting the LED Current The LED current is controlled by the feedback resistor, R1, as shown in Figure 2. The current through the LEDs is equal to 104mV/R1. Table 1 shows the selection of resistors for a given LED current. MP3204 Rev. 1.4 10/8/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 5 TM MP3204 – 6V, 1.3MHz WHITE LED DRIVER Other applications require the use of a logic signal to execute the dimming. This can be seen in Figure 7. The PWM signal is applied to the EN pin of the MP3204. The LEDs will switch between full load to complete shutoff. The average current through the LEDs will increase proportionally to the duty cycle of the PWM signal. The signal used in Figure 7 should be 1KHz or below due to the soft-start function. LED1 LED2 LED3 PWM 4 MP3204 EN FB 3 Figure 7—PWM Dimming Control Using a Logic Signal If the PWM signal is above 1KHz, dimming can be achieved by using the circuit shown in Figure 8. LED1 MP3204 LED2 FB 3 LED3 PWM Figure 8—Dimming Control Using a Filtered PWM Signal MP3204 Rev. 1.4 10/8/2007 Open Load Protection Open Load protection will shutoff the MP3204 if the output voltage goes too high when the OV pin is tied to the output. In some cases an LED may fail, which will result in the feedback voltage always being zero. The part will run at the maximum duty cycle, boosting the output voltage higher and higher. By tying the OV pin to the top of the LED string the MP3204 checks the said condition and if the output ever exceeds 28V the MP3204 will shutdown. The part will not switch on again until the power is recycled. Figure 9 shows the behavior of the MP3204 into an open load. VEN 5V/div. VOV 10V/div. VSW 10V/div. Figure 9—Startup Waveforms into an Open Load (VIN=3.6V) 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 the high frequency switching, the length and area of all the traces connected to the switch node should be minimized. Refer to the evaluation board EV3204DJ-00A for a sample layout of theBMP3204. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 6 TM MP3204 – 6V, 1.3MHz 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 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) 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. MP3204 Rev. 1.4 10/8/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 7