MP3205DJ-LF-Z

TM MP3205 1.3MHz Fixed Frequency 5 White LED Driver The Future of Analog IC Technology TM DESCRIPTION FEATURES The MP3205 is a step-up converter designed for driving up to 5 series white LEDs from a single cell Lithium Ion battery. The MP3205 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 MP3205 includes under-voltage lockout, current limiting and thermal overload protection preventing damage in the event of an output overload. The MP3205 is available in a small 5-pin TSOT23 package. EVALUATION BOARD REFERENCE Board Number Dimensions EV3205DJ-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 Available in a TSOT23-5 Package APPLICATIONS • • • • Cell Phones Handheld Computers and PDAs Digital Still Cameras Small LCD Displays Application “MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION Efficiency vs LED Current CMDSH-3 VIN 5V LED1 EFFICIENCY (%) LED2 LED3 5 EN 4 2 1 IN EN LED4 SW LED5 MP3205 GND FB 3 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) MP3205-TAC-S01 MP3205 Rev. 1.3 10/8/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 20 MP3205-EC01 1 TM MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER PACKAGE REFERENCE ABSOLUTE MAXIMUM RATINGS (1) SW ............................................... –0.5V to +28V All Other Pins.............................. –0.3V to +6.5V Storage Temperature ..............–55°C to +150°C TOP VIEW SW 1 5 IN Recommended Operating Conditions GND 2 FB 3 4 IN Supply Voltage.............................. 2.5V to 6V Output Voltage....................................VIN to 21V Operating Temperature .............–40°C to +85°C EN Thermal Resistance MP3205-PD01_TSOT23 (3) θJA θJC TSOT23-5.............................. 220 .... 110.. °C/W Part Number* Package Temperature MP3205DJ TSOT23-5 –40°C to +85°C * (2) For Tape & Reel, add suffix –Z (eg. MP3205DJ–Z) For Lead Free, add suffix –LF (eg. MP3205DJ –LF–Z) 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. Parameter Symbol Using Parameter Set Heading Operating Input Voltage VIN Supply Current (Shutdown) Supply Current (Quiescent) Switching Frequency fSW Maximum Duty Cycle Undervoltage Lockout IN Under Voltage Lockout UVLO Under Voltage Lockout Hysteresis Enable EN Threshold EN Threshold EN Hysteresis EN Input Bias Current Feedback FB Voltage FB Input Bias Current Output Switch SW On-Resistance (4) RON SW Current Limit Thermal Shutdown (4) Condition Min Typ 2.5 VEN = 0V VFB = 0.15V VFB = 0V 1.0 85 VIN Rising 0.1 690 1.3 92 2.25 Max Units 6 1 750 1.5 V μA μA MHz % 2.45 V 92 VEN Rising VEN Rising, VIN = 2.5V 1.0 0.8 1.35 mV 1.6 90 VEN = 0V, 5V VFB = 0.1V Duty Cycle = 60% 1 94 –600 104 –300 0.5 350 160 114 V V mV μA mV nA Ω mA °C Note: 4) Guaranteed by design. MP3205 Rev. 1.3 10/8/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 2 TM MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER PIN FUNCTIONS Pin # Name Description 1 SW 2 GND 3 FB 4 EN 5 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 MP3205 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. Input Supply Pin. Must be locally bypassed. OPERATION The MP3205 uses a constant frequency, peak current mode boost regulator architecture to regulate the series string of white LEDs. The operation of the MP3205 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 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. FB When this voltage equals the 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. 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 to flow 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 MP3205-F03-BD01 Figure 1—Functional Block Diagram MP3205 Rev. 1.3 10/8/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 3 TM MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER APPLICATION INFORMATION VIN 2.5V to 6V CMDSH-3 5 1 IN OFF ON 4 2 EN LED1 SW LED2 MP3205 GND LED3 FB 3 MP3205_F02_AP_S01 Figure 2—Driving 3 White LEDs COMPONENT SELECTION 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 up to 1µF may be used. A 22μH inductor with low DCR (Inductor resistance) is recommended to improve efficiency. A 1μF 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 100mA to 200mA are sufficient for the MP3205. The switching characteristics during normal operation can be seen in Figure 3. The MP3205 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. Figure 4 shows the startup behavior of the MP3205. 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. MP3205_F04_WF02 Figure 4—Startup Waveforms VIN=3.6V, 3 LEDs, 20mA Figure 5 shows the dependence on current limit versus duty cycle. 500 CURRENT LIMIT (mA) VSW 5V/div. VOUT RIPPLE (AC COUPLED) 50mV/div. IL 100mA/div. 400 300 200 100 0 MP3205_F03_WF01 Figure 3—Steady-State Operation VIN=3.6V, 3 LEDs, 20mA MP3205 Rev. 1.3 10/8/2007 0 20 40 60 80 DUTY CYCLE (%) 100 MP3205_F05 Figure 5—Current Limit vs. Duty Cycle www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 4 TM MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER Setting the LED Current The LED current is controlled by the feedback resistor, R1, in Figure 2. The current through the LEDs is given by the equation 104mV/R1. Table 1 shows the selection of resistors for a given LED current. signal used in Figure 7 should be 1KHz or below due to the soft start function. LED1 LED2 Table 1—ILED vs. R1 ILED (mA) R1 (Ω) 1 5 10 15 20 104 20.8 10.4 6.93 5.2 Analog and Digital Dimming There are three different ways to control dimming for the MP3205 during normal operation. The first way uses a DC voltage to control the feedback voltage. This 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 LED3 PWM 4 MP3205 EN FB 3 MP3205_F07_S01 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 MP3205 LED2 FB 3 LED3 PWM LED1 MP3205_F08_S01 MP3205 FB LED2 Figure 8—Dimming Control Using a Filtered PWM Signal LED3 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 EV3205DJ-00A for a sample layout of theBMP3205. 3 MP3205_F06_S01 Figure 6—Dimming Control Using a DC Voltage Other applications need to use a logic signal to do the dimming. This can be seen in Figure 7. The PWM signal is applied to the EN pin of the MP3205. 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 MP3205 Rev. 1.3 10/8/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 5 TM MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER VIN 2.5V to 6V CMDSH-3 5 IN 4 OFF ON 2 LED1 1 EN LED2 SW LED3 MP3205 GND FB 3 MP3205_F09 Figure 9—LED Driver with Overload Protection PACKAGE INFORMATION TSOT23-5 2 .9 0 B S C 3 0 .9 5 0 TYP. 0 .9 5 0 TYP. CL 2.80BSC 1.60BSC 3 10癟 YP. (2 p l cs) 0 0.25 ? .10 Ga u g e P l a n e CL 0.87? .03 1.00Max. 0 .3 0 0 (M i n ) 0 .5 0 0 (M a x) (5 P L C S ) BSC . 0 .4 0 0 + 4 - 0 S E A T IN G P L A N E 0.00- 0.10 0 .1 2 7 T Y P . 1 0 ?T Y P . (2 p l c s ) D ime n sio n s a re in millime te rs Note: 1.Dimens ions and toleranc es are as per A NSI Y 14.5M, 1994. 2. Die is f ac ing up f or mold. Die is f ac ing dow n f or trim/f orm, ie. Rev ers e trim/f orm 3 3. Dimens ions are ex c lus iv e of mold f las h and gate burr. 4.The f ootlength meas uring is bas ed on the gauge plane method. 5. A ll s pec if ic ation c omply to Jedec Spec MO193 Is s ue C. NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications. 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. MP3205 Rev. 1.3 10/8/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 6