ACT6311UC-T

ACT6311 Rev 3, 22-Feb-11 White LED/OLED Step-Up Converter FEATURES • • • • • • Adjustable Output Voltage Drives OLEDs or White LEDs 30V High Voltage Switch 1MHz Switching Frequency Tiny Inductors and Capacitors Tiny SOT23-5 Package GENERAL DESCRIPTION The ACT6311 step-up DC/DC converter is optimized for driving OLEDs or white LEDs. It can provide an output voltage up to 24V. The device is capable of driving up to seven LEDs in series from a Lithium-Ion battery, with inherent current matching and uniform brightness. The ACT6311 incorporates a 30V high voltage switch. The device operates at 1MHz and allows the use of few external components. The ACT6311 is available in the tiny SOT23-5 package. APPLICATIONS • • • • • • OLED Applications Cell Phones Digital Cameras PDAs, Laptops MP3 Players GPS Efficiency vs. Output Current 100 ACT6311-0001 80 Efficiency (%) 60 VIN = 3.6V VIN = 3.6V VIN = 3V VIN = 3V 40 20 0 0 5 10 15 20 25 30 35 Output Current (mA) Figure 1. Typical Application Circuit Innovative PowerTM -1- www.active-semi.com Copyright © 2011 Active-Semi, Inc. ACT6311 Rev 3, 22-Feb-11 G Figure 2: Application as White LED Drive ORDERING INFORMATION PART NUMBER ACT6311UC-T TEMPERATURE RANGE -40°C to 85°C PACKAGE SOT23-5 PINS 5 TOP MARK YCXB PACKING TAPE & REEL PIN CONFIGURATION SW G FB 1 2 3 5 IN ACT6311 UC 4 SHDN SOT23-5 PIN DESCRIPTION PIN NUMBER 1 2 3 4 5 PIN NAME SW G FB SHDN IN PIN DESCRIPTION Switch Output. Connect this pin to the inductor and the Schottky diode. To reduce EMI, minimize the PCB trace path between this pin and the input bypass capacitor. Ground. Feedback Input. This pin is referenced to 1.24V Shutdown Control. Connect to a logic high to enable the device. Connect to a logic low to disable the device. Never leave the pin unconnected. Supply Input. Bypass to G with a capacitor 1µF capacitor or higher. Innovative PowerTM -2- www.active-semi.com Copyright © 2011 Active-Semi, Inc. ACT6311 ABSOLUTE MAXIMUM RATINGS Rev 3, 22-Feb-11 (Note: Exceeding these limits may damage the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability.) PARAMETER IN, SHDN Voltage SW Voltage FB Voltage Maximum Power Dissipation (derate 5mW/°C above TA = 50°C) Junction to Ambient Thermal Resistance (θJA) Operating Junction Temperature Lead Temperature (Soldering, 10 sec) VALUE -0.3 to 6 -0.3 to 30 -0.3 to VIN + 0.3 0.4 190 -40 to 150 300 UNIT V V V W °C/W °C °C ELECTRICAL CHARACTERISTICS (VIN = VSHDN = 3V, TA = 25°C, unless otherwise specified.) PARAMETER Input Voltage Range Feedback Voltage FB Input Current Supply Current Supply Current in Shutdown Switching Frequency Maximum Duty Cycle Switch Current Limit Switch On Voltage Switch Leakage Current SHDN Logic High Threshold SHDN Logic Low Threshold SHDN Input Current SYMBOL VFB TEST CONDITIONS VIN = 3V MIN 2.5 1.18 TYP 1.24 50 MAX UNIT 5.5 1.30 V V nA 1.5 1 1.2 mA µA MHz % mA mV 10 µA V 0.4 V µA SHDN = IN SHDN = G fSW DMAX ILIM 75% Duty Cycle ISW = 200mA VSW = 20V, SHDN = G 1.6 0.8 80 0.7 0 1 85 320 350 0 1 Innovative PowerTM -3- www.active-semi.com Copyright © 2011 Active-Semi, Inc. ACT6311 Rev 3, 22-Feb-11 ERROR AMPLIFIER Figure 3. Functional Block Diagram FUNCTIONAL DESCRIPTION The ACT6311 is a high efficiency step-up DC/DC converter that employs a current-mode, fixed frequency pulse-width modulation (PWM) architecture with excellent line and load regulation. Figure 3 shows the functional block diagram of the IC. The flip-flop is set at the start of each oscillator cycle, and turns on the power switch. During this on time, the switch current level is sensed and added to a ramp signal, and the resulting sum is compared with the output of the error amplifier. If the error comparator output is high, the flip-flop is reset and the power switch turns off. Thus, the peak inductor current level is controlled by the error amplifier output, which is integrated from the difference between FB input and the 1.24V reference point. The ACT6311 operates at a constant switching frequency for output current higher than 4mA. If the output current decreases further, the IC will enter frequency modulation mode, resulting in some low frequency ripple. Innovative PowerTM -4- www.active-semi.com Copyright © 2011 Active-Semi, Inc. ACT6311 APPLICATION INFORMATION Inductor Selection Table 1: Recommended Inductors PART NUMBER CDRH3D16-220 ELJPC220KF LQH3C220 LEM2520-220 Rev 3, 22-Feb-11 and determine R2 from the output voltage: ⎛V ⎞ R 2 = R 1 ⎜ OUT − 1 ⎟ ⎝ 1 . 24 V ⎠ (1) White LED Application SUPPLIER Sumida Panasonic Murata Taiyo Yuden CURRENT DCR RATING (Ω) (MA) 350 160 250 125 0.5 4.0 0.7 5.5 The LED current is determined by the value of the feedback resistor R1. Because the FB input of the IC is regulated to 1.24V, the LED current is determined by ILED = 1.24V/R1. The value of R1 for different LED currents is shown in Table 3. Table 3: R1 Resistor Value Selection ILED (MA) 5 10 12 15 20 A 22µH inductor is typically used for the ACT6311. The inductor should have low DC resistance (DCR) and losses at 1MHz. See Table 1 for examples of small size inductors. R1 (Ω) 246 124 103.3 82.7 62 Capacitor Selection The ACT6311 only requires a 1µF input capcitor and a 1µF output capacitor for most applications. Ceramic capacitors are ideal for these applications. For best performance, use X5R and X7R type ceramic capacitors, which possess less degradation in capacitance over voltage and temperature ranges. To improve efficiency, resistors R2 and R3 can be connected as shown in Figure 4 to lower the effective feedback voltage. The following are dimming control methods for the ACT6311 series white LED application. 1) PWM Signal Driving SHDN When a PWM signal is connected to the SHDN pin, the ACT6311 is turned on and off alternately under the control of the PWM signal. The current through the LEDs is either zero or full scale. By changing the duty cycle of the PWM signal (typically 1kHz to 10kHz), a controlled average current is obtained. 2) DC Voltage Control Figure 5 shows an application in which a DC voltage is used to adjust the LED current. The LED current increases when VDC is lower than VFB and decreases when VDC is higher than VFB. In Figure 5, the LED current range of 15mA to 0mA is controlled by VDC = 0V to 2V. 3) Filtered PWM Control Figure 6 shows an application using a filtered PWM signal to control dimming. 4) Logic Control A logic signal can be used to adjust the LED current in a discrete step, as shown in Figure 7. -5www.active-semi.com Copyright © 2011 Active-Semi, Inc. Diode Selection The ACT6311 requires a fast recovery Schottky diode as the rectifier. Select a low forward voltage drop Schottky diode with a forward current (IF) rating of 100mA to 200mA and a sufficient peak repetitive reverse voltage (VRRM). Some suitable Schottkky diodes are listed in Table 2. Table 2: Recommended Schottky Diodes PART NUMBER CMDSH-3 CMDSH2-3 BAT54 IF(MA) 100 200 200 VRRM (V) 30 30 30 SUPPLIER Central Central Zetex OLED Application Figure 1 shows the feedback network necessary to set the output voltage. Select the proper ratio of the two feedback resistors R1 and R2 based on the desired output voltage. Typically choose R1 = 20kΩ Innovative PowerTM ACT6311 LED1 LED2 LED3 Rev 3, 22-Feb-11 ACT6311 FB R2 R1 LOGIC Figure 4. Current Setting for White LED Application Figure 7. Logic Controlled Dimming Start-up and Inrush Current LED1 LED2 LED3 R2 56k ACT6311 FB R3 VDC 33.4k In order to facilitate quick startup, a soft-start circuit is not incorporated into the ACT6311. When the IC is first turned on with no external soft-start circuit, the peak inrush current is about 400mA. Figure 8 shows an implementation for soft-start. When soft-start and dimming controls are used simultaneously, a low frequency PWM signal (less than 10kHz) or the methods in Figures 5, 6 and 7 should be used. R1 62Ω Open-Circuit Protection (White LEDs) If one of the LEDs is disconnected, the FB voltage drops to zero and the IC switches at maximum duty cycle. This results in a high voltage that may exceed the SW voltage rating. To limit this voltage, use a Zener diode as shown in Figure 9. The Zener voltage must be large than the total forward voltage of the LEDs and the current rating should be higher than 0.1mA. Figure 5. DC Voltage Controlled Dimming LED1 Board Layout ACT6311 FB R4 PWM 10k 33.4k C1 0.1µF 56k R1 62Ω R3 R2 LED2 LED3 To reduce EMI, minimize the area and path length of all traces connected to SW. Use a ground plane under the switching regulator and connect R1 directly to the G pin of the IC. Figure 6. Filtered PWM Controlled Dimming Innovative PowerTM -6- www.active-semi.com Copyright © 2011 Active-Semi, Inc. ACT6311 D1 OUTPUT Rev 3, 22-Feb-11 C1 100nF ACT6311 FB D2 R2 200k R3 56k R1 20k Figure 8: Soft-Start Circuit Figure 9: Open-Circuit Protection Innovative PowerTM -7- www.active-semi.com Copyright © 2011 Active-Semi, Inc. ACT6311 TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 1, unless otherwise specified.) Rev 3, 22-Feb-11 Efficiency vs. Output Voltage 100 90 80 1.10 Switching Frequency vs. Temperature Switching Frequency (MHz) ACT6311-0001 ACT6311-0002 1.05 Efficiency (%) 70 60 50 40 30 20 10 0 0 5 10 15 20 25 30 VIN = 3.6V VIN = 3V 1.00 0.95 0.90 35 -40 -15 10 35 60 85 Output Current (mA) Temperature (°C) Current Limit vs. Duty Cycle 450 1.30 ACT6311-0003 FB Voltage vs. Temperature ACT6311-0004 Current Limit (mA) FB Voltage (V) 400 1.25 250 1.20 300 VIN = 3V 20 30 40 50 60 70 80 1.15 250 1.10 -40 -15 10 35 60 85 Duty Cycle (%) Temperature (°C) Load Regulation 14.0 14.0 ACT6311-0005 Line Regulation ACT6311-0006 Output Voltage (V) Output Voltage (V) 13.5 13.5 13.0 13.0 12.5 VIN = 3.6V 0 5 10 15 20 25 30 35 12.5 12.0 12.0 3.0 IOUT = 20mA 3.5 4.0 4.5 5.0 5.5 Load (mA) Input Voltage (V) Innovative PowerTM -8- www.active-semi.com Copyright © 2011 Active-Semi, Inc. ACT6311 TYPICAL PERFORMANCE CHARACTERISTICS CONT’D (Circuit of Figure 1, unless otherwise specified.) Rev 3, 22-Feb-11 Switching Waveform in Discontinuous Mode ACT6311-0007 Startup without Soft Start Circuit ACT6311-0008 SW 5V/DIV Inductor Current 100mA/DIV VOUT 200mV/DIV Inductor Current 200mA/DIV VOUT 5V/DIV VIN = 3V No load 1µs/DIV VIN = 3.6V ILOAD = 20MA 20µs/DIV SHDN Startup with Soft Start Circuit ACT6311-0009 Load Step Response ACT6311-0010 VIN = 3.6V VOUT = 13.6V VOUT 1V/DIV Inductor Current 50mA/DIV VOUT 5V/DIV VIN = 3.6V ILOAD = 20mA Test Circuit Figure 8 4ms/DIV 20mA Load Step 2mA SHDN 100µs/DIV Line Step Response ACT6311-0011 VOUT = 13.6V IOUT = 10mA VOUT 500mV/DIV 5.5V VIN 3V 100µs/DIV Innovative PowerTM -9- www.active-semi.com Copyright © 2011 Active-Semi, Inc. ACT6311 PACKAGE OUTLINE SOT23-5 PACKAGE OUTLINE AND DIMENSIONS Rev 3, 22-Feb-11 SYMBOL A A1 A2 b c D E E1 e e1 L DIMENSION IN MILLIMETERS MIN 0.000 0.900 0.300 0.080 DIMENSION IN INCHES MIN 0.000 0.035 0.012 0.003 MAX 1.450 0.150 1.300 0.500 0.220 MAX 0.057 0.006 0.051 0.020 0.009 2.900 BSC 1.600 BSC 2.800 BSC 0.950 BSC 1.900 BSC 0.60REF 0.300 0° 0.600 8° 0.114 BSC 0.063 BSC 0.110 BSC 0.037 BSC 0.075 BSC 0.024REF 0.012 0° 0.024 8° L1 θ Active-Semi, Inc. reserves the right to modify the circuitry or specifications without notice. Users should evaluate each product to make sure that it is suitable for their applications. Active-Semi products are not intended or authorized for use as critical components in life-support devices or systems. Active-Semi, Inc. does not assume any liability arising out of the use of any product or circuit described in this datasheet, nor does it convey any patent license. Active-Semi and its logo are trademarks of Active-Semi, Inc. For more information on this and other products, contact sales@active-semi.com or visit http://www.active-semi.com. ® is a registered trademark of Active-Semi. - 10 www.active-semi.com Copyright © 2011 Active-Semi, Inc. Innovative PowerTM