SP6682 High Efficiency Charge Pump Regulator for White LEDs FEATURES ■ Ideal For White LED Driver ■ Low Profile, Inductorless Regulator ■ Output Current up to 200mA ■ X1.5 and X2 Modes for Highest Efficiency ■ +2.7V to +5.5V Input Voltage Range ■ Fast Turn-On Time, 175µS ■ 1mA Quiescent Current ■ <1.5µA Shutdown Current ■ 600kHz Oscillator ■ Programmable Output Current or Voltage ■ PWM Dimming Control with Enable Pin ■ Shutdown to Disconnect Output from Input ■ Soft Start to Eliminate In-Rush Current ■ Industry Standard 10-pin MSOP Package and Small 10-pin DFN Package V OUT 1 C1P 2 V IN 3 V MODE 4 FB 5 SP6682 10 Pin DFN 10 C2P 9 C1N 8 GND 7 C2N 6 EN/PWM Now Available in Lead Free Packaging APPLICATIONS ■ Next Generation Mobile Phones ■ PDAs ■ 3.3V to 5.0V Conversion ■ Palmtop Computers ■ Color LCD Modules DESCRIPTION The SP6682 is a current regulated charge pump ideal for converting a Li-Ion battery input for driving white LEDs used in backlighting color displays or cell phone camera flash applications. The charge pump automatically switches between X1.5 and X2 modes based on the programmable VMODE voltage, providing improved efficiency over traditional methods using charge pump doubler followed by LDO. This input voltage threshold can be externally programmed by a resistor divider network for optimized efficiency at specific output voltages and currents. The SP6682 operates with an internal 600kHz clock, which reduces switching noise and improves VOUT ripple. Output current or voltage can be accurately regulated by modulating the switcher between the charge pump and output capacitor. In shutdown mode, the IC disconnects the output from the input and draws less than 1.5µA current. The SP6682 is offered in a 10-pin MSOP package, and a small 10-Pin DFN Package. TYPICAL APPLICATION SCHEMATIC LCD BACKLIGHT APPLICATION C2 2.2µF ® 1 V OUT 2 C1P C2P 10 SP6682 C1N 9 3 8 VIN GND 4 7 VMODE C2N 5 6 FB EN/PWM 2.7 - 4.2V Lithium-Ion C1 2.2µF C6 0.1µF C4 2.2µF C5 2.2µF White LED R6 20 ENABLE/PWM DIMMING Date: 7/19/06 Rev D 20 20 20 R3 1M SP6682 High Efficiency Charge Pump Regulator for White LEDs 1 © 2006 Sipex Corporation TYPICAL APPLICATION SCHEMATIC Iout=200mA for 1W LED CAMERA FLASH APPLICATION LEDA SP6682 1 Vin: 3.0-4.2V 10 Vout C2P C1P C1N 2 9 3 Vin GND Vmode C2N 1W LED 7 4 C5 2.2uF 6 5 EN/PWM FB C1 2.2uF C4 2.2uF 8 LEDK VFB=300mV R3 1.0M Rfb 1.5 Ohm ENABLE/PWM ABSOLUTE MAXIMUM RATINGS VIN, VMODE, VOUT and EN/PWM ................. -0.3V to 6V VIN - VOUT ........................................................... 0.7V Output Current (IOUT) ...................................... 300mA Power Dissipation per Package - 10-pin MSOP (derate 8.84mW/°C above +70°C) ................. 720mW Junction Temperature .................................... +125°C Storage Temperature ...................... -65°C to +150°C ESD Rating. ................................................ 2kV HBM These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. ELECTRICAL CHARACTERISTICS Unless otherwise specified: VIN =+2.7V to +5.0V, C1=C2=C4=C5=2.2µF (ceramic, ESR=0.03�), C3=0.1µF (ceramic) and TAMB =-40°C to +85°C unless otherwise noted. PARAMETER MIN Input Voltage 2.7 Quiescent Current TYP MAX UNITS 5.5 V 1.2 3 mA Shutdown Current CONDITIONS VIN = 4.2V, VOUT = 3.6V, IOUT = 100µA 1.5 µA Oscillator Frequency 0.42 0.60 0.78 MHz VFB Reference Voltage 0.275 0.306 0.337 V 11 18 �� FB = 0.0V, VIN = 3.6V, IOUT = 20mA, VMODE = High 1.25 1.35 V VIN Falling @ 25°C mVPP VIN = 3.6V @ 25°C Charge Pump Output Resistance VMODE Threshold Voltage 1.15 Hysteresis for Mode Transition Voltage 30 VMODE Pin Current 0.01 EN/PWM Logic Low EN/PWM Logic High EN/PWM Pin Current Date: 7/19/06 Rev D µA 0.4 V 1.6 VMODE = 1.25 V 0.01 FB Pin Current VOUT Turn-On Time 0.5 EN/PWM = 0.0V, VIN = 5.5V VIN = 3.6V 175 0.5 µA VEN/PWM = 4.2V 0.5 µA VFB = 1V 500 µs VIN = 3.6V, FB within 90% regulation SP6682 High Efficiency Charge Pump Regulator for White LEDs 2 © 2006 Sipex Corporation PERFORMANCE CHARACTERISTICS Refer to the typical application circuit, TAMB = 25 C, IO = 60mA unless otherwise specified. O EN/PWM 90 5V/DIV 80 70 VOUT Efficiency (%) 1V/DIV 60 50 40 30 20 10 0 2.7 3 3.3 3.6 3.9 4.2 3.9 4.2 Input Voltage(V) Figure 1. Output voltage turn-on time Figure 2. Power efficiency vs. input voltage 0.34 50mV/DIV VIN 0.33 VOUT VFB (V) 0.32 50mV/DIV 0.31 0.3 0.29 0.28 0.27 0.26 2.7 3 3.3 3.6 VIN (V) Figure 4. Feedback pin voltage vs. input voltage Figure 3. X2 mode voltage ripple when VIN = 2.7V VIN 1 50mV/DIV 0.9 VOUT ISUPPLY (mA) 0.8 50mV/DIV 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 2.7 3 3.3 3.6 3.9 4.2 VIN (V) Figure 5. X1.5 mode voltage ripple when VIN = 3.3V Date: 7/19/06 Rev D Figure 6. Quiescent current vs. input voltage SP6682 High Efficiency Charge Pump Regulator for White LEDs 3 © 2006 Sipex Corporation PERFORMANCE CHARACTERISTICS: Continued Refer to the typical application circuit, TAMB = 25°C, IO = 60mA unless otherwise specified. 6 3 Brigtness, kCd/m2 Brightness (kcd/m2) 5 4 3 2 1 0 2.7 3 3.3 3.6 3.9 Input Voltage (V) 4 LED's @ 30mA 2 1 0 4.2 100 Hz 500 Hz 0 20 40 60 80 100 Duty Cycle,% 4 LED's @ 15mA Figure 7. Brightness vs. input voltage Figure 8. Brightness vs. duty cycle SP6682 IOUT vs VIN 250 IOUT (mA) 200 150 SP6682 Luxeon I, VF = 3.2V 100 50 0 3.0 3.2 3.4 3.6 VIN (V) 3.8 4.0 4.2 Figure 9. IOUT vs. VIN Date: 7/19/06 Rev D SP6682 High Efficiency Charge Pump Regulator for White LEDs 4 © 2006 Sipex Corporation OPERATION GENERAL OVERVIEW The SP6682 is a current regulated charge pump ideal for converting a Li-Ion battery input for driving white LEDs used in backlighting color displays, Cell Phone Camera Flash, PDAs, digital cameras and MP3 players. The SP6682ʼs proprietary AutoBoost feature enables the IC to automatically transition from X1.5 boost mode to X2 boost mode based on battery input voltage for optimal efficiency and performance. The SP6682 is able to efficiently drive up to six 20mA white LEDs in parallel and maintain a constant brightness over a very wide operating voltage range (2.7V to 5.5V). The SP6682 operates with an internal 600kHz clock, enabling the use of small external components. Other features of SP6682 include PWM dimming control as well as complete input/out disconnect in shutdown. In shutdown mode the IC draws less than 1.5µA current. The output regulation is achieved by sensing the voltage at the feedback pin and modulating the switcher between the charge pump and output capacitor. an input voltage to the mode comparator which sets the logic state of the mode selection outputs to the X2 or X1.5 modes. VMODE is compared to a 1.25V bandgap voltage. For example, if one makes a 158K�/100K�� divider, the mode will change at 2.58 x 1.25 V = 3.23V. A comparator-based cycle-bycycle regulation ensures that no mode change occurs during cycles. 3) Clock Manager. An internal 600 kHz clock is generated in this block. Depending on the mode control, the appropriate clock phasing is generated here and sent to the start-up and charge-pump switches block. 4) Start-up and Charge Pump Switches. During start-up, until the reference is established, this block keeps the charge pump inactive. During this period the output stays floating, and by consequence the charge pump drivers are now referenced to VOUT. Charging of the output will occur (e.g. when VIN is ramped up to 4.2V, VOUT ramps only up to about 3V), but not to the value of VIN, protecting the White LEDs from experiencing high input voltages. Another important operation of this block is the PWM/EN dimming control, which is implemented in the delay of each pump driver, so that the enable high pulse width is proportional to the delay of the individual pump switches. THEORY OF OPERATION The SP6682 regulated charge pump block diagram consists of four main blocks (Voltage Reference, Mode Control, Clock Manager, Start-up and Charge-Pump Switches) and two comparators (VMODE Comparator and VOUT Comparator). 5) VOUT Comparator and Output Control. A 306mV reference voltage is compared to feedback output voltage to control the VOUT needed for the application. Output current is set by a bias resistor from FB pin to GND pin chosen by the relationship: I = VFB 1) Voltage Reference. This block provides the 306mV and 1.25V reference voltages needed for the two comparators. OUT 2) Mode Control. An external voltage divider connected to the VMODE pin will define Date: 7/19/06 Rev D RFB where VFB = 306mV. SP6682 High Efficiency Charge Pump Regulator for White LEDs 5 © 2006 Sipex Corporation APPLICATION INFORMATION CONFIGURING THE SP6682 AS VOLTAGE OR CURRENT SOURCE A 3-wire white LED module with internal series resistors as shown in figure 11 can also be driven in this way. The white LED load configuration used by customers can be discrete white LEDs or a white LED module. Inside the white LED module, there may or may not be resistors in series with the white LEDs. According to the different application requirements, the SP6682 can be configured as either a voltage source or a current source to provide solutions for these different applications, as shown in figures 10-13. Anode FB 3-wire W-LED module Figure 10 shows a circuit using the SP6682 to drive discrete white LEDs as a current source. VOUT GND Fig 11. 3-wire white LED module In Figure 12, the SP6682 was used to drive a 2-wire white LED module without internal series resistors as a current source. The bias resistor RB is selected to regulate the total current of the white LED module instead of the current of single LED as in Figure 10. 1 SP6682 FB 5 Rb GND Rb VOUT 2.2uF Anode 1 8 SP6682 2-wire W-LED module Figure 10. Driving discrete white LEDs as current source VFB 5 GND Rb 8 The current in one white LED current is set by the ratio of the feedback pin voltage (306mV) and the bias resistor RB. To set the operating current, RB can be selected by: Figure 12. Driving 2-wire white LED module as current source In this application, the bias resistor can be selected by: R = VFB RB = VFB ILED B The current of the remaining white LEDs is set according to the similarity of the white LEDs. Date: 7/19/06 Rev D Cathode ILED (TOTAL) where ILED(TOTAL) is the total operating current of all the white LEDs. SP6682 High Efficiency Charge Pump Regulator for White LEDs 6 © 2006 Sipex Corporation APPLICATION INFORMATION: Continued The guideline for divider resistor selections is as follows: For high input voltage, the SP6682 will work in X1.5 mode. When the input voltage drops to the VTH threshold voltage, it will switch to X2 mode automatically. The VTH threshold voltage for mode change can be calculated by: To use the SP6682 as a voltage source for fixed voltage applications, a voltage divider is needed to program the ouput voltage, as shown in Figure 13. VOUT Anode 1 R5 SP6682 VTH = (VF + 0.306 + M • ILED • ROUT)/1.5 2.2uF VFB 5 Where VF and M are the forward voltage and number of the white LEDs, ROUT is the output resistance of the SP6682. R6 GND 2-wire W-LED module 8 Cathode The equation for the voltage divider R1 and R2 with VMODE = 1.25V is: Figure 13. Driving 2-wire white LED module as voltage source VTH = 1.25V • (1+R1/R2) The output voltage is set by the ratio of the two resistors and the feedback control voltage as shown by: VOUT = ( 1 + which can be expressed as R1: R1 = (VTH / 1.25 -1) • R2 R5 ) • VFB R6 For the typical SP6682 application, Using VF=3.6V, M=4, ILED=15mA, ROUT=16�, the VTH will be 3.24V. Select R2=100k�, then R1=158k�. PROGRAMMING THE OPERATING MODE SP6682 can automatically change from X1.5 mode to X2 mode for highest efficiency. To use this feature, divider resistors should be chosen according to the specific application, as shown in Figure 14. 3 VIN R1 4 CAPACITOR SELECTION Ceramic capacitors are recommended for their inherently low ESR, which will help produce low peak to peak output ripple, and reduce high frequency spikes. The fly capacitor controls the strength of the charge pump. Selection of the fly capacitor is a trade-off between the output voltage ripple and the output current capability. Decreasing the fly capacitor will reduce the output voltage ripple because less charge will be delivered to the output capacitor. However, smaller fly capacitors lead to larger output resistance, thus decreasing the out- VIN SP6682 VMODE R2 C2 GND 8 Figure 14. Programming the Vmode Resistors Date: 7/19/06 Rev D SP6682 High Efficiency Charge Pump Regulator for White LEDs 7 © 2006 Sipex Corporation APPLICATION INFORMATION: Continued I1 put current capability and the circuit efficiency. Place all the capacitors as close to the SP6682 as possible for layout. Increasing the value of the input and output capacitors could further reduce the input and output ripple. I2 = VOUT - VF1 VOUT - VF2 where I1, I2 are the operating current of the white LEDs andVF1,VF2 are the forward voltage of the white LEDs. Refer to Table 1 for some suggested low ESR capacitors. MANUFACTURER PART NUMBER CAPACITANCE/ VOLTAGE CAPACITOR/ SIZE/TYPE ESR AT 100kHz TDK C2012X5R1A225K 2.2µF/10V 0805/X5R 0.030� TDK C2012X5R0J475K 4.7µF/6.3V 0805/X5R 0.020� MURATA GRM188R60J225KE01D 2.2µF/6.3V 0603/X5R 0.030� MURATA GRM219R60J475KE01D 4.7µF/6.3V 0805/X5R 0.020� Table 1: Suggested Low ESR Capacitors BRIGHTNESS CONTROL USING PWM Since the brightness of the white LED is proportional to the operating current, for better brightness matching, a higher output voltage could be used. This could be done by using a larger resistor, as shown in Figure 15. RB2 is used to bias the operating current of the white LED, RB1 is used to increase the output voltage. Better brightness matching was achieved at the cost of the power wasted on the bias resistor. Dimming control can be achieved by applying a PWM control signal to the EN/PWM pin. The brightness of the white LEDs is controlled by increasing and decreasing the duty cycle of the PWM signal. While the operating frequency range of the PWM control is from 60Hz to 700Hz, the recommended maximum brightness frequency range of the PWM signal is from 60Hz to 200Hz. A repetition rate of at least 60Hz is required to prevent flicker. BRIGHTNESS MATCHING For white LEDs, the forward voltage drop is a function of the operating current. However, for a given current, the forward voltage drops do not always match due to normal manufacturing tolerances, thus causing uneven brightness of the white LEDs. VOUT 1 I2 I1 In D1 D2 Dn VF1 VF2 VFn SP6682 5 VFB In Figure 15, assume high-precision bias resistors were used, the operating current ratio of two different branches can be easily derived as shown by: Rb1 Rb Rb Rb2 GND 8 Rb Figure 15. Increasing brightness matching Date: 7/19/06 Rev D SP6682 High Efficiency Charge Pump Regulator for White LEDs 8 © 2006 Sipex Corporation APPLICATION INFORMATION: Continued POWER EFFICIENCY The efficiency of driving the white LEDs can be calculated by: � = VF • I F = SP6682 HIGH VOLTAGE WHITE LED DRIVER The SP6682 can also be configured as a high voltage boost converter to drive more than 10 white LEDs. Figure 16 shows the schematic of this application as well as actual data showing efficiency of > 85%. By using an external inductor, MOSFET and diode, high output voltages can be generated to drive 12 white LEDs (2 branches -- each branch has 6 white LEDs in series). The current through the white LEDs is determined by: VF • IF � VF Vi • n Vi • (n • IF + I Q) Vi •Ii Where Vi, Ii are input voltage and current VF, IF are the forward voltage and operating current of White LEDs; IQ is quiescent current, which is considered small compared with IF; n is the boost ratio (X1.5 or X2). ILED = 4.7uH SP6682 2 Vin: 2.7-4.2V 3 4 5 C1 10uF X5R Ceramic VOUT C2P C1P C1N VIN GND VMODE FB R3 1M C2N EN/PWM D1 D7 D2 D8 D3 D9 D4 D10 D5 D11 D6 D12 95 10 9 8 7 6 Q1 SI1304 2.2uF 25V C3 X5R Ceramic SOT23 25V EN/PWM Efficiency (%) 1 100 ILED = VFB/R1 = 20mA DS SCHOTTKY MBR0530 L1 LQH32CN4R7M11 VFB R1 90 85 80 75 R1 15 70 R2 15 2.7 3.0 3.3 3.6 3.9 4.2 VIN (V) Figure 16. Using SP6682 as a High Voltage White LED Driver PINOUTS V OUT 1 C1P 2 V IN 3 MODE 4 FB 5 V Date: 7/19/06 Rev D SP6682 10 Pin DFN 10 C2P VOUT 1 9 C1N C1P 2 8 GND VIN 3 7 C2N VMODE 4 6 EN/PWM 10 C2P SP6682 10 Pin MSOP FB 5 SP6682 High Efficiency Charge Pump Regulator for White LEDs 9 9 C1N 8 GND 7 C2N 6 EN © 2006 Sipex Corporation PACKAGE: 10 PIN MSOP FRONT VIEW TOP VIEW D D/2 ø1 R1 Gauge Plane e1 R L2 10 8 9 7 6 ø E/2 E L Seating Plane c ø1 E1 2 1 (L1) 1 3 2 e 4 Seating Plane 5 Pin #1 designator to be within this INDEX AREA (D/2 * E1/2) A1 10 Pin MSOP SYMBOL A1 c R R1 ø ø1 A A2 b D E E1 e e1 L L1 L2 JEDEC MO-187 Dimensions in Millimeters: Controlling Dimension MIN 0.00 0.08 0.07 0.07 0º 5º 0.75 0.17 NOM 0.85 3.00 BSC 4.90 BSC 3.00 BSC 0.50 BSC 2.00 BSC 0.40 0.60 0.95 REF 0.25 BSC SIDE VIEW b Variation BA Dimensions in Inches Conversion Factor: 1 Inch = 25.40 mm MAX 0.15 0.23 8º 15º 1.10 0.95 0.33 MIN 0.000 0.004 0.003 0.003 0º 5º 0.030 0.007 0.80 0.016 SIPEX Pkg Signoff Date/Rev: Date: 7/19/06 Rev D A2 A NOM 0.034 0.118 BSC 0.193 BSC 0.118 BSC 0.020 BSC 0.079 BSC 0.024 0.037 REF 0.010 BSC MAX 0.006 0.009 8º 15º 0.043 0.038 0.013 0.032 JL Aug09-05 RevA SP6682 High Efficiency Charge Pump Regulator for White LEDs 10 © 2006 Sipex Corporation PACKAGE: 10 PIN DFN D D/2 ø E/2 A E (A3) A1 Seating Plane SIDE VIEW Pin1 Designator to be within this INDEX AREA (D/2 x E/2) TOP VIEW D2 D2/2 1 2 3 4 5 INDEX AREA (D/2 x E/2) E2/2 E2 K L 10 9 8 7 e 6 b BOTTOM VIEW 3x3 10 Pin DFN SYMBOL JEDEC MO-229 Dimensions in Millimeters: Controlling Dimension NOM 0.90 0.02 0.20 REF 0.20 0º b 0.18 0.25 D 3.00 BSC D2 2.20 E 3.00 BSC E2 1.40 e 0.50 BSC L 0.30 0.40 SIPEX Pkg Signoff Date/Rev: A A1 A3 K ø Date: 7/19/06 Rev D MIN 0.80 0.00 MAX 1.00 0.05 14º 0.30 2.70 1.75 0.50 VARIATION VEED-5 Dimensions in Inches Conversion Factor: 1 Inch = 25.40 mm MIN NOM MAX 0.032 0.036 0.039 0.000 0.001 0.002 0.008 REF 0.008 0º 14º 0.008 0.010 0.012 0.119 BSC 0.087 0.106 0.119 BSC 0.056 0.069 0.020 BSC 0.012 0.016 0.020 JL Aug09-05 / RevA SP6682 High Efficiency Charge Pump Regulator for White LEDs 11 © 2006 Sipex Corporation ORDERING INFORMATION Part Number Top Mark Operating Temperature Range Package Type SP6682EU ....................... SP6682EU....................................-40°C to +85°C ............................ 10 Pin MSOP SP6682EU/TR ................. SP6682EU....................................-40°C to +85°C ............................ 10 Pin MSOP SP6682ER ........................ SP6682ERYWW.........................-40°C to +85°C ................................ 10 Pin DFN SP6682ER/TR ................. SP6682ERYWW...........................-40°C to +85°C ............................... 10 Pin DFN Available in lead free packaging. To order add "-L" suffix to part number. Example: SP6682ER/TR = standard; SP6682ER-L/TR = lead free /TR = Tape and Reel Pack quantity is 2,500 for MSOP and 3,000 for DFN. Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600 Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. Date: 7/19/06 Rev D SP6682 High Efficiency Charge Pump Regulator for White LEDs 12 © 2006 Sipex Corporation