® SP6682 High Efficiency Charge Pump Regulator for White LEDs FEATURES ■ Ideal For White LED Driver ■ Low Profile, Inductorless Regulator ■ 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 ■ Built-in 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 VOUT 1 C1P 2 VIN 3 VMODE 4 FB 5 10 C2P 9 C1N SP6682 8 GND 10 Pin DFN 7 C2N 6 EN/PWM Now Available in Lead Free Packaging APPLICATIONS ■ Next Generation Mobile Phones ■ PDAs ■ 3.3V to 5.0V Conversion ■ Digital Still Cameras ■ Digital Camcorders ■ 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 LED used in backlighting color displays. The charge pump automatically switches between X1.5 and X2 modes based on the input voltage, providing improved efficiency over traditional methods using charge pump doubler followed by LDO. This input voltage threshold can be externally programmed for optimized efficiency at specific output voltages and currents. The SP6682 operates with an internal 600kHz clock, enabling the use of small external components. 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 C2 2.2µF ® 1 V OUT 2 C1P 2.7 - 4.2V Lithium-Ion R1 C1 2.2µF R2 ENABLE/PWM DIMMING Date: 5/5/04 C2P 10 SP6682 C1N 9 3 8 VIN GND 4 7 VMODE C2N 5 6 FB EN/PWM C6 0.1µF C4 2.2µF C5 2.2µF White LED R6 20 C3 0.1µF 20 20 20 R3 1M SP6682 High Efficiency Charge Pump Regulator for White LEDs 1 © Copyright 2004 Sipex Corporation ABSOLUTE MAXIMUM RATINGS VIN, VMODE, VOUT and EN/PWM ................. -0.3V to 6V VIN - VOUT ........................................................... 0.7V Output Current (IOUT) ...................................... 120mA 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=0.03Ω), 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 Ω FB = 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: 5/5/04 0.5 µA 0.4 V 0.5 µA VEN/PWM = 4.2V 0.5 µA VFB = 1V 500 µs VIN = 3.6V, FB within 90% regulation 1.6 VMODE = 1.25 V 0.01 FB Pin Current VOUT Turn-On Time EN/PWM = 0V, VIN = 5.5V VIN = 3.6V 175 SP6682 High Efficiency Charge Pump Regulator for White LEDs 2 © Copyright 2004 Sipex Corporation PIN DESCRIPTION PIN NUMBER PIN NAME 1 VOUT DESCRIPTION Regulated charge pump output. 2 C1P Positive terminal to the charge pump flying capacitor C2. 3 VIN Input pin for the 2.7V to 5.5V supply voltage. 4 VMODE Charge pump mode program pin. When VMODE is greater than 1.25V, X1.5 charge pump is used. Otherwise, charge pump switches to X2 mode. A voltage divider shown in typical application circuit programs the VIN threshold for charge pump mode switching. 5 FB This is the feedback pin for output current or voltage regulation. The voltage of this pin is compared with an internal 306mV reference. 6 EN/PWM Enable and PWM dimming control input. Pull this pin low to disconnect VOUT from VIN and shutdown the SP6682. 7 C2N Negative terminal to the charge pump flying capacitor, C4. 8 GND Ground reference. 9 C1N Negative terminal to the charge pump flying capacitor, C2. 10 C2P Positive terminal to the charge pump flying capacitor C4. FUNCTIONAL DIAGRAM VIN 600 kHz Clock Manager Voltage Referenc EN/PW 1.25V VMODE MODE COMP Mode Control C1P Start-up and Charge Pump Switches C1N C2P C2N VOUT 306m FB VOUT COMP GND Date: 5/5/04 SP6682 High Efficiency Charge Pump Regulator for White LEDs 3 © Copyright 2004 Sipex Corporation PERFORMANCE CHARACTERISTICS Refer to the typical application circuit, TAMB = 25°C, IO = 60mA unless otherwise specified. EN/PWM 90 5V/DIV 80 70 Efficiency (%) 1V/DIV VOUT 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 VFB (V) 0.32 VOUT 0.31 0.3 0.29 50mV/DIV 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: 5/5/04 Figure 6. Quiescent current vs. input voltage SP6682 High Efficiency Charge Pump Regulator for White LEDs 4 © Copyright 2004 Sipex Corporation PERFORMANCE CHARACTERISTICS: Continued Refer to the typical application circuit, TAMB = 25°C, IO = 60mA unless otherwise specified. 6 3 100 Hz Brigtness, kCd/m2 Brightness (kcd/m2) 5 4 3 2 1 0 2.7 500 Hz 2 1 0 3 3.3 3.6 3.9 4.2 0 20 Input Voltage (V) 4 LED's @ 30mA 40 60 80 100 Duty Cycle,% 4 LED's @ 15mA Figure 7. Brightness vs. input voltage Figure 8. Brightness vs duty cycle OPERATION General Overview parators (VMODE Comparator and VOUT Comparator). 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 in cellular phones, PDAs, digital cameras and MP3 players. The SP6682’s 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 shut down 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. 1) Voltage Reference. This block provides the 306mV and 1.25V reference voltages needed for the two comparators. 2) Mode Control. An external voltage divider connected to the VMODE pin will define 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 comparatorbased cycle by cycle 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, 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 LED from experi- Theory of Operation The SP6682 regulated charge pump block diagram consists of four main blocks (Voltage Reference, Mode Control, Clock Manager, Startup and Charge-Pump Switches) and two com- Date: 5/5/04 SP6682 High Efficiency Charge Pump Regulator for White LEDs 5 © Copyright 2004 Sipex Corporation OPERATION: Continued encing 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. back 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 5) VOUT Comparator and Output Control. A 306mV reference voltage is compared to feed- where VFB = 306mV. OUT RFB APPLICATION INFORMATION The current of the remaining white LEDs is set according to the similarity of the white LEDs. 3wire white LED module with internal series resistors as shown in figure 10 can also be driven in this way. Configuring the SP6682 as Voltage or Current Source 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 figure 9~12. Figure 9 shows using the SP6682 to drive discrete white LEDs as a current source. Anode FB 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: 3-wire W-LED module GND Fig 10. 3-wire white LED module In figure 11, 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 9. RB = VFB ILED VOUT VOUT 1 Anode 1 SP6682 FB 5 SP6682 2-wire W-LED module Rb GND Rb VFB GND 2.2uF 8 Cathode Rb 8 Figure 9. Driving discrete white LEDs as current source Date: 5/5/04 5 Figure 11. Driving 2-wire white LED module as current source SP6682 High Efficiency Charge Pump Regulator for White LEDs 6 © Copyright 2004 Sipex Corporation APPLICATION INFORMATION: Continued In this application, the bias resistor can be selected by: R = VFB 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 13. B ILED (TOTAL) where ILED(TOTAL) is the total operating current of all the white LEDs. 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 Vth threshold voltage, it will switch to X2 mode automatically. The Vth threshold voltage for mode change can be calculated by: To use SP6682 as a voltage source for fixed voltage applications, a voltage divider is need to program the ouput voltage, as shown in figure 12. The output voltage is set by the ratio of the two VOUT VTH = (VF + 0.306 + m • ILED • ROUT)/1.5 Anode 1 R5 SP6682 Where VF and m are the forward voltage and number of the white LEDs, Rout is the output resistance of the SP6682. 2.2uF VFB 5 R6 GND The equation for the voltage divider R1 and R2 with VMODE = 1.25V is: 2-wire W-LED module 8 Cathode VTH = 1.25V • (1+R1/R2) Figure 12. Driving 2-wire white LED module as voltage source which can be expressed as R1: resistors and the feedback control voltage as shown by: VOUT = ( 1 + R1 = (VTH / 1.25 -1) • R2 For the typical SP6682 application, Using VF=3.6V, m=4, ILED=15mA, ROUT=16Ω, the VTH will be 3.24V. Select R2=100kΩ, then R1=158kΩ. R5 ) • VFB R6 Capacitor Selection 3 VIN Ceramic capacitors are recommended for their inherently low ESR, which will help produce low peak to peak output ripple, and reduce high frequency spikes. VIN R1 4 SP6682 VMODE 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 capaci- R2 C2 GND 8 Figure 13. Programming the Vmode Resistors Date: 5/5/04 SP6682 High Efficiency Charge Pump Regulator for White LEDs 7 © Copyright 2004 Sipex Corporation APPLICATION INFORMATION tor leads to larger output resistance, thus decreasing the output 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. Refer to Table 1 for some suggested low ESR capacitors. Table: 1 SUGGESTED LOW ESR CAPACITORS MANUFACTURERS/ TELEPHONE# PART NUMBER CAPACITANCE/ VOLTAGE CAPACITOR/ SIZE/TYPE ESR AT 100kHz TDK/847-803-6100 C2012X5R1A225K 2.2µF/10V 0805/X5R 0.030Ω TDK/847-803-6100 C2012X5R0J475K 4.7µF/6.3V 0805/X5R 0.020Ω MURATA/770-436-1300 GRM188R60J225KE01D 2.2µF/6.3V 0603/X5R 0.030Ω MURATA/770-436-1300 GRM219R60J475KE01D 4.7µF/6.3V 0805/X5R 0.020Ω Brightness Control Using PWM tional to the operating current, for better brightness matching, a higher output voltage could be used. This could be done by using larger resistor, as shown in figure 14. Rb2 is used to bias the operating current of the white LED, Rb1 is use to increase the output voltage. Better brightness matching was achived 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. VOUT 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 tolerance, thus causing uneven brightness of the white LEDs. I2 In D1 D2 Dn VF1 VF2 VFn Rb1 5 VFB Rb Rb Rb2 GND 8 Rb Figure 14. Increasing brightness matching Power Efficiency = VOUT - VF1 VOUT - VF2 The efficiency of driving the white LEDs can be calculated by: where I1 I2 are the operating current of the white LEDs,VF1,VF2 are the forward voltage of the white LEDs. VF • IF VF η = VF • IF = ≈ Vi • Ii Vi • (n • IF + IQ) Vi • n Since the brightness of the white LED is proporDate: 5/5/04 I2 I1 SP6682 In figure 14, assume high-precision bias resistors were used, the operating current ratio of two different branches can be easily derived as shown by: I1 1 SP6682 High Efficiency Charge Pump Regulator for White LEDs 8 © Copyright 2004 Sipex Corporation APPLICATION INFORMATION 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. this application as well as actual data showing efficiency of > 85%. By using an external inductor, MOSFET and diode, high output voltage 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: n is the boost ratio (X1.5 or X2) 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 15 shows the schematic of L1 LQH32CN4R7M11 DS SCHOTTKY MBR0530 SP6682 3 4 C1 5 C2P C1P C1N VIN GND VMODE FB C2N EN/PWM 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 R3 1M 10uF X5R Ceramic D7 Efficiency (%) 2 Vin: 2.7-4.2V VOUT D1 EN/PWM VFB R1 100 ILED = VFB/R1 = 20mA 4.7uH 1 ILED = 90 85 80 75 R1 15 R2 15 70 2.7 3.0 3.3 3.6 3.9 4.2 VIN (V) Figure 15. Using SP6682 as a High Voltage White LED Driver PINOUTS VOUT 1 10 C2P VOUT 1 C1P 2 9 C1N C1P 2 VIN 3 8 GND VIN 3 VMODE 4 FB 5 Date: 5/5/04 SP6682 10 Pin DFN 7 C2N VMODE 4 6 EN/PWM 10 C2P SP6682 8 GND 10 Pin MSOP FB 5 SP6682 High Efficiency Charge Pump Regulator for White LEDs 9 9 C1N 7 C2N 6 EN/PWM © Copyright 2004 Sipex Corporation PACKAGE: 10 PIN MSOP (ALL DIMENSIONS IN MILLIMETERS) D e1 Ø1 E/2 R1 R E1 E Gauge Plane L2 Ø1 Seating Plane Ø L L1 1 2 e Pin #1 indentifier must be indicated within this shaded area (D/2 * E1/2) Dimensions in (mm) 10-PIN MSOP JEDEC MO-187 (BA) Variation MIN NOM MAX A - - 1.1 A1 0 - 0.15 A2 0.75 b 0.17 - 0.27 c 0.08 - 0.23 D 0.85 0.95 (b) WITH PLATING 3.00 BSC E 4.90 BSC E1 3.00 BSC e 0.50 BSC e1 c 2.00 BSC L 0.4 0.60 0.80 L1 - 0.95 - L2 - 0.25 - N - 10 - R 0.07 - - R1 0.07 - Ø 0º Ø1 0º BASE METAL D A2 - A 8º - b 15º A1 1 Date: 5/5/04 SP6682 High Efficiency Charge Pump Regulator for White LEDs 10 © Copyright 2004 Sipex Corporation PACKAGE: 10 PIN DFN Bottom View Top View D e b D/2 1 2 E/2 E2 E K L D2 Pin 1 identifier to be located within this shaded area. Terminal #1 Index Area (D/2 * E/2) 10 Pin DFN DIMENSIONS in (mm) (JEDEC MO-229, VEED-5 VARIATION) SYMBOL A A1 A3 b D D2 e E E2 K L MIN NOM MAX 0.80 0 0.90 1.00 0.02 0.05 0.20 REF A 0.18 0.25 0.30 3.00 BSC 2.20 2.70 0.50 PITCH 3.00 BSC 1.40 1.75 0.20 - 0.50 0.30 0.40 A1 A3 Side View 10 PIN DFN Date: 5/5/04 SP6682 High Efficiency Charge Pump Regulator for White LEDs 11 © Copyright 2004 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 ....................... SP6682EURYWW.........................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. Corporation ANALOG EXCELLENCE 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: 5/5/04 SP6682 High Efficiency Charge Pump Regulator for White LEDs 12 © Copyright 2004 Sipex Corporation