® Preliminary SP6683 High Power LED Driver for Parallel Configuration FEATURES VOUT 1 10 C2P ■ Drives up to 8 WLEDS ■ Low Profile Inductorless Regulator C1P 2 SP6683 9 C1N ■ 1x/1.5x Mode Charge Pump 8 GND VIN 3 ■ 200mA Output Using 1µF Ceramic Caps 10 Pin DFN 7 C2N VMODE 4 ■ +2.7V to +5.5V Input Voltage Range 6 EN/PWM FB 5 ■ 0.9mA Quiescent Current ■ 1µA Shutdown Current Now Available in Lead Free Packaging ■ Built-in 1.2MHz Oscillator ■ Programmable Output Current or Voltage APPLICATIONS ■ PWM Dimming Control via Enable Pin ■ Mobile Phone ■ Shutdown to Disconnect Output from Input ■ PDA via Shutdown ■ Digital Still Camera ■ Soft Start to limit In-Rush Current ■ Digital Camcorder ■ Space Saving 10-pin 3 x 3mm DFN Package ■ Palmtop Computer ■ Color LCD Module DESCRIPTION The SP6683 is a high power current regulated charge pump ideal for converting a Li-Ion battery input for driving up to 8 white LED’s used in backlighting color displays. The SP6683 operates with an internal 1.2MHz clock, enabling the use of small external components. Output current can be accurately regulated by modulating the switcher between the charge pump and output capacitor. In shutdown mode, the SP6683 discharges the output to ground and draws less than 1µA current. The SP6683 utilizes 1µF capacitors to deliver up to 200mA current regulated WLED drive capability. The SP6683 is offered in 10-pin DFN or MSOP package. TYPICAL APPLICATION SCHEMATIC C2 1µF Lithium-Ion ® 1 V OUT 2 C1P R1 C1 1µF R5 ENABLE/PWM DIMMING Date: 07/07/04 C2P 10 SP6683 C1N 9 3 8 VIN GND 4 7 VMODE C2N 5 6 FB EN/PWM C4 1µF C5 1µF White LED C3 0.1µF R5 1M SP6683 White LEDs Driver for Parallel Configuration 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) ...................................... 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=1.0µF (Ceramic, ESR=0.03Ω) and TAMB =-40°C to +85°C unless otherwise noted. PARAMETER MIN Input Voltage 2.7 MAX UNITS 5.5 V 0.9 3 mA VIN = 4.2V, VOUT = 3.6V, IOUT = 100µA Shutdown Current 1.0 1.5 µA VEN/PWM = 0V, VIN = 5.5V Maximum Load Current 280 mA VIN = 4.2V, VOUT = 3.6V Quiescent Current Oscillator Frequency VFB Reference Voltage 0.8 1.2 1.6 MHz 0.275 0.306 0.337 V Output Resistance VMODE Threshold Voltage TYP 7.5 5 1.15 1.25 VMODE Hysteresis 30 VMODE Pin Current 0.01 EN/PWM Logic Low EN/PWM Logic High EN/PWM Pin Current VIN = 3.6V Ω Ω 1.5X Mode, 100mA Load 1.0X Mode, 100mA Load V VIN Falling @ 25°C mV VIN = 3.6V @ 25°C 0.5 µA VMODE = 1.25 V 0.4 V 1.6 V 0.01 FB Pin Current VOUT Ripple 80 VOUT Turn-On Time 175 Date: 07/07/04 1.35 CONDITIONS 0.5 µA VEN/PWM = 4.2V 0.5 µA VFB = 1V mV VIN = 5V, VOUT = 4V, IOUT = 100mA , 1.5x Mode µs VIN = 3.6V, FB within 90% regulation 500 SP6683 White LEDs Driver for Parallel Configuration 2 © Copyright 2004 Sipex Corporation PIN DESCRIPTION PIN NUMBER PIN NAME DESCRIPTION 1 VOUT Regulated charge pump output. 2 C1P Positive terminal to the charge pump flying capacitor C2. 3 VIN Input supply voltage. 4 VMODE 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 SP6683.VOUT is pulled to ground in shutdown. 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. Charge pump mode program pin. When VMODE is greater than 1.25V, a X1 charge pump is used. Otherwise, charge pump switches to X1.5 mode. A voltage divider shown in typical application circuit programs the VIN threshold for charge pump mode switching. FUNCTIONAL DIAGRAM VIN 1.2 MHz Clock Manager Voltage Reference EN/PWM 1.25V VMODE MODE COMP Mode Control C1P Start-up and Charge Pump Switches C1N C2P C2N VOUT 306mV FB VOUT COMP GND Date: 07/07/04 SP6683 White LEDs Driver for Parallel Configuration 3 © Copyright 2004 Sipex Corporation OPERATION General Overview 4) 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 The SP6683 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 SP6683 is able to efficiently drive up to eight 20mA white LEDs in parallel and maintain a constant brightness over a very wide operating voltage range (2.7V to 5.5V). The SP6683 operates with an internal 1.2MHz clock, enabling the use of small external components. Other features of SP6683 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 switch between the charge pump and output capacitor. OUT RFB where VFB = 306mV. Configuring the SP6683 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 SP6683 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 SP6683 to drive discrete whiteLEDs as a current source. Theory of Operation The SP6683 regulated charge pump block diagram consists of four main blocks (Voltage Reference, Mode Control, Clock Manager, Startup and Charge-Pump Switches) and two comparators (VMODE Comparator and VOUT Comparator). VOUT SP6683 1) Voltage Reference. This block provides the 306mV and 1.25V reference voltages needed for the two comparators. FB 5 Rb 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 X1 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. GND Rb 1uF 8 Figure 9. Driving discrete white LEDs as current source 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: RB = VFB ILED 3) Clock Manager. An internal 1.2MHz 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. Date: 07/07/04 1 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 SP6683 White LEDs Driver for Parallel Configuration 4 © Copyright 2004 Sipex Corporation OPERATION: Continued in this way. Anode In this application, the bias resistor can be selected by: R = VFB FB B ILED (TOTAL) 3-wire W-LED module where ILED(TOTAL) is the total operating current of all the white LEDs. GND Fig 10. 3-wire white LED module In figure 11, SP6683 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. VOUT To use SP6683 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 resistors and the feedback control voltage as shown by: Anode 1 VOUT = ( 1 + R5 ) • VFB R6 SP6683 VOUT 2-wire W-LED module VFB GND 5 R5 Cathode SP6683 1uF VFB Rb 5 R6 8 GND 8 2-wire W-LED module Cathode Figure 11. Driving 2-wire white LED module as current source Date: 07/07/04 Anode 1 Figure 12. Driving 2-wire white LED module as voltage source SP6683 White LEDs Driver for Parallel Configuration 5 © Copyright 2004 Sipex Corporation APPLICATION INFORMATION PROGRAMMING THE OPERATING MODE SP6683 can automatically change from X1 mode to X1.5 mode for highest efficiency. To use this feature, divider resistors should be chosen according to the specific application, as shown in figure 13. Which can be expressed as R1: R1 = VTH/1.25 - 1) • R2 For the typical SP6683 application, using VF = 3.6V, m = 8, ILED = 15mA, ROUT = 6Ω, VTH will be 4.63V, Select R2 = 100kΩ, then R1 = 270kΩ 3 VIN VIN R1 4 SP6683 Capacitor Selection VMODE R2 Ceramic capacitors are recommended for their inherently low ESR, which will help produce low peak to peak output ripple, and reduce high frequency spikes. C2 GND 8 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 capacitor leads to larger output resistance, thus decreasing the output current capability and the circuit efficiency. Place all the capacitors as close to the SP6683 as possible for layout. Increasing the value of the input and otput capicitors could further reduce the input and output ripple. Figure 13. Programming the Vmode Resistors The guideline for divider resistor selections is as follows. For high input voltage, the SP6683 will work in X1 mode. When the input voltage drops to Vth threshold voltage, it will switch to X1.5 mode automatically. The Vth threshold voltage for mode change can be calculated by: VTH = (VF + 0.306 + m • ILED • ROUT) Where VF and m are the forward voltage and number of the white LEDs, Rout is the output resistance of the SP6683. Refer to table 1 for some suggested low ESR capicitors. The equation for the voltage divider R1 and R2 with VMODE = 1.25V is: VTH = 1.25V • (1+R1/R2) 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 Date: 07/07/04 SP6683 White LEDs Driver for Parallel Configuration 6 © Copyright 2004 Sipex Corporation APPLICATION INFORMATION: Continued 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 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. Brightness Control Using PWM Dimming control can be achieved by applying a PWM contol 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 operating frequency range is from 60Hz to 700Hz, the recomended maxium brightness frequncy range is from 60Hz to 200Hz. A repition rate of at least 60Hz is required to prevent flicker. Power Efficiency The efficiency of driving the white LEDs can be calculated by 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. VF • I F VF η = VF • IF = ≈ V i • Ii Vi • (n • IF + IQ) Vi • n 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. 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 I2 = VOUT - VF1 VOUT - VF2 where I1 I2 are the operating current of the white LEDs,VF1,VF2 are the forward voltage of the white LEDs. VOUT 1 I2 I1 In D1 D2 Dn VF1 VF2 VFn SP6683 Rb1 5 VFB Rb Rb Rb2 GND 8 Rb Figure 14. Increasing brightness matching Date: 07/07/04 SP6683 White LEDs Driver for Parallel Configuration 7 © Copyright 2004 Sipex Corporation PACKAGE: 10 PIN DFN D D/2 A3 E/2 E Top View A1 A Side View D2 2 1 10 Pin DFN DIMENSIONS in (mm) (JEDEC MO-229, VEED-5 VARIATION) E2 SYMBOL A A1 A3 b D D2 e E E2 K L K L e b Bottom View MIN NOM MAX 0.80 0 0.90 1.00 0.02 0.05 0.20 REF 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 0.30 0.40 0.50 10 Pin DFN Date: 07/07/04 SP6683 White LEDs Driver for Parallel Configuration 8 © Copyright 2004 Sipex Corporation PACKAGE: 10 PIN MSOP D e1 Ø1 E/2 R1 R E1 E L2 Ø1 Seating Plane L Gauge Plane Ø 00 L1 1 2 e Pin #1 indentifier must be indicated within this shaded area (D/2 * E1/2) 10-PIN MSOP JEDEC MO-187 (BA) Variation A Dimensions in (mm) MIN - 0.00 A1 1.10 - 0.75 b 0.17 - 0.27 c 0.08 - 0.23 0.85 B 0.15 A2 D B NOM MAX - 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 REF L2 0.25 BSC N BASE METAL Section B-B 10 R 0.07 - - R1 0.07 - - Ø 0º Ø1 5º - A2 A 8º b 15º A1 10-PIN MSOP 1 Date: 07/07/04 SP6683 White LEDs Driver for Parallel Configuration 9 © Copyright 2004 Sipex Corporation ORDERING INFORMATION Part Number Operating Temperature Range SP6683ER .................................................. SP6683ER/TR ............................................ SP6683EU .................................................. SP6683EU/TR ............................................ Package Type -40°C to +85°C ........................................................... 10 Pin DFN -40°C to +85°C ........................................................... 10 Pin DFN -40°C to +85°C ........................................................ 10 Pin MSOP -40°C to +85°C ........................................................ 10 Pin MSOP Available in lead free packaging. To order add "-L" suffix to part number. Example: SP6683ER/TR = standard; SP6683ER-L/TR = lead free /TR = Tape and Reel Pack quantity is 3000 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: 07/07/04 SP6683 White LEDs Driver for Parallel Configuration 10 © Copyright 2004 Sipex Corporation