S P6685 700mA Buck/Boost Charge Pump LED Driver June 2009 Rev. 2.0.0 GENERAL DESCRIPTION APPLICATIONS The SP6685 is a current-regulated charge pump ideal for powering high brightness LEDs for camera flash applications. The charge pump can be set to regulated two current levels for FLASH and TORCH modes. The SP6685 automatically switches modes between step-up and step-down ensuring that LED current does not depend on the forward voltage. A low current sense reference voltage (50mV) allows the use of small 0603 current sensing resistors. The SP6685 is designed to operate from a single cell lithium-ion battery or fixed 3.3V or 5.0V power rails and is available in a RoHS compliant, “green”/halogen free space saving 10-pin 3mmx3mm DFN package. • White LED Torch/Flash for Cell Phone, DSCs and Camcorders • White LED Backlighting • Generic Lighting/Flash Application • General Purpose High Current Boost FEATURES • Output Current up to 700mA • Up to 94% Efficiency in Torch Mode • Minimum External Components: No Inductor • Adjustable FLASH Mode Current • 1x and 2x Charge Pump Operation • 2.4MHz High Frequency Operation • IQ < 1µA in Shutdown • Built-In Soft Start Limit Inrush Current • Output Overvoltage Protection • Over current/Temperature Protection • 10pin 3x3mm DFN Package TYPICAL APPLICATION DIAGRAM Fig. 1: SP6685 Application Diagram Exar Corporation 48720 Kato Road, Fremont CA 94538, USA www.exar.com Tel. +1 510 668-7000 – Fax. +1 510 668-7001 S P6685 700mA Buck/Boost Charge Pump LED Driver ABSOLUTE MAXIMUM RATINGS OPERATING RATINGS 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. Input Voltage Range VIN ............................... 2.7V to 5.5V Operating Temperature Range ................... -40°C to 85°C Thermal Resistance θJA ................................... 57.1°C/W VIN, VOUT ................................................... -0.3V to 6.0V Output Current Pulse (FLASH) .................................... 1A Output Current Continuous (TORCH) ........................ 0.4A VEN ................................................................. 0V to 7V Storage Temperature .............................. -65°C to 150°C Lead Temperature (Soldering, 10 sec) ................... 260°C ESD Rating EN pin (HBM - Human Body Model) .......... 1kV ESD Rating All Other Pins (HBM) .............................. 2kV ELECTRICAL SPECIFICATIONS Specifications with standard type are for an Operating Junction Temperature of TJ = 25°C only; limits applying over the full Operating Junction Temperature range are denoted by a “•”. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Unless otherwise indicated, VIN = 3.6, CIN = 4.7µF, CFC = COUT = 1µF. TA= –40°C to 85°C. Parameter Operating Input Voltage Min. Typ. 2.7 0.5 Quiescent Current Max. Units 5.5 V 3 mA Conditions • • 2 Shutdown Current FLASH = VIN, 2x Mode 1 Oscillator Frequency VIN = 2.7 – 5.5V FLASH = 0V ILOAD = 100 µA µA VIN = 5.5V, VEN = 0V 2.4 MHz Charge Pump Equivalent Resistance (x2 Mode) 5 Ω VFB = 0V, VIN = 3.6V Charge Pump Equivalent Resistance (x1 Mode) 0.6 0.8 Ω VIN = 3.6V FB Reference Voltage 138 150 162 mV • FLASH = VIN, RSET = 88.7K FB Reference Voltage 45 50 55 mV • FLASH = GND FB Pin Current 0.5 µA EN, Flash Logic Low 0.4 V V • 0.5 µA • 500 µS • EN, Flash Logic High 1.3 EN, Flash Pin Current VOUT Turn-on Time 250 Thermal Shutdown Temperature 145 © 2009 Exar Corporation VFB = 0.3V • VIN = 3.6V, FB within 90% of regulation o C 2/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver BLOCK DIAGRAM Fig. 2: SP6685 Block Diagram PIN ASSIGNEMENT Fig. 3: SP6685 Pin Assignment © 2009 Exar Corporation 3/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver PIN DESCRIPTION Name Pin Number Description VIN 1 Input voltage for the charge pump. Decouple with 4.7µF ceramic capacitor close to the pins of the IC. C1 2 Positive input for the external fly capacitor. Connect a ceramic 1µF capacitor close to the pins of the IC. C2 3 Negative input for the external fly capacitor. Connect a ceramic 1µF capacitor close to the pins of the IC. FLASH 4 Logic input to toggle between FLASH and TORCH mode. In TORCH Mode FB is regulated to the internal 50mV reference. In FLASH Mode FB reference voltage can be adjusted by changing the resistor from RSET pin to ground. Choose the external current sense Resistor (RSENSE) based on desired current in TORCH Mode. EN 5 Shutdown control input. Connect to VIN for normal operation, connect to ground for shutdown. RSET 6 Connect a resistor from this pin to ground. When in FLASH Mode (FLASH = High) this resistor sets the current regulation point according to the following: VFB = (1.26V/RSET)*11.2KΩ FB 7 Feedback input for the current control loop. Connect directly to the current sense resistor. SGND 8 Internal ground pin. Control circuitry returns current to this pin. PGND 9 Power ground pin. Fly capacitor current returns through this pin. VOUT 10 Charge Pump Output Voltage. Decouple with an external capacitor. At least 1µF is recommended. Higher capacitor values reduce output ripple. ORDERING INFORMATION Temperature Range Marking Package Packing Quantity SP6685ER-L -40°C≤TA≤+85°C SP66 85ER WWX DFN-10 Bulk RoHS Compliant Halogen Free SP6685ER-L/TR -40°C≤TA≤+85°C SP66 85ER WWX DFN-10 3K/Tape & Reel RoHS Compliant Halogen Free Part Number SP6685EB Note 1 Note 2 SP6685 Evaluation Board “WW” = Work Week – “X” = Lot Number © 2009 Exar Corporation 4/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver TYPICAL PERFORMANCE CHARACTERISTICS All data taken at VIN = 3.6V, Typical Application Circuit, D1 = Luxeon LXCL-PWF1, TJ = TA = 25°C, unless otherwise specified. Fig. 4: TORCH Mode Output Current Fig. 5: FLASH Mode Output Current Fig. 6: TORCH Mode Output Efficiency Fig. 7: FLASH Mode Output Efficiency Fig. 8: Ripple 1x FLASH Mode 700mA, CH1 = VIN CH2 = VOUT, VIN = 4.2V, CIN = 10µF, CF = 1µF, COUT = 4.7µF © 2009 Exar Corporation Fig. 9: Ripple 2x FLASH Mode 700mA. CH1 = VIN CH2 = VOUT, VIN = 3.6V, CIN = 10µF, CF = 1µF, COUT = 4.7µF 5/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver Fig. 10: Ripple 1x TORCH Mode 200mA. CH1 = VIN CH2 = VOUT, VIN = 4.2V, CIN = 10µF, CF = 1µF, COUT = 4.7µF Fig. 11: Ripple 2x TORCH Mode 200mA. CH1 = VIN CH2 = VOUT, VIN = 3.0V, CIN = 10µF, CF = 1µF, COUT = 4.7µF Fig. 12: COUT = 4.7µF Fig. 13: COUT = 4.7µF Fig. 14: CIN = 10µF Fig. 15: CIN = 10µF © 2009 Exar Corporation 6/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver Fig. 16: Output Current vs Supply Voltage Fig. 17: Efficiency ve Supply Voltage Fig. 18: Battery Current vs Supply Voltage Fig. 18: D1 = AOT 3228HPW0303B LED, RSENSE = 0.33Ω RSET = 162K, CIN = 4.7µF, CF = 0.47µF, COUT = 1µF Fig. 20: D1 = AOT 3228HPW0303B LED, RSENSE = 0.33Ω RSET = 162K, CIN = 4.7µF, CF = 0.47µF, COUT = 1µF Fig. 21: D1 = AOT 3228HPW0303B LED, RSENSE = 0.33Ω RSET = 162K, CIN = 4.7µF, CF = 0.47µF, COUT = 1µF © 2009 Exar Corporation 7/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver Fig. 22: D1 = AOT 6060HPW0305B LED, RSENSE = 0.33Ω RSET = 75K, CIN = 4.7µF, CF = 1µF, COUT = 1µF Fig. 23: D1 = AOT 6060HPW0305B LED, RSENSE = 0.33Ω RSET = 75K, CIN = 4.7µF, CF = 1µF, COUT = 1µF Fig. 19: D1 = AOT 6060HPW0305B LED, RSENSE = 0.33Ω RSET = 75K, CIN = 4.7µF, CF = 1µF, COUT = 1µF Fig. 20: D1 = AOT 2015HPW1915B LED, RSENSE = 0.22Ω RSET = 80.6K, CIN = 4.7µF, CF = 1µF, COUT = 1µF Fig. 26: D1 = AOT 2015HPW1915B LED, RSENSE = 0.22Ω RSET = 80.6K, CIN = 4.7µF, CF = 1µF, COUT = 1µF Fig. 27: D1 = AOT 2015HPW1915B LED, RSENSE = 0.22Ω RSET = 80.6K, CIN = 4.7µF, CF = 1µF, COUT = 1µF © 2009 Exar Corporation 8/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver Fig. 28: Startup 200mA Torch VIN = 3.6V, VOUT = 3.2V Fig. 29: Startup 700mA Flash VIN = 3.6V, VOUT = 3.6V Fig. 30: Torch in 1X to Flash in 1X Mode, VIN = 4.2V CH1 = FLASH, CH2 = VOUT, CH3 = VFB, CH4 = IOUT 1A/div Fig. 31: Torch in 1X to Flash in 2X Mode, VIN = 3.6V CH1 = FLASH, CH2 = VOUT, CH3 = VFB, CH4 = IOUT 1A/div Fig. 32: Efficiency See fig.34 for Application Circuit Fig. 33: Output Current See fig.34 for Application Circuit © 2009 Exar Corporation 9/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver APPLICATION INFORMATION The SP6685 can be used with multiple LEDs in parallel as shown in figure 34. For best performance, the LEDs should be in a single package, preferably from a single die to have better matching for forward voltage Vf for a given forward current If. In practice, if the Vf of one LED is higher than the others, it will consume a larger If, which will raise its temperature which will then cause its Vf to reduce, correcting the imbalance. The overall current will be the sum of the individual currents, for example Itotal = 4*ILED. Fig. 34: Multiple LED Flash Circuit THEORY OF OPERATION which acts like a linear regulator to control the output current by continuously monitoring the feedback pin FB. In 1X mode, if the SP6685 auto detects a dropout condition, which is when the FB pin is below the regulation point for more than 32 cycles of the internal clock, the SP6685 automatically switches to the 2X mode. The SP6685 remains in the 2X mode until one of four things happens: 1) the enable pin EN has been toggled, 2) the Flash pin has changed from High to Low, 3) VIN is cycled. 4) a thermal fault occurs. The SP6685 is a charge pump regulator designed for converting a Li-Ion battery voltage of 2.7V to 4.2V to drive a white LED used in digital still camera Flash and Torch applications. The SP6685 has two modes of operation which are pin selectable for either Flash or Torch. Flash mode is usually used with a pulse of about 200 to 300 millisecond to generate a high intensity Flash. Torch can be used continuously at a lower output current than Flash and is often used for several seconds in a digital still camera “movie” mode. The 2X mode is the charge pump mode where the output can be pumped as high as two times the input voltage, provided the output does not exceed the maximum voltage for the SP6685, which is internally limited to about 5.5V. In the 2X mode, as in the 1X mode, the output current is regulated by the voltage at the FB pin. The SP6685 also has two modes of operation to control the output current: the 1X mode and 2X mode. Operation begins after the enable pin EN receives a logic high, the bandgap reference wakes up after about 200µsec, and then SP6685 goes through a soft-start mode designed to reduce inrush current. The SP6685 starts in the 1X mode, © 2009 Exar Corporation 10/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver In the Torch mode, (Flash = GND) the Flash pin is set to logic low and the SP6685 IFB pin regulates to 50mV output: VFB = 50mV current exceeds approximately 1Amp, then the over current protection circuitry shuts off the output switches to protect the chip. COMPONENT SELECTION (Torch Mode) The SP6685 charge pump circuit requires 3 capacitors: 4.7µF input, 1μF output and 1μF fly capacitor are typically recommended. For the input capacitor, a larger value of 10μF will help reduce input voltage ripple for applications sensitive to ripple on the battery voltage. All the capacitors should be surface mount ceramic for low lead inductance necessary at the 2.4MHz switching frequency of the SP6685 and to obtain low ESR, which improves bypassing on the input and output and improves output voltage drive by reducing output resistance. Ceramic capacitors with X5R or X7R temperature grade are recommended for most applications. A selection of recommended capacitors is included in Table 1 below. When in Flash mode, (Flash = VIN), the FB regulation voltage is set by the resistor RSET connected between the RSET pin and SGND and the equation: VFB = (1.26V/ RSET)*11.2KΩ (Flash Mode) Where the 1.26V is the internal bandgap reference voltage and the 11.2KΩ is an internal resistance used to scale the RSET current. Typical values of RSET are 40KΩ to 180KΩ for a range of VFB = 300mV to 75mV in Flash mode. The output current is then set in either Flash or Torch mode by the equation: IOUT = VFB / Rsense Manufacturer Part Number Value Size/Type muRata GRM155R60J105K 1µF/6.3V 0402/X5R muRata GRM188R60J475K 4.7µF/6.3V 0603/X5R muRata GRM21BR60J106K 0805/X5R 10µF/6.3V Table 1: Recommended Capacitors OVERTEMPERATURE PROTECTION The input and output capacitors should be located as close to the VIN and VOUT pins as possible to obtain best bypassing, and the returns should be connected directly to the PGND pin or to the thermal pad ground located under the SP6685. The fly capacitor should be located as close to the C1 and C2 pins as possible. See typical circuit layout (page 13) for details on the recommended layout. When the temperature of the SP6685 rises above 145°C, the over temperature protection circuitry turns off the output switches to prevent damage to the device. If the temperature drops back down below 135°C, the part automatically recovers and executes a soft start cycle. OVERVOLTAGE PROTECTION The SP6685 has over voltage protection. If the output voltage rises above the 5.5V threshold, the over voltage protection shuts off all of the output switches to prevent the output voltage from rising further. When the output decreases below 5.5V, the device resumes normal operation. To obtain lower output ripple, the COUT value can be increased from 1μF to 2.2μF or 4.7μF with a corresponding decrease in output ripple as shown in the Typical Performance Characteristic curves. For output currents of 500mA to 700mA, the recommended CFC fly capacitor value of 1μF should be used. Output currents in Flash of 100mA to 400mA can use a 0.47μF CFc but a minimum 1μF COUT is still needed. OVERCURRENT PROTECTION The over current protection circuitry monitors the average current out of the VOUT = 50mV (Torch Mode) pin. If the average output © 2009 Exar Corporation 11/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver range of typical resistor values and sizes are shown in table 2. RESISTOR SELECTION The sense resistor RSENSE is determined by the value needed in the Torch mode for the desired output current by the equation: RSENSE = VFB/IOUT Where VFB = 50mV (Torch Mode) Once the RSENSE resistor has been selected for Torch mode, the VFB voltage can be selected for Flash mode using the following equation: VFB = IOUT * RSENSE (Flash Mode) Where IOUT is for Flash Mode. Next, the RSET resistor can be selected for Flash mode using the following equation: RSET = (1.26V/ VFB)*11.2KΩ (Flash Mode) Part Ref. Value Tolerance Size RSET 68KΩ 5% 0402 RSET 75KΩ 5% 0402 RSET 82KΩ 5% 0402 RSET 91KΩ 5% 0402 RSET 100KΩ 5% 0402 RSET 110KΩ 5% 0402 RSET 120KΩ 5% 0402 RSET 130KΩ 5% 0402 RSET 140KΩ 5% 0402 RSET 150KΩ 5% 0402 RSENSE 0.22Ω 5% 0603 RSENSE 0.27Ω 5% 0603 RSENSE 0.33Ω 5% 0603 RSENSE 0.39Ω 5% 0603 RSENSE 0.47Ω 5% 0603 Table 2: Resistor Value and Sizes For an example of 200mA Torch mode and 600mA Flash mode, the values RSENSE = 0.25Ω, VFB = 150mV (Flash Mode), and RSET = 94KΩ are calculated. The power obtained in the Flash mode would be: EVALUATION BOARD CIRCUIT LAYOUT PFLASH = VFB *IOUT = 150mV*600mA = 90mW. The typical 0603 surface mount resistor is rated 1/10 Watt continuous power and 1/5 Watt pulsed power, more than enough for this application. For other applications, the PFLASH power can be calculated and resistor size selected. The RSENSE resistor is recommended to be size 0603 for most applications. The © 2009 Exar Corporation 12/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver PACKAGE SPECIFICATION 10-PIN DFN © 2009 Exar Corporation 13/14 Rev. 2.0.0 S P6685 700mA Buck/Boost Charge Pump LED Driver REVISION HISTORY Revision 2.0.0 Date 06/18/2009 Description Reformatted to corporate standard Updated ESD level for EN pin. FOR FURTHER ASSISTANCE Email: [email protected] Exar Technical Documentation: http://www.exar.com/TechDoc/default.aspx? EXAR CORPORATION HEADQUARTERS AND SALES OFFICES 48720 Kato Road Fremont, CA 94538 – USA Tel.: +1 (510) 668-7000 Fax: +1 (510) 668-7030 www.exar.com NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user’s specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. or its in all Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited. © 2009 Exar Corporation 14/14 Rev. 2.0.0