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| S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver August 2009 Rev. 2.0.0 GENERAL DESCRIPTION The SP6686 is a current-regulated charge pump ideal for powering high brightness LEDs for camera flash applications. The charge pump can be set to regulate two current levels for FLASH and TORCH modes. The SP6686 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 SP6686 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 APPLICATIONS * White LED Torch/Flash for Mobile Phones, DSCs and Camcorders * Generic Lighting/Flash/Strobe Applications * White LED Backlighting FEATURES * Output Current up to 400mA * Up to 94% Efficiency in Torch Mode * Adjustable FLASH Mode * x1 and x2 Automatic Modes for High Efficiency * Minimum External Components: No Inductors * 2.4MHz High Frequency Operation * 1A Shutdown Current * Built-In Soft Start Limit Inrush Current * Output Overvoltage Protection * Over current/Temperature Protection * 10-pin 3mm x 3mm DFN Package TYPICAL APPLICATION DIAGRAM Fig. 1: SP6686 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 P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver ABSOLUTE MAXIMUM 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. VIN, VOUT ................................................... -0.3V to 6.0V Output Current Pulse (FLASH) .............................. 500mA Output Current Continuous (TORCH) ..................... 200mA VEN ................................................................. 0V to 7V Storage Temperature .............................. -65C to 150C Lead Temperature (Soldering, 10 sec) ................... 260C ESD Rating EN pin (HBM - Human Body Model) .......... 1kV ESD Rating All Other Pins (HBM) .............................. 2kV OPERATING RATINGS Input Voltage Range VIN ............................... 2.7V to 5.5V Operating Temperature Range ................... -40C to 85C Thermal Resistance JA ................................... 57.1C/W ELECTRICAL SPECIFICATIONS Specifications with standard type are for an Operating Junction Temperature of TJ = 25C 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 = 25C, and are provided for reference purposes only. Unless otherwise indicated, VIN = VSHTDN= 3.6V, CIN = 2.2F, CFC = 0.47F, COUT = 1F. TA= -40C to 85C. Parameter Operating Input Voltage Quiescent Current Shutdown Current Oscillator Frequency Charge Pump Equivalent Resistance (x2 Mode) Charge Pump Equivalent Resistance (x1 Mode) FB Reference Voltage FB Reference Voltage FB Pin Current EN, Flash Logic Low EN, Flash Logic High EN, Flash Pin Current VOUT Turn-on Time Thermal Shutdown Temperature 250 145 1.3 0.5 500 138 45 2.4 5 0.6 150 50 0.8 162 55 0.5 0.4 Min. 2.7 0.5 2 1 A MHz Typ. Max. 5.5 3 Units V mA * * VIN = 2.7 - 5.5V FLASH = 0V ILOAD = 100 A FLASH = VIN, 2x Mode VIN = 5.5V, VEN = 0V VFB = 0V, VIN = 3.6V VIN = 3.6V * * * * * * VIN = 3.6V, FB within 90% of regulation FLASH = VIN, RSET = 106k FLASH = GND VFB = 0.3V Conditions mV mV A V V A s o C (c) 2009 Exar Corporation 2/12 Rev. 2.0.0 S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver BLOCK DIAGRAM Fig. 2: SP6686 Block Diagram PIN ASSIGNEMENT Fig. 3: SP6686 Pin Assignement (c) 2009 Exar Corporation 3/12 Rev. 2.0.0 S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver PIN DESCRIPTION Name VIN C1 C2 Pin Number 1 2 3 Description Input voltage for the charge pump. Decouple with 2.2F ceramic capacitor close to the pins of the IC. Positive input for the external fly capacitor. Connect a ceramic 0.47F capacitor close to the pins of the IC. Negative input for the external fly capacitor. Connect a ceramic 0.47F capacitor close to the pins of the IC. 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. Shutdown control input. Connect to VIN for normal operation, connect to ground for shutdown. 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)*11.2K Feedback input for the current control loop. Connect directly to the current sense resistor. Internal ground pin. Control circuitry returns current to this pin. Power ground pin. Fly capacitor current returns through this pin. Charge Pump Output Voltage. Decouple with an external capacitor. At least 1F is recommended. Higher capacitor values reduce output ripple. FLASH 4 EN RSET FB SGND PGND VOUT 5 6 7 8 9 10 ORDERING INFORMATION Part Number SP6686ER-L Temperature Range -40CTA+85C -40CTA+85C SP6686 Evaluation Board Marking SP66 86ER WWX SP66 86ER WWX Package DFN-10 Packing Quantity Bulk Note 1 RoHS Compliant Halogen Free RoHS Compliant Halogen Free Note 2 SP6686ER-L/TR SP6686EB DFN-10 3K/Tape & Reel "WW" = Work Week - "X" = Lot Number (c) 2009 Exar Corporation 4/12 Rev. 2.0.0 S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver TYPICAL PERFORMANCE CHARACTERISTICS All data taken at VIN = 3.6V, TA = 25C, unless otherwise specified - Schematic and BOM from Application Information section of this datasheet. D1 = AOT 2015HPW-1915B LED. Fig. 4: Output Current vs Supply Voltage CIN=2.2F, CFC=0.47F,COUT=1F Fig. 5: Output Current vs Supply Voltage CIN=2.2F, CFC=0.47F,COUT=1F Fig. 6: Efficiency vs Supply Voltage CIN=2.2F, CFC=0.47F,COUT=1F Fig. 7: Efficiency vs Supply Voltage CIN=2.2F, CFC=0.47F,COUT=1F Fig. 8: Ripple 1x Flash 400mA, Ch1=VIN, Ch2=VOUT VIN=4.2V, CIN=4.7F, CFC=0.47F,COUT=2.2F Fig. 9: Ripple 2x Flash 400mA, Ch1=VIN, Ch2=VOUT VIN=3.6V, CIN=4.7F, CFC=0.47F,COUT=2.2F (c) 2009 Exar Corporation 5/12 Rev. 2.0.0 S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver Fig. 10: Ripple 1x Torch 150mA, Ch1=VIN, Ch2=VOUT VIN=4.2V, CIN=4.7F, CFC=0.47F,COUT=2.2F Fig. 11: Ripple 2x Torch 150mA, Ch1=VIN, Ch2=VOUT VIN=3.0V, CIN=4.7F, CFC=0.47F,COUT=2.2F Fig. 12: Output Current vs Supply Voltage D1=AOT2015HPW-1915 LED, RSENSE=0.3 RSET=106k, CIN=2.2F, CFC=0.47F,COUT=1F Fig. 13: Output Current vs Supply Voltage D1=AOT3228HPW0303B LED, RSENSE=0.3 RSET=140k, CIN=2.2F, CFC=0.47F,COUT=1F Fig. 14: Efficiency vs Supply Voltage D1=AOT2015HPW-1915 LED, RSENSE=0.3 RSET=106k, CIN=2.2F, CFC=0.47F,COUT=1F Fig. 15: Efficiency vs Supply Voltage D1=AOT3228HPW0303B LED, RSENSE=0.3 RSET=140k, CIN=2.2F, CFC=0.47F,COUT=1F (c) 2009 Exar Corporation 6/12 Rev. 2.0.0 S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver Fig. 16: Battery Current vs Supply Voltage D1=AOT2015HPW-1915 LED, RSENSE=0.3 RSET=106k, CIN=2.2F, CFC=0.47F,COUT=1F Fig. 17: Battery Current vs Supply Voltage D1=AOT3228HPW0303B LED, RSENSE=0.3 RSET=140k, CIN=2.2F, CFC=0.47F,COUT=1F Fig. 18: Startup Torch VIN=3.6V, VOUT=3.1V, CIN=4.7F, CFC=0.47F,COUT=2.2F Fig. 19: Startup Flash VIN=3.6V, VOUT=3.5V, CIN=4.7F, CFC=0.47F,COUT=2.2F Fig. 20: Torch in 1x to Flash in 1x Mode VIN=4.2V, CIN=4.7F, CFC=0.47F,COUT=2.2F Fig. 21: Torch in 1x to Flash in 2x Mode VIN=3.6V, CIN=4.7F, CFC=0.47F,COUT=2.2F (c) 2009 Exar Corporation 7/12 Rev. 2.0.0 S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver THEORY OF OPERATION The SP6686 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 SP6686 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 milliseconds 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 SP6686 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 200sec, and then SP6686 goes through a soft-start mode designed to reduce inrush current. The SP6686 starts in the 1x mode, which acts like a linear regulator to control the output current by continuously monitoring the feedback pin FB. In 1x mode, if the SP6686 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 SP6686 automatically switches to the 2x mode. The SP6686 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 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 SP6686, 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. In the Torch mode, (Flash = GND) the Flash pin is set to logic low and the SP6686 FB pin regulates to 50mV output: 50 (c) 2009 Exar Corporation 8/12 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: 1.26 11.2 Where 1.26V is the internal bandgap reference voltage and 11.2k is an internal resistance used to scale the RSET current. Typical values of RSET are 40k to 180k 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: OVER TEMPERATURE PROTECTION When the temperature of the SP6686 rises above 145C, the over temperature protection circuitry turns off the output switches to prevent damage to the device. If the temperature drops back down below 135C, the part automatically recovers and executes a soft start cycle. OVER VOLTAGE PROTECTION The SP6686 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 OVER CURRENT PROTECTION The over current protection circuitry monitors the average current out of the VOUT=50mV (Torch Mode) pin. If the average output current exceeds approximately 1Amp, then the over current protection circuitry shuts off the output switches to protect the chip. COMPONENT SELECTION The SP6686 charge pump circuit requires 3 capacitors: 4.7F input, 1F output and Rev. 2.0.0 S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver 0.47F fly capacitor are typically recommended. For the input capacitor, a larger value of 10F will help reduce input voltage ripple for applications sensitive to ripple on the battery voltage. All the capacitors should be ceramic to obtain low ESR, which improves bypassing on the input and output and improves output voltage drive by reducing output resistance. X5R or X7R Ceramic capacitors are recommended for most applications. A selection of recommended capacitors is included in Table 1. 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 SP6686. The fly capacitor should be located as close to the C1 and C2 pins as possible. The sense resistor RSENSE is determined by the value needed in the Torch mode for the desired output current by the equation: Next, the RSET resistor can be selected for Flash mode using the following equation: 1.26 11.2 For an example of 150mA Torch mode and 400mA Flash mode, the values RSENSE=0.33, VFB=135mV (Flash Mode), and RSET=106k are calculated. The power obtained in the Flash mode would be: 133 400 53 The typical 0603 surface mount resistor is rated at 1/10 Watt continuous power and 1/5 Watt pulsed power, more than enough for this application. For other applications, the PFLASH can be calculated from the resistor size selected. The RSENSE resistor is recommended to be size 0603 for most applications. EVALUATION BOARD LAYOUT Where VFB=50mV in 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: Where IOUT is for Flash Mode (c) 2009 Exar Corporation 9/12 Rev. 2.0.0 S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver Manufacturer Part Number Value Size/Type ESR TDK TDK TDK TDK Murata Murata Murata Murata C1005X5R0J474K C1005X5R0J105K C1608X5R0J225K C1608X5R0J475K GRM155R60J474KE19D GRM155R60J105KE19D GRM188R60J225KE19D GRM188R60J475KE19D 0.47uF/6.3V 1uF/6.3V 2.2uF/6.3V 4.7uF/6.3V 0.47uF/6.3V 1uF/6.3V 2.2uF/6.3V 4.7uF/6.3V 0402/X5R/0.55mm 0402/X5R/0.55mm 0603/X5R/0.9mm 0603/X5R/0.9mm 0402/X5R/0.55mm 0402/X5R/0.55mm 0603/X5R/0.8mm 0603/X5R/0.8mm 0.03 0.03 0.03 0.02 0.03 0.03 0.03 0.02 Table 1: Recommended Capacitors Part Reference RSET RSET RSET RSET RSET RSET RSET RSET RSET RSET RSENSE RSENSE RSENSE RSENSE RSENSE Value 68K 75K 82K 91K 100K 110K 120K 130K 140K 150K 0.22 0.27 0.33 0.39 0.47 Tolerance 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% Size 0402 0402 0402 0402 0402 0402 0402 0402 0402 0402 0603 0603 0603 0603 0603 Table 2: Resistor Value and Sizes (c) 2009 Exar Corporation 10/12 Rev. 2.0.0 S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver PACKAGE SPECIFICATION 10-PIN DFN (c) 2009 Exar Corporation 11/12 Rev. 2.0.0 S P6 6 8 6 400mA Buck/Boost Charge Pump LED Driver REVISION HISTORY Revision 2.0.0 Date 08/04/2009 Reformat of datasheet. Added EN pin ESD information. Description FOR FURTHER ASSISTANCE Email: Exar Technical Documentation: customersupport@exar.com 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. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited. or its in all (c) 2009 Exar Corporation 12/12 Rev. 2.0.0 |
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