SP7685ER-L/TR

SP7685 1.2A Buck/Boost Charge Pump LED Driver FEATURES ■ Output Current up to 1.2A ■ Up to 94% Efficiency in Torch Mode ■ Adjustable FLASH Mode Current ■ Minimum External Components: No Inductors ■ Automatic Buck/Boost Mode Switchover ■ Wide VIN Range: 2.7V to 5.5V ■ High Frequency Operation: 2.4 MHz ■ 50mV Reference for low Loss Sensing ■ IQ < 2μA in Shutdown ■ PWM Dimming Control ■ Automatic Soft Start Limits Inrush Current ■ Overvoltage Protection on Output ■ Overcurrent/temperature Protection ■ Low Ripple and EMI ■ Ultra-low Dropout Voltage in Buck Mode ■ 2.6 Second Timeout in Flash Mode ■ Space Saving RoHS Compliant, Lead Free Package: 10-pin 3mm x 3mm DFN VIN 1 C1 2 SP7685 C2 3 10 Pin DFN FLASH EN 10 VOUT 9 PGND 8 SGND 4 7 FB 5 6 RSET APPLICATIONS ■ White LED Torch/Flash for Cell Phones, DSCs, and Camcorders ■ White LED Backlighting ■ Generic Lighting/Flash/Strobe Applications ■ General Purpose High Current Boost DESCRIPTION The SP7685 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 SP7685 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 SP7685 is offered in 10-pin DFN package. TYPICAL APPLICATION CIRCUIT VIN (3.0 - 4.2V) O CIN 10μF VIN CFC 1μF TORCH/FLASH ENABLE ¤ VOUT COUT 10μF C1 SP7685 PGND C2 SGND FLASH FB RSET EN RSET 80KΩ Date: 6/20/06 Rev T 1A Flash 200mA Torch PWF1 WLED SP7685, 1.2A Buck/BoostCharge Pump LED Driver 1 RSENSE 0.22Ω © 2006 Sipex Corporation ABSOLUTE MAXIMUM RATINGS VIN , VOUT ....................................................................... -0.3V to 6V Output Current Pulse (Flash) ................................. 2A Output Current Continuous (Torch) ..................... 0.4A Storage Temperature ...................... -65°C to +150°C Operating Temperature ..................... -40°C to +85°C VEN ............................................................ 0.0V to 7V 3x3 10 DFN .........................................OJA = 40.5°C/W 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 TA = -40°C to +85°C, VIN =3.6V, CIN = 10μF, CFC =1.0μF, COUT =10μF. VSHDN = VIN, typical values at 25°C. The ♦ denotes the specifications which apply over the full operating temperature range unless otherwise noted. PARAMETER Operating Input Voltage MIN. TYP. 2.7 Quiescent Current 0.5 MAX. UNITS CONDITIONS 5.5 V ♦ 3 mA ♦ 2 Shutdown Current FLASH = High, 2x mode 2 Oscillator Frequency V IN = 2.7 - 5.5V FLASH = GND, 1X Mode, ILOAD = 100μA μA V IN = 5.5V, VEN = 0.0V 2.4 MHz Charge Pump Equivalent Resistance (x2 mode) 4 Ω V FB = 0.0V, V IN= 3.6V Charge Pump Equivalent Resistance (x1 mode) 0.4 0.7 Ω V IN = 3.6V 45 50 55 mV ♦ FLASH = GND 138 150 162 mV ♦ FLASH = High, R SET = 53.6kΩ . 400 mV ♦ FLASH = High. Guaranteed by design. FB Pin Current 0.5 μA EN, FLASH Logic Low 0.4 V ♦ V ♦ 0.5 μA ♦ 500 μs ♦ V IN = 3.6V, FB within 90% of regulation ♦ FLASH = High FB Reference Voltage FB Reference Voltage Range EN, FLASH Logic High 100 1.3 EN, FLASH Pin Current V OUT Turn-on Time 170 Thermal Shutdown Temperature 145 Maximum Flash ON time Date: 6/20/06 Rev T 1.6 2.6 o 3.6 V FB = 0.3V C s SP7685, 1.2A Buck/BoostCharge Pump LED Driver 2 © 2006 Sipex Corporation PIN DESCRIPTION PIN PIN NAME NUMBER DESCRIPTION 1 VIN Input Voltage for the charge pump. Decouple with 4.7µF ceramic capacitor close to the pins of the IC. 2 C1 Positive input for the external flying capacitor. Connect a ceramic 1µF capacitor close to the pins of the IC. 3 C2 Negative input for the external flying capacitor. Connect a ceramic 1µF capacitor close to the pins of the IC. FLASH Logic input to toggle operation 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 (R SENSE) based on desired current in TORCH mode. This pin does not have an internal pull-up/pulldown; do not leave this pin floating. 4 5 EN 6 RSET 7 FB 8 SGND 9 PGND 10 VOUT Date: 6/20/06 Rev T Shutdown control input. Connect to VIN for normal operation, connect to ground for shutdown. This pin does not have an internal pull-up/pull-down; do not leave this pin floating. 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 = RSET*14uA/5 (Flash Mode) 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. Flying capacitor current returns through this pin. Charge Pump Output Voltage. Decouple with an external capacitor. At least 1µF is recommended. Higher capacitor values reduce output ripple SP7685, 1.2A Buck/BoostCharge Pump LED Driver 3 © 2006 Sipex Corporation FUNCTIONAL DIAGRAM CLK RSET BLOCK RSET 6 + RSET RSET REF= { } RSET 5 RSET REF BG REF + - 1.26V RESISTOR TAPS COUNTER 32 COUNT FB REF 1 MUX 2x1 50mV 0 s + - FB 7 FB COMP FB COM P SGND 8 x 14μA FLASH 4 FLASH=1, S=1, RSET REF FLASH=0, S=0, 50mV SET DOMINANT S 0 CLR ONE SHOT R EN 5 VIN 1 MODE SWITCH 0 =1X 1=2X 135C ON THERMAL FAULT OVER TEMP COMP 145C OFF 2.4MHZ CLK CHARGE PUMP SWITCHES C1 C2 VOUT CLK PGND THEORY OF OPERATION The SP7685 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 SP7685 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. acts like a linear regulator to control the output current by continuously monitoring the feedback pin FB. In 1X mode, if the SP7685 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 SP7685 automatically switches to the 2X mode. The SP7685 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 or, 4) a thermal fault occurs. The SP7685 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 200μs, and then SP7685 goes through a soft-start mode designed to reduce inrush current. The SP7685 starts in the 1X mode, which 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 SP7685, 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. Date: 6/20/06 Rev T SP7685, 1.2A Buck/BoostCharge Pump LED Driver 4 © 2006 Sipex Corporation THEORY OF OPERATION In the Torch mode, (Flash = GND) the Flash pin is set to logic low and the SP7685 FB pin regulates to 50mV output: tion circuitry turns off the output switches to prevent damage to the device. If the temperature drops back down below 135 degrees Celsius, the part automatically recovers and executes a soft start cycle. VFB = 50mV (Torch Mode) 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: OVERVOLTAGE PROTECTION The SP7685 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. VFB = RSET * 14μA / 5 (Flash Mode) Where 14μA is an internal regulated current and 5 is an internal factor used to scale the VSET voltage to the VFB voltage. Typical values of RSET are 140KΩ to 35KΩ for a range of VFB = 400mV to 100mV in Flash mode. OVERCURRENT PROTECTION The over current protection circuitry monitors the average current out of the VOUT pin. If the average output current exceeds approximately 1.6 Amps, then the overcurrent protection circuitry shuts off the output switches to protect the chip. The output current is then set in either Flash or Torch mode by the equation: IOUT = VFB / RSENSE FLASH TIMEOUT PROTECTION BRIGHTNESS CONTROL USING PWM Due to the high currents typically available in Flash mode, it is necessary to protect the white LED from damage if left on too long. The SP7685 has a timeout in Flash mode of approximately 2.6 seconds after which it will shut down operation. Operation will not begin again in Flash mode until the Enable pin or Flash pin have been set Low and then High again. Dimming control can be achieved by applying a PWM control signal to the EN 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. OVERTEMPERATURE PROTECTION When the temperature of the SP7685 rises above 145˚C, the overtemperature protec- Date: 6/20/06 Rev T SP7685, 1.2A Buck/BoostCharge Pump LED Driver 5 © 2006 Sipex Corporation APPLICATION INFORMATION VIN =3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted. SP7685 Torch Output Current 300 SP7685 700mA Flash output Current 900 250 Output Current (mA) Output Current (mA) 850 200 150 -40C 100 25C 85C 50 800 750 700 650 600 -40C 550 25C 500 85C 450 0 3.0 400 3.2 3.4 3.6 3.8 4.0 4.2 3.0 Input Voltage (V) 1000mA,Vf=3.31V PWF1 700mA,Vf=3.24V PWF1 700mA,Vf=3.92V AOT 200mA,Torch Mode 3.2 3.4 3.6 3.8 4.0 4.2 4.0 4.2 90 80 70 60 50 40 1000mA,Vf=3.31V PWF1 30 20 10 700mA,Vf=3.18V PWF1 700mA,Vf=3.92V AOT 200mA,Torch 0 3.0 3.6 SP7685 Output Efficiency 100 Efficiency (%) Output Current (mA) 3.4 Input Voltage (V) SP7685 Output Current 1100 1000 900 800 700 600 500 400 300 200 100 0 3.2 3.8 4.0 3.0 4.2 3.2 3.4 3.6 3.8 Input Voltage (V) Input Voltage (V) SP7685 VFB vs RSET 450 400 350 VFB (mV) 300 250 200 Measured Calculated 150 100 50 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 RSET (KΩ) Date: 6/20/06 Rev T SP7685, 1.2A Buck/BoostCharge Pump LED Driver 6 © 2006 Sipex Corporation APPLICATION INFORMATION VIN =3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted. EN EN VOUT VOUT VFB VFB IOUT 1A/div IOUT 1A/div Torch in 1X to Flash in 1X Mode, V IN=4.2V Torch in 1X to Flash in 2X Mode, V IN=3.6V EN EN VOUT VOU VFB VFB IIN 1A/div IIN 1A/div Start Up 1000mA Flash VIN=3.6V, VOUT=3.8V Start Up 200mA Torch VIN=3.6V, VOUT=3.1V EN EN VOU VOUT VFB IIN 1A/div VFB Start Up 700mA Flash V IN=3.6V, VOUT=3.6V Date: 6/20/06 Rev T Flash Mode TimeOut Circuit at 2.6sec. VIN=4.2V, IOUT=1A SP7685, 1.2A Buck/BoostCharge Pump LED Driver 7 © 2006 Sipex Corporation APPLICATION INFORMATION VIN =3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted. Input Ripple Input Ripple Output Ripple Output Ripple Ripple 1X Torch 200mA, V IN=4.2V Ripple 2X Torch 200mA, V IN=3.0V Input Ripple Input Ripple Output Ripple Output Ripple Ripple 1X Flash 700mA, V IN=4.2V Ripple 2X Flash 700mA, V IN=3.6V Input Ripple Input Ripple Output Ripple Output Ripple Ripple 1X Flash 1000mA, V IN=4.2V Date: 6/20/06 Rev T Ripple 2X Flash 1000mA, V IN=3.6V SP7685, 1.2A Buck/BoostCharge Pump LED Driver 8 © 2006 Sipex Corporation COMPONENT SELECTION RESISTOR SELECTION The sense resistor RSENSE is determined by the value needed in the Torch mode for the desired output current by the equation: The SP7685 charge pump circuit requires three capacitors: 10μF input, 10μF output and 1μF fly capacitor are typically recommended. For the input capacitor, a 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 SP7685 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. 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. Part Number Capacitance/ Voltage CapacitorSize/ Type/Thickness ESR @100kHz C1005X5R0J105M C1608X5R0J475K C2012X5R0J106M GRM155R60J105KE19B GRM188R60J475KE19 GRM21BR60J106KE19L 1uF/6.3V 4.7uF/6.3V 10uF/6.3V 1uF/6.3V 4.7uF/6.3V 10uF/6.3V 0402/X5R/0.5mm 0603/X5R/0.9mm 0805/X5R/1.35mm 0402/X5R/0.55mm 0603/X5R/0.9mm 0805/X5R/1.35mm 0.03 0.02 0.02 0.03 0.02 0.02 Manufacturer's Website TDK: www.tdk.com TDK: www.tdk.com TDK: www.tdk.com Murata: www.murata.com Murata: www.murata.com Murata: www.murata.com RSENSE = VFB/ IOUT where VFB = 50mV (Torch Mode) Table 1: Recommended Capacitors Next, the RSET resistor can be selected for Flash mode using the following equation: 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 SP7685. The fly capacitor should be located as close to the C1 and C2 pins as possible. See typical circuit layout at the end of this section for details on the recommended layout. RSET = Ω (Flash Mode) For an example of 200mA Torch mode and 700mA Flash mode, the values RSENSE = 0.22Ω, VFB = 155mV (Flash Mode), and RSET =56KΩ are calculated. The power obtained in the Flash mode would be: To obtain low output ripple, a value of 10μF is recommended for COUT. For output currents of 500mA to 1.2A, 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 4.7μF COUT is still needed. Date: 6/20/06 Rev T VFB (14uA )* 5 PFLASH = VFB *IOUT = 155mV*700mA = 109mW. The typical 0603 surface mount resistor is rated 1/10 Watt continuous power and 1/5 SP7685, 1.2A Buck/BoostCharge Pump LED Driver 9 © 2006 Sipex Corporation COMPONENT SELECTION mended to be size 0603 for most applications. The range of typical resistor values and sizes are shown here in Table 2. 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 recomPart Reference RSET RSET RSET RSET RSET RSET RSET RSET RSET RSET RSET RSET RSENSE RSENSE RSENSE RSENSE RSENSE RSENSE RSENSE Value 33kΩ 39kΩ 43kΩ 47kΩ 56kΩ 62kΩ 68kΩ 82kΩ 100kΩ 110kΩ 120kΩ 150kΩ 0.22Ω 0.27Ω 0.33Ω 0.39Ω 0.47Ω 0.56Ω 0.68Ω Tolerance 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 105% 205% Size 0402 0402 0402 0402 0402 0402 0402 0402 0402 0402 0402 0402 0603 0603 0603 0603 0603 0604 0605 Manufacturers any any any any any any any any any any any any Panasonic or Vishay Panasonic or Vishay Panasonic or Vishay Panasonic or Vishay Panasonic or Vishay Panasonic or Vishay Panasonic or Vishay Table 2: Resistor values and sizes EVALUATION BOARD CIRCUIT LAYOUT Date: 6/20/06 Rev T SP7685, 1.2A Buck/BoostCharge Pump LED Driver 10 © 2006 Sipex Corporation PACKAGE: 10 PIN DFN D D/2 ø E/2 A (A3) E 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: 6/20/06 Rev T 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 SP7685, 1.2A Buck/BoostCharge Pump LED Driver 11 © 2006 Sipex Corporation ORDERING INFORMATION Part Number Operating Temperature Range Package Type SP7685ER-L ............................................... -40°C to +85°C ....................................... (Lead Free) 10 Pin DFN SP7685ER-L/TR ........................................ -40°C to +85°C ....................................... (Lead Free) 10 Pin DFN /TR = Tape and Reel Pack quantity is 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: 6/20/06 Rev T SP7685, 1.2A Buck/BoostCharge Pump LED Driver 12 © 2006 Sipex Corporation