BCT3140EGG-TR

BCT3140 1000mA Buck/Boost Charge Pump LED Driver BCT3140 1000mA Buck/Boost Charge Pump LED Driver GENERAL DESCRIPTION FEATURES The BCT3140 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 BCT3140 automatically switches modes between step-up and step-down ensuring that LED current does not depend on the forward voltage. It switches at 1.5MHz, allowing the use of tiny components. The supply voltage ranges from 2.7V to 5.5V and is ideally suited for all applications powered by a single LI-Ion battery cell or three to four NiCd, NiMH, or Alkaline battery cells. The BCT3140 also features a very low shutdown current, an automatic soft-start mode to limit inrush current, as well as over current, over voltage and over thermal shutdown control. A low current sense reference voltage (47mV) allows the use of small 0603 current sensing resistors. Output Current up to 1000mA Up to 90% Efficiency in Torch Mode Adjustable FLASH Mode Current 1x and 2x Automatic Modes for High Efficiency Input Voltage Range: 2.7V to 5.5V Minimum External Components: No Inductors High Frequency Operation: 1.5MHz Low 47mV Reference For Low Loss Sensing Built-In Soft Start Limits Inrush Current Low Input and Output Ripple and Low EMI Output Over Voltage Protection Over-current and Over-temperature Protection Available in Green DFN3x3-10L Package APPLICATIONS White LED Torch, Flash for Cell Phones, DSCs and Camcorders White LED Backlighting Generic Lighting, Flash and Strobe Applications General Purpose High Current Boost The BCT3140 is available in Green DFN3x3-10L package and is specified over an ambient temperature range of -40°C to +85°C. ORDERING INFORMATION Order Number Package Type Temperature Range Marking QTY/Reel BCT3140EGG-TR DFN-10 -40°C to +85°C 3140 3000 REV1.4 www.broadchip.com Copyright © BROADCHIP TECHNOLOGY CO., LTD 1 BCT3140 1000mA Buck/Boost Charge Pump LED Driver TYPICAL OPERATING CIRCUIT BCT3140 ABSOLUTE MAXIMUM RATINGS CAUTION VIN, VOUT........................................................-0.3V to 6V This integrated circuit can be damaged by ESD if you don’t VEN……………...............................................0V to 5.5V pay attention to ESD protection. Broadchip recommends Output Current Pulse (Flash)......................................1A that all integrated circuits be handled with appropriate Output Current Continuous (Torch)..........................0.4A precautions. Failure to observe proper handling and Package Thermal Resistance installation procedures can cause damage. ESD damage DFN3x3-10L,θJA....................................................57℃/W can range from subtle performance degradation to Storage Temperature Range.................-40℃ to +150℃ complete device failure. Precision integrated circuits may Junction Temperature..............................................150℃ be more susceptible to damage because very small Operating Temperature Range.................-40℃ to +85℃ parametric changes could cause the device not to meet its Lead Temperature (Soldering, 10 sec).....................260℃ published specifications. ESD Susceptibility HBM.....................................................................2000V Broadchip reserves the right to make any change in circuit MM.........................................................................200V design, specification or other related things if necessary without notice at any time. Please contact Broadchip sales office to get the latest datasheet. NOTE: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. REV1.4 www.broadchip.com Copyright © BROADCHIP TECHNOLOGY CO., LTD 2 BCT3140 1000mA Buck/Boost Charge Pump LED Driver PIN CONFIGURATION DFN3x3-10L TOP VIEW VIN 1 10 VOUT C1 2 9 PGND C2 3 8 SGND FLASH 4 7 FB EN 5 6 RSET GND PIN DESCRIPTION PIN NAME FUNCTION 1 VIN Input voltage for the charge pump. Decouple with 4.7μF or 10μF 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. 4 FLASH Logic input to toggle operation between FLASH and TORCH mode. In TORCH mode FB is regulated to the internal 47mV 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 and FLASH mode. 5 EN 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) X 10.2 KΩ 6 RSET 7 FB 8 SGND Internal ground pin. Control circuitry returns current to this pin. 9 PGND Power ground pin. Flying capacitor current returns through this pin. 10 VOUT Charge Pump Output Voltage. Decouple with an external capacitor. At least 1μF is recommended. If Higher value capacitor is used, output ripple is smaller. Exposed Pad GND Exposed pad should be soldered to PCB board and connected to GND. Feedback input for the current control loop. Connect directly to the current sense resistor. REV1.4 www.broadchip.com Copyright © BROADCHIP TECHNOLOGY CO., LTD 3 BCT3140 1000mA Buck/Boost Charge Pump LED Driver ELECTRICAL CHARACTERISTICS (VIN= 3.6V, CIN=4.7uF, COUT=CF=1uF, VSHDN=VIN, TA = 25℃, unless otherwise specified.) PARAMETER SYM CONDITIONS MIN TYP Input Voltage Range VIN Quiescent Current IQ MAX UNITS 2.7 VIN=2.7V to 5.5V, FLASH=0V, ILOAD=100uA 5.5 0.3 V mA FLASH=VIN, 2x Mode 2 VEN=0V, VIN=5.5V 1 uA 1.5 MHz Charge Pump Equivalent Resistance (2x mode) 5 Ω Charge Pump Equivalent Resistance (1x mode) 0.6 Ω Shutdown Current ISHDN Oscillator Frequency FB Reference Voltage VFB FB Pin Current IFB FLASH=VIN, RSET=56KΩ 229 FLASH=GND 47 mV VFB=0.3V EN, FLASH Logic Low EN, FLASH Logic High uA 0.4 V 1.2 V EN, FLASH Pin Current 1 VIN=3.6V, FB within 90% regulation VOUT Turn-on Time Thermal Shutdown Temperature Copyright © BROADCHIP TECHNOLOGY CO., LTD uA 250 us 145 ℃ REV1.4 www.broadchip.com 1 4 BCT3140 1000mA Buck/Boost Charge Pump LED Driver TYPICAL PERFORMANCE CHARACTERISTICS Ripple 1X Flash 1000mA Ripple 1X Torch 200mA Ripple 2X Flash 1000mA Ripple 2X Torch 200mA Start up 1000mA Flash Start up 200mA Torch REV1.4 www.broadchip.com Copyright © BROADCHIP TECHNOLOGY CO., LTD 5 BCT3140 1000mA Buck/Boost Charge Pump LED Driver Torch in 1X to Flash in 1X Mode Output Current Vs. Input Voltage Efficiency Vs. Input Voltage Battery Current Vs. Input Voltage REV1.4 www.broadchip.com Copyright © BROADCHIP TECHNOLOGY CO., LTD 6 BCT3140 1000mA Buck/Boost Charge Pump LED Driver TYPICAL APPLICATION The BCT3140 can be used with multiple LEDs in parallel as shown in figure 1. 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. BCT3140 Figure 1. Multiple LEDs Flash Circuit REV1.4 www.broadchip.com Copyright © BROADCHIP TECHNOLOGY CO., LTD 7 BCT3140 1000mA Buck/Boost Charge Pump LED Driver FUNCTIONAL DESCRIPTION The BCT3140 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 BCT3140 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 BCT3140 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 50μs, and then BCT3140 goes through a soft-start mode designed to reduce inrush current. The BCT3140 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 BCT3140 auto detects a dropout condition, which is when the FB pin is below the regulation point for more than 15μs, the BCT3140 automatically switches to the 2x mode. The BCT3140 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 VIN is at least 1V above VOUT. 4) A thermal fault occurs. regulated by the voltage at the FB pin. where: In the Torch mode, (Flash = “GND”) the Flash pin is set to logic low and the BCT3140 FB pin regulates to 47mV output: VFB = 47mV (Torch Mode) When in Flash mode, (Flash = “High”), the FB regulation voltage is set by the resistor RSET connected between the RSET pin and SGND and the equation: VFB = (1.26V/ RSET) × 10.2KΩ (Flash Mode) Where 1.26V is the internal bandgap reference voltage and 10.2KΩ is an internal resistance used to scale the RSET current. Typical values of RSET are 42KΩ to 170KΩ 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 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 BCT3140, which is internally limited to about 5.5V. In the 2x mode, as in the 1x mode, the output current is REV1.4 www.broadchip.com Copyright © BROADCHIP TECHNOLOGY CO., LTD 8 BCT3140 1000mA Buck/Boost Charge Pump LED Driver APPLICATIONS INFORMATION Overtemperature Protection When the temperature of BCT3140 rises above 145℃, the over temperature protection circuitry turns off the output switches to prevent damage to the device. If the temperature drops back down below 130 ℃ , the part automatically recovers and executes a soft start cycle. Overvoltage Protection The BCT3140 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 5.2V, the device resumes normal operation. capacitors with X5R or X7R temperature grade are recommended for most applications. 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 BCT3140. The flying capacitor should be located as close to the C1 and C2 pins as possible. 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. For output currents of 500mA to 700mA, the recommended CF flying capacitor value of 1μF should be used. Output currents in Flash of 100mA to 400mA can use a 0.47μF CF but a minimum 1μF COUT is still needed. Resister Selection Overcurrent Protection The over current protection circuitry monitors the average current out of the VOUT = 47mV (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 BCT3140 charge pump circuit requires 3 capacitors: 4.7μF input, 1μF output and 1μF flying capacitors 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 1.5MHz switching frequency of the BCT3140 and to obtain low ESR, which improves bypassing on the input and output and improves output voltage drive by reducing output resistance. Ceramic 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 = 47mV (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) × 10.2KΩ (Flash Mode) For an example of 190mA Torch mode and 600mA Flash mode, the values RSENSE = 0.25Ω, VFB = 150mV (Flash Mode), and RSET = 86.6KΩ are calculated. The power obtained in the Flash mode would be: PFLASH = VFB × IOUT = 150mV × 600mA = 90mW. The typical 0603 surface mount resistor is rated 1/10 Watt continuous power and 1/5 Watt pulsed REV1.4 www.broadchip.com Copyright © BROADCHIP TECHNOLOGY CO., LTD 9 BCT3140 1000mA Buck/Boost Charge Pump LED Driver 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 range of typical resistor values and sizes are shown here in Table 1. Table1. Resistor values and sizes PART REFERENCE VALUE TOLERANCE SIZE MANUFACTURERS RSET 68KΩ 5% 0402 ANY RSET 75KΩ 5% 0402 ANY RSET 82KΩ 5% 0402 ANY RSET 91KΩ 5% 0402 ANY RSET 100KΩ 5% 0402 ANY RSET 110KΩ 5% 0402 ANY RSET 120KΩ 5% 0402 ANY RSET 130KΩ 5% 0402 ANY RSET 140KΩ 5% 0402 ANY RSET 150KΩ 5% 0402 ANY RSENSE 0.22Ω 5% 0603 Panasonic or Vishay RSENSE 0.27Ω 5% 0603 Panasonic or Vishay RSENSE 0.22Ω 5% 0603 Panasonic or Vishay RSENSE 0.33Ω 5% 0603 Panasonic or Vishay RSENSE 0.39Ω 5% 0603 Panasonic or Vishay RSENSE 0.47Ω 5% 0603 Panasonic or Vishay REV1.4 www.broadchip.com Copyright © BROADCHIP TECHNOLOGY CO., LTD 10 BCT3140 1000mA Buck/Boost Charge Pump LED Driver PACKAGE OUTLINE DIMENSIONS DFN3x3-10L TOP VIEW BOTTOM VIEW SIDE VIEW REV1.4 www.broadchip.com Copyright © BROADCHIP TECHNOLOGY CO., LTD 11