SP6687ER1-L

® SP6687 C2P C2N C1N 12 11 10 9 13 LED2 15 LED1 16 Pin 1 Orientation 16 Pin QFN 1 2 3 4 CTRL2 14 CTRL0 LED3 SP6687 CTRL1 LED4 EN FEATURES ■ High Efficiency > 90% ■ Support up to 4 White LEDs with current matching ■ Three Charge Pump Modes: X1, X1.5, X2 ■ Soft Start Function ■ Short Circuit Protection ■ Output Overvoltage Protection ■ Thermal Shutdown ■ Programmable LED drive capability ■ PWM Dimming Control ■ 1MHz Fixed Frequency Oscillator ■ Low 1µA Shutdown Current ■ Pin Compatible with SC604 GND 4 Channel Charge Pump White LED Driver 8 C1P 7 VIN 6 VOUT 5 ISET Now Available in Lead-Free Packaging APPLICATIONS ■ Mobile phones ■ White LED Backlighting ■ Camera Flash LED lighting DESCRIPTION The SP6687 is a compact, highly efficient and highly integrated 4 channel charge pump white LED driver. It can support from 1 to 4 White LEDs and is optimized for Li-Ion battery applications. Current matching allows all 4 LEDs to maintain consistent brightness. Users can control White LEDs by three programming bits. Each channel can support up to 30mA of current. This device is available in a 4mm x 4mm, 16 pin QFN package. TYPICAL APPLICATION CIRCUIT C2 1µF C1 1µF 7 VIN 8 9 11 C1P C1N C2P ® Li-ion Battery 1 CIN EN 1µF 2 CTRL0 3 4 5 SP6687 10 C2N VOUT 6 LED1 16 CTRL1 LED2 15 CTRL2 LED3 ISET GND LED4 COUT 1µF 14 13 12 RSET Typical Application Circuit for 4-White LEDs Date: 11/15/05 SP6687 4Channel Charge Pump White LED Driver 1 © Copyright 2005 Sipex Corporation 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. Input Voltage.....................................................-0.3 to 6V Output Voltage..................................................-0.3 to 6V Power Dissipation, PD @ TA = 25ºC QFN-16L 4x4...........................................................2.5W Package Thermal Resistance QFN-16L 4x4, OJA................................................40ºC/W Junction Temperature Range...............-40ºC to 125ºC Storage Temperature ......................... -65ºC to 150°C Operating Temperature ....................... -40°C to 85°C ESD Susceptibility Human Body Model...............................................2kV Machine Model.....................................................200V ELECTRICAL CHARACTERISTICS Unless otherwise specified: VIN = 2.85V to 5.5V, C1 = C2 =1.0µF (ESR = 0.03Ω, TA = 25°C) PARAMETER MIN Input Supply Voltage 2.5 Under Voltage Lockout Threshold 1.8 Under Voltage Lockout Hysteresis Current into LEDs 1, 2, 3, and 4 TYP 2.2 MAX UNITS 5.5 V 2.4 V 50 CONDITIONS VIN Rising mV 18.5 20 21.5 mA R SET = 24.0kΩ 4.5 5 5.5 mA R SET = 91.0kΩ 2 20 mA 2.7V < VIN < 5.5V 2 30 mA 3.1V < VIN < 5.5V Quiescent Current 3 4 mA FOSC = 1MHz, IOUT = 0mA Quiescent Current in Shutdown 1 10 µA VIN = 4.5V, En Pin = ZeroV ILED Accuracy (Note 1) 2 7.5 % 2mA < ILED < 30mA Current Matching (Note 2) 1 5 % 2mA < ILED < 30mA 1x mode to 1.5x mode Transition Voltage (V IN Falling) 3.75 TBD V VLED = 3.5V, IOUT = 80mA ILED1 = I LED2 = ILED3 = ILED4 = 20mA 1.5x mode to 2x mode Transition Voltage (V IN Falling) 2.65 2.8 V VLED = 3.5V, IOUT= 80mA ILED1 = I LED2 = ILED3 = ILED4 = 20mA Oscillator Frequency 0.8 1.0 1.2 MHz Input Current Limit 250 400 650 mA 5.5 6 V Output Over Voltage Protection Date: 11/15/05 SP6687 4Channel Charge Pump White LED Driver 2 Short Circuit applied from VOUT to GND Open circuit at any LED that is programmed to be in the ON state © Copyright 2005 Sipex Corporation ELECTRICAL CHARACTERISTICS Unless otherwise specified: VIN = 2.85V to 5.5V, C1 = C2 =1.0µF (ESR = 0.03Ω, TA = 25°C) PARAMETER MIN TYP MAX UNITS CONDITIONS V Input High Logic threshold (EN, CTRL0, CTRL1, CTRL2) 0.4 V Input Low Logic threshold (EN, CTRL0, CTRL1, CTRL2) Input High Current 1 µA VIH = VIN Input Low Current 1 µA VIL= GND 180 ºC Input High Threshold 1.5 Input Low Threshold Thermal Shutdown Threshold 140 150 Thermal Shutdown Hysteresis Note 1: ILED(ERR) = 10 ºC ILED(MEA) - ILED(SET) X 100% ILED(SET) Note 2: Current Matching refers to the difference in current from one LED to the next. (ILED Current Matching ILED(MAX) - ILED(MIN) ILED(MAX) + ILED(MIN) X 100%) FUNCTIONAL DIAGRAM C1P C1N C2P C2N VIN GND 1x/1.5x/2x Charge Pump 1MHz Oscillator 1MHz Mode Decision I-Setting VOUT ISET ISET LED1 ISET EN Bandgap VREF LED2 LED3 LED4 CTRL0 CTRL1 CTRL2 Date: 11/15/05 Decoder 306mV SP6687 4Channel Charge Pump White LED Driver 3 © Copyright 2005 Sipex Corporation PIN DESCRIPTION PIN # PIN NAME DESCRIPTION 1 EN 2 CTRL0 Output Control Bit 0 (See table 1) 3 CTRL1 Output Control Bit 1 (See table 1) 4 CTRL2 Output Control Bit 2 (See table 1) 5 ISET LED current is set by the value of the resistor RSET connected from the ISET pin to ground. Do not short the ISET pin. Voltage for ISET is typically 1.1V. 6 VOUT Output Voltage Source for connection to the LED anodes. 7 VIN 8 C1P Positive Terminal of Bucket Capacitor 1 9 C1N Negative Terminal of Bucket Capacitor 1 10 C2N Negative Terminal of Bucket Capacitor 2 11 C2P Positive Terminal of Bucket Capacitor 2 12 GND Ground 13 to 16 LED1 to 4 Current Sink for LED. (If not in use, pin may be left open, grounded, or connected to VIN) Exposed Pa d GND Exposed pad should be soldered to PCB board and connected to GND Chip Enable (Active High) LED4 13 LED3 14 GND C2P C2N C1N Power Input Voltage 12 11 10 9 8 C1P 7 VIN GND VOUT LED1 16 5 ISET Pin 1 Orientation EN 1 2 3 4 CTRL2 6 CTRL1 15 CTRL0 LED2 TOP VIEW Date: 11/15/05 SP6687 4Channel Charge Pump White LED Driver 4 © Copyright 2005 Sipex Corporation THEORY OF OPERATION The SP6687 is a high efficiency charge pump white LED driver. It provides 4 channels of low drop-out voltage current source to regulate the current for 4 white LEDs. For high efficiency, the SP6687 implements 3 modes of charge pump: x1/x1.5/x2 modes. An external RSET is used to set the current level of the White LEDs. SP6687 has an input current regulation circuit to reduce the input ripple. where VISET =1.1V, and RSET is the resistance connected from ISET to GND. ILED =440x VISET (R ) SET Thermal Shutdown The SP6687 provides a high current capability to drive 4 white LEDs. A thermal shutdown circuit is needed to protect the chip from thermal damage. When the chip reaches the shutdown temperature of 150ºC, the thermal shutdown circuit turns off the chip to prevent thermal accumulation in the chip. Soft Start The SP6687 includes a soft start circuit to limit the inrush current at power on and mode switching. The soft start circuit holds the input current level long enough for output capacitor COUT to reach a desired voltage level. When the soft start turns off, the SP6687 will not sink current spiking from VIN. Mode Decision The SP6687 uses a smart mode decision method to select the working mode for maximum efficiency. The mode decision circuit senses the output and LED voltage for up/down selection. Dimming Control CTRL0, CTRL1 and CTRL2 are used to control the on/off of correlated White LEDs. When an external PWM signal is connected to the control pin, the brightness of the white LEDs is adjusted by the duty cycle. Overvoltage Protection SP6687 regulates the output voltage by controlling the input current. When the output voltage reaches the designated level, SP6687 reduces the input current. Subsequently, the output voltage regulation also serves as an overvoltage protection circuit. Short Circuit Protection A current limiting circuit is also included in the SP6687 for short circuit protection. Whenever the output sources a dangerously high current, the current limiting circuit takes over the output regulation circuit and reduces the output current to an acceptable level. LED Current Setting The current flowing through White LEDs connected to the SP6687 can be set by RSET. Every current that flows through each respective White LED is 440 times greater than the current of RSET. The white LED current can be estimated by following equation: APPLICATION INFORMATION C2 1µF C1 1µF 7 Li-ion Battery CIN 1 VIN 8 C1P 11 9 C1N C2P 10 C2N VOUT 6 ® EN 1µF 2 CTRL0 SP6687 COUT LED1 16 3 CTRL1 LED2 15 4 CTRL2 LED3 5 1µF 14 LED4 13 ISET GND RSET 12 Typical Application Circuit For 3-White LEDs Date: 11/15/05 SP6687 4Channel Charge Pump White LED Driver 5 © Copyright 2005 Sipex Corporation APPLICATION INFORMATION C2 1µF C1 1µF 8 7 VIN C1P 11 9 C1N C2P ® CIN 1µF Li-ion Battery 1 EN COUT 1µF LED1 16 CTRL1 LED2 4 CTRL2 5 6 VOUT SP6687 2 CTRL0 3 10 C2N LED3 ISET GND 15 14 LED4 13 12 RSET Typical Application Circuit for 2-White LEDs Control Inputs Output Status CTRL2 CTRL1 CTRL0 LED4 LED3 LED2 LED1 0 0 0 OFF OFF OFF ON 0 0 1 OFF OFF ON OFF 0 1 0 OFF ON OFF OFF 0 1 1 ON OFF OFF OFF 1 0 0 OFF OFF ON ON 1 0 1 OFF ON ON ON 1 1 0 ON ON ON ON 1 1 1 OFF OFF OFF OFF Table 1. Typical application circuit for PWM dimming using a DC voltage into ISET. Date: 11/15/05 SP6687 4Channel Charge Pump White LED Driver 6 © Copyright 2005 Sipex Corporation TYPICAL PERFORMANCE CHARACTERISTICS Figure 9: SP6687 Efficiency vs. Input voltage at ILED = 60mA, VF = 3.3V (falling voltage) Figure 10: SP6687 Efficiency vs. Input voltage at ILED = 60mA, VF = 3.6V (falling voltage) Figure 11: SP6687 Efficiency vs. Input voltage at ILED = 80mA, VF = 3.3V (falling voltage) Figure 12: SP6687 Efficiency vs. Input voltage at ILED = 80mA, VF = 3.6V (falling voltage) Date: 11/15/05 SP6687 4Channel Charge Pump White LED Driver 7 © Copyright 2005 Sipex Corporation APPLICATION INFORMATION Selecting Capacitors Figure 2 shows the typical value of RSET versus average LED current and Table 2 shows the values of RSET for a fixed LED current. To get better performance from the SP6687, the selection of appropriate capacitors is very important. These capacitors determine some parameters such as input and output ripple, power efficiency, maximum supply current by the charge pump and startup time. To reduce the input and output ripple effectively, low ESR ceramic capacitors are recommended. Typical Curve for RSET vs. Avg. LED Current 300 RSET Value (k_) Ω 250 To reduce output ripple, increasing the output capacitance COUT is generally necessary. However, this will increase the startup time of the output voltage. For LED driver applications, the input voltage ripple is more important than output ripple. Input ripple is controlled by the input capacitor CIN -- increasing the value of input capacitance can further reduce the ripple. Practically, the input voltage ripple depends on the impedance of the power supply. If a single input capacitor CIN cannot satisfy the requirement of the application, it is necessary to add a low-pass filter. Figure 1 shows a CR-C filter used on the SP6687. The input ripple can be reduced to less than 30mVp-p when driving 80mA of output current. 200 150 100 50 0 0 5 10 15 20 25 30 LED Current (mA) Figure 2. The typical curve of RSET vs. LEDs average current. ILED (mA) RSET (k Ω ) Nearest Standard Value for RSET (k Ω ) 5 91.0 91.0 10 47.9 47.5 15 32.7 32.4 20 24.0 24.0 25 19.6 19.6 30 16.4 16.5 ® V IN 2.2µF 1.0Ω V IN SP6687 2.2µF Figure 1. C-R-C filter used to reduce input ripple. The flying capacitors C1 and C2 determine the supply current capability of the charge pump and influence the overall efficiency of the system. Lower values will improve efficiency, but will limit the current to the LEDs at low input voltages. For 4 X 20mA load over the entire input range of 2.7 to 5.5V, a capacitor of 1µF is optimal. Table 2. RSET Value Selection If maximum accuracy is required, a precision resistor is needed. The following equation shows how to calculate the error: ILED(ERR) = ILED(MEAS) - ILED(SET) X 100% Setting the LED Current The SP6687 can be set to a fixed LED current by a resistor RSET connected from ISET to GND. RSET establishes the reference current and mirrors the current into LED1, LED2, LED3, and LED4. The current into each LED is about 440 times the current that flows through RSET. The approximate setting formula is given as follows: ILED= ILED(SET) Where ILED(MEAS) is practical measured LED current and ILED(SET) is the LED current which is determined by RSET. 484(V) RSET(Ω) Date: 11/15/05 SP6687 4Channel Charge Pump White LED Driver 8 © Copyright 2005 Sipex Corporation APPLICATION INFORMATION LED Current Setting with NMOS LED Dimming Control Methods LED current setting control can also be achieved by using an external NMOS transistor to change the equivalent resistor of the ISET pin. Figure 3 illustrates this application circuit which has 3 bit signals and can set 8 different levels of LED current. Table 3 shows the relation between the equivalent resistor of the ISET pin and the respective control signal. The SP6687 uses two methods to achieve LED dimming control. These methods are detailed below. PWM Dimming The first dimming method utilizes a PWM control signal into CTRL0, CTRL1, and CTRL2. Table 1 shows the relation between CTRLx and the 4 LED current states. For example, when CTRL1 and CTRL2 are at logic high and CTRL0 receives a PWM signal then 4 LEDs will be dimmed simultaneously. The average LED current can be derived by using a known PWM signal value. When the PWM signal logic is low the current can be set at a fixed value with the RSET resistor. The following equation will give the approximate value of the LED current: TOFF X ILED(ON) ILED(AVG) = TPWM ® SP6687 R1 ISET S1 R4 R2 S2 R3 Where TPWM is the period of the PWM dimming signal. TOFF is the time of the PWM signal at low. ILED(ON) is LED ON state current. S3 Figure 3. Typical application circuit for setting LED current using an NMOS transistor to set RSET S1 S2 S3 VIN Equivalent Resister of ISET pin (RSET) 0 0 0 RSET=R4 0 0 1 RSET=R3//R4 0 1 0 RSET=R2//R4 0 1 1 RSET=R2//R3//R4 1 0 0 RSET=R1//R4 1 0 1 RSET=R1//R3//R4 1 1 0 RSET=R1//R2//R4 1 1 1 RSET=R1//R2//R3//R4 ® SP6687 CTRL2 CTRL1 CTRL0 EN PWM LED LED ON OFF Figure 4. Typical application circuit for PWM dimming when driving 4 LEDs. VIN ® Table 3. Control signal and equivalent resistor of the ISET pin. SP6687 CTRL2 CTRL1 CTRL0 EN PWM LED LED ON OFF Figure 5. Typical application circuit for PWM dimming when driving 3 LEDs. Date: 11/15/05 SP6687 4Channel Charge Pump White LED Driver 9 © Copyright 2005 Sipex Corporation APPLICATION INFORMATION VIN ® Dimming using a DC voltage added to ISET SP6687 CTRL2 CTRL1 CTRL0 EN PWM Using an analog input voltage VADJ via a resistor RADJ that connects to the ISET pin is another method for dimming control of LEDs. Figure 7 shows the application circuit. For this application the LED current can be derived from the following equation: LED LED ON OFF ILED = 440 X [1.1 x (1/RSET + 1/RADJ) - VADJ/RADJ] Figure 6. Typical application circuit for PWM dimming when driving 2 LEDs. VADJ Due to the 100µs delay time between mode transfers, the duty cycle of the dimming frequency should not exceed the maximum duty cycle on the CTRLx pins. For best performance it is recommended to keep the dimming frequency between 200Hz and 1kHz. When the duty cycle is exceeded, the SP6687 cannot transfer modes properly. The following equation shows the relation between maximum duty of the CTRLx pins and the PWM dimming frequency: RADJ ® RSET SP6687 ISET CTRL2 CTRL1 CTRL0 EN VIN DMAX =(1-100 x10 -6 x FD) Where DMAX is the Maximum Duty of CTRLX and FD is the PWM Dimming Frequency. Dimming Frequency (Hz) CTRLX Maximum Duty ILED Minimum Duty 1K 0.90 0.10 900 0.91 0.09 800 0.92 0.08 700 0.93 0.07 600 0.94 0.06 500 0.95 0.05 400 0.96 0.04 300 0.97 0.03 200 0.98 0.02 Figure 7. Typical application circuit for PWM dimming using a DC voltage into ISET. VADJ 1.6V 0.8V 13mA ILED 0V 20mA 6.5mA 0mA Figure 8. SP6687 dimming control application using a DC voltage into ISET. Figure 8 shows the relation between VADJ and ILED of a typical application example, with VADJ from 0 to 2.5V, RSET = 43kΩ and RADJ = 55kΩ. Table 4. Dimming frequency relative to Min/Max duty. Date: 11/15/05 2.5V SP6687 4Channel Charge Pump White LED Driver 10 © Copyright 2005 Sipex Corporation PACKAGE: 16 PIN QFN D D2 K 13 14 15 16 Pin1 Designator to be within this INDEX AREA (D/2 x E/2) INDEX AREA (D/2 x E/2) 1 E2 2 E 3 4 K e b L TOP VIEW BOTTOM VIEW غ A A3 Seating Plane A1 4x4 16 Pin QFN SYMBOL b D D2 E E2 e L JEDEC MO-220 Millimeters Controlling Dimension MIN 0.80 0.00 A A1 A3 K ø SIDE VIEW 0.20 0º 0.25 2.20 2.20 0.45 NOM 0.90 0.02 0.20 REF 0.30 4.00 BSC 2.40 4.00 BSC 2.40 0.65 BSC 0.55 SIPEX Pkg Signoff Date/Rev: Date: 11/15/05 MAX 1.00 0.05 14º 0.35 2.60 2.60 0.65 Variation VGGC-4 Inches Conversion Factor: 1 Inch = 25.40 mm MIN NOM MAX 0.031 0.035 0.039 0.000 0.001 0.002 0.008 REF 0.008 0º 14º 0.010 0.012 0.014 0.157 BSC 0.087 0.094 0.102 0.157 BSC 0.087 0.094 0.102 0.026 BSC 0.018 0.022 0.026 JL Oct31-05/Rev A SP6687 4Channel Charge Pump White LED Driver 11 © Copyright 2005 Sipex Corporation ORDERING INFORMATION Part Number Operating Temperature Range Package Type SP6687ER1-L/TR ....................................... -40°C to +85°C ........................................ 16 Pin 4mmx4mm QFN Available in lead-free packaging only. -L = lead-free /TR = Tape and Reel Pack quantity is 3,000 for QFN. 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: 11/15/05 SP6687 4Channel Charge Pump White LED Driver 12 © Copyright 2005 Sipex Corporation