Solved by SP6691 TM Micro Power Boost Regulator Series White LED Driver FEATURES ■ Drives up to 6 LEDs @ 25mA ■ Drives up to 8 LEDs @ 20mA ■ High Output Voltage: Up to 30V ■ Optimized for Single Supply, 2.7V - 4.2V Applications ■ Operates Down to 1V ■ High Efficiency: Greater Than 75% ■ Low Quiescent Current: 20µA ■ Ultra Low Shutdown Current: 10nA ■ Single Battery Cell Operation ■ Programmable Output Voltage ■ 11 switch (350mV at 350mA) ■ Lead Free, RoHS Compliant Packages: NC 1 FB 2 NC 3 SW 4 8 NC SP6691 7 SHDN 8 Pin DFN 6 VIN 5 GND APPLICATIONS ■ White LED Driver ■ High Voltage Bias ■ Digital Cameras ■ Cell Phone ■ Battery Backup ■ Handheld Computers 8 Pin DFN, 5 Pin TSOT or 5 Pin SOT23 DESCRIPTION The SP6691 is a micro power boost regulator that is specifically designed for powering series configuration white LED. The part utilizes fixed off time architecture and consumes only 10nA quiescent current in shutdown. Low voltage operation, down to 1V, fully utilizes maximal battery life. The SP6691 is offered in a 8 Pin DFN, 5-pin SOT-23 or 5 Pin TSOT package and enables the construction of a complete regulator occupying < 0.2 in2 board space. TYPICAL APPLICATION CIRCUIT 10µH L1 2.7 to 4.2V D1 SW VIN ® C2 SP6691 SHDN 4.7µF Jun26-07 Rev D C1 2.2 µF FB GND Rb Micro Power Boost Regulator Series White LED Driver © 2007 Sipex Corporation ABSOLUTE MAXIMUM RATINGS VIN ....................................................................... 15V SW Voltage .............................................. -0.4 to 30V FB Voltage ......................................................... 2.5V All other pins ................................... -0.3 to VIN + 0.3V Current into FB ................................................. ±1mA TJ Max ............................................................. 125°C Operating Temperature Range ............ -40°C to 85°C Peak Output Current < 10us SW .................... 500mA Storage Temperature ...................... -65°C to +150°C Power Dissipation. ......................................... 200mW 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 Specifications are at TA = 25°C, VIN = 3.3, VSHDN = VIN, z denotes the specifications which apply over the full operating temperature range, unless otherwise specified. PARAMETER SYMBOL MIN Input Voltage VIN 1.0 Supply Current IQ Reference Voltage VFB FB Hysteresis 1.17 TYP MAX UNITS 13.5 V 20 30 µA 0.01 1 µA 1.22 1.27 V HYST 8 IFB 15 80 nA 0.3 %/V VFB Input Bias Current 6Vo/6VI 0.1 Switch Off Time TOFF 250 VCESAT 170 450 mV 450 575 mA 5 12 µA Switch Current Limit ILIM SHDN Bias Current ISHDN SHDN High Threshold (on) VIH SHDN Low Threshold (off) VIL Switch Leakage Current 325 z z z No Switching z VFB = 1.22V SHDN = 0V (off) 1.2 ) VIN ) 13.5V nS 0.9 ISWLK CONDITIONS mV Line Regulation Switch Saturation Voltage z z z z ISW = 325mA z Switch Off, VSW = 5V VSHDN = 3.3V V 0.01 0.25 V 5 µA PIN DESCRIPTION PIN NUMBER PIN NAME 1 NC No connect. 2 FB Feedback. 3 NC No connect. 3 SW Switch input to the internal power switch 5 GND Ground 6 VIN 7 SHDN 8 NC Jun26-07 Rev D 8 PIN DFN DESCRIPTION Input Voltage. Bypass this pin with a capacitor as close to the device as possible. Shutdown. Pull high (on) to enable. Pull low (off) for shutdown. No connect. Micro Power Boost Regulator Series White LED Driver © 2007 Sipex Corporation PIN DESCRIPTION PIN NUMBER PIN NAME DESCRIPTION 1 SW Switch input to the internal power switch. 2 GND Ground 3 FB 4 SHDN 5 VIN Feedback Shutdown. Pull high (on) to enable. Pull low (off) for shutdown. Input Voltage. Bypass this pin with a capacitor as close to the device as possible. FUNCTIONAL DIAGRAM R1 1 R2 Q1 FB SW VIN 5 Q2 + - X1 DISABLE POWER TRANSISTOR SET 250ns ONE-SHOT 3 CLEAR R3 X2 DRIVER + - R4 GND SHDN 4 Shutdown Logic 2 THEORY OF OPERATION 450mA, comparator X2 clears the latch, which turns off the driver transistor for a preset 250nS. At the instant of shutoff, inductor current is diverted to the output through diode D1. During this 250nS time limit, inductor current decreases while its energy charges C2. Operation can be best understood by referring to the functional diagram above and the typical application circuit in the front page. Q1 and Q2 along with R3 and R4 form a band gap reference. The input to this circuit completes a feedback path from the high voltage output through a voltage divider, and is used as the regulation control input. When the voltage at the FB pin is slightly above 1.22V, comparator X1 disables most of the internal circuitry. Current is then provided by capacitor C2, which slowly discharges until the voltage at the FB pin drops below the lower hysteresis point of X1, about 6mV. X1 then enables the internal circuitry, turns on chip power, and the current in the inductor begins to ramp up. When the current through the driver transistor reaches about Jun26-07 Rev D At the end of the 250ns time period, driver transistor is again allowed to turn on which ramps the current back up to the 450mA level. Comparator X2 clears the latch, it’s output turns off the driver transistor, and this allows delivery of L1’s stored kinetic energy to C2. This switching action continues until the output capacitor voltage is charged to the point where FB is at band gap (1.22V). When this condition is reached, X1 turns off the internal circuitry and the cycle repeats. Micro Power Boost Regulator Series White LED Driver © 2007 Sipex Corporation PERFORMANCE CHARACTERISTICS Refer to the typical application circuit, TAMB = 25°C, unless otherwise specified. Vout = 12V Efficiency Vin = 5.0V Vin = 4.2V Vin = 3 3V 80 70 Vout = 12V Load Regulation 13.0 Vin = 5.0V Vin = 4.2V Vin = 3 3V 12.5 Vout (V) Efficiency (%) 90 60 12.0 11.5 50 0 20 40 60 80 100 120 140 11.0 160 0 20 40 60 Iout (mA) Figure 1. 12V Output Efficiency 80 140 160 70 Vin = 5.0V Vin = 4.2V Vin = 3.3V 15.5 Vout (V) Efficiency (%) 120 Vout = 15V Load Regulation 16.0 Vin = 5.0V Vin = 4.2V Vin = 3.3V Vi 60 Vin = 2.7V 15.0 14.5 50 0 20 40 60 80 100 14.0 120 0 20 Iout (mA) 60 80 100 120 Figure 4. 15V Output Load Regulation Vout = 18V Efficiency 90 40 Iout (mA) Figure 3. 15V Output Efficiency 80 70 Vout = 18V Load Regulation 19.0 Vin = 5.0V Vin = 4.2V Vin = 3 3V Vin = 5.0V Vin = 4.2V Vin = 3 3V 18.5 Vout (V) Efficiency (%) 100 Figure 2. 12V Output Load Regulation Vout = 15V Efficiency 90 80 Iout (mA) 60 18.0 17.5 50 17.0 0 20 40 60 Iout (mA) 80 100 0 Figure 5. 18V Output Efficiency Jun26-07 Rev D 20 40 60 Iout (mA) 80 100 Figure 6. 18V Output Load Regulation Micro Power Boost Regulator Series White LED Driver © 2007 Sipex Corporation PERFORMANCE CHARACTERISTICS Refer to the typical application circuit, TAMB = 25°C, unless otherwise specified. Vout = 21V Efficiency 80 Vin = 5.0V Vin = 4.2V Vin = 3 3V 21.5 70 60 21.0 20.5 50 20.0 0 10 20 30 40 Iout (mA) 50 60 70 0 Figure 7. 21V Output Efficiency 10 20 30 40 Iout (mA) Vin = 5.0V Vin = 4.2V Vin = 3 3V 60 70 70 Vin = 5.0V Vin = 4.2V Vin = 3 3V 24.5 Vout (V) 80 Vout = 24V Load Regulation 25.0 60 24.0 23.5 50 0 10 20 30 40 50 23.0 60 0 10 20 Iout (mA) 40 50 60 Figure 10. 24V Output Load Regulation Vout = 30V Efficiency 90 30 Iout (mA) Figure 9. 24V Output Efficiency Vin = 5.0V Vin = 4.2V Vin = 3 3V 30.5 Vout (V) 70 Vout = 30V Load Regulation 31.0 Vin = 5.0V Vin = 4.2V Vin = 3 3V 80 Efficiency (%) 50 Figure 8. 21V Output Load Regulation Vout = 24V Efficiency 90 Efficiency (%) Vout = 21V Load Regulation 22.0 Vin = 5.0V Vin = 4.2V Vin = 3 3V Vout (V) Efficiency (%) 90 60 30.0 29.5 50 29.0 40 0 5 10 15 20 25 0 30 5 Figure 11. 30V Output Efficiency Jun26-07 Rev D 10 15 20 25 30 Iout (mA) Iout (mA) Figure 12. 30V Output Load Regulation Micro Power Boost Regulator Series White LED Driver © 2007 Sipex Corporation PERFORMANCE CHARACTERISTICS Refer to the typical application circuit, TAMB = 25°C, unless otherwise specified. 10 Shutdown Pin Current (uA) Quiescent Current (uA) 25 20 15 Tamb=-25C Tamb=25C Tamb=85C 10 5 8 6 4 2 0 0 1.2 1.8 2.4 3 3.6 4.2 4.8 1.2 5.4 1.8 2.4 3 Input Voltage (V) Figure 13. Quiescent Current IQ vs. VIN 4.8 5.4 Switch Saturation Voltage (mV) 400 500 Current Limit (mA) 4.2 Figure 14. Shutdown Pin Current vs. VIN 600 400 300 200 100 350 300 250 200 150 100 50 0 -30 0 1.2 1.8 2.4 3 3.6 4.2 4.8 5.4 -10 Figure 15. IPK Current Limit vs. VIN 30 50 70 90 Figure 16. Switch Saturation Voltage VCESAT vs. Temperature (ISW = 450mA) 1.25 20 1.24 16 Iout/Idc (%) 1.23 1.22 1.21 1.20 -30 10 Temperature (C) Input Voltage (V) Feedback Voltage (V) 3.6 Input Voltage (V) 12 8 4 -10 10 30 50 70 0 90 0 Temperature (C) 20 40 60 80 100 PWM Duty Cycle (%) Figure 18. Average IO vs. SHDN Duty Cycle (VIN=3.3V, Standard 4x20mA WLED Evaluation Board, PWM Frequency 100Hz Figure 17. Feedback Voltage vs. Temperature Jun26-07 Rev D Micro Power Boost Regulator Series White LED Driver © 2007 Sipex Corporation PERFORMANCE CHARACTERISTICS Refer to the typical application circuit, TAMB = 25°C, unless otherwise specified. VSW EN VOUT VOUT (AC) IIN (0.5A/Div) IL (0.5A/Div) Figure 19. Startup Waveform (VIN=3.3V, VOUT=15V, IOUT=20mA) Figure 20. Typical Switching Waveforms (VIN=3V, VOUT=15V, IOUT=20mA) IOUT (100mA/Div) VOUT (AC) IL (0.5A/Div) Figure 21. Load Step Transient (VIN=3V, VOUT=21V, 1¾15mA Load Step Jun26-07 Rev D Micro Power Boost Regulator Series White LED Driver © 2007 Sipex Corporation APPLICATION INFORMATION Inductor Selection Capacitor Selection For SP6691, the internal switch will be turned off only after the inductor current reaches the typical dc current limit (ILIM=450mA). However, there is typically propagation delay of 200nS between the time when the current limit is reached and when the switch is actually turned off. During this 200nS delay, the peak inductor current will increase, exceeding the current limit by a small amount. The peak inductor current can be estimated by: Ceramic capacitors are recommended for their inherently low ESR, which will help produce low peak to peak output ripple, and reduce high frequency spikes. IPK = ILIM + VIN(MAX) L For the typical application, 4.7µF input capacitor and 2.2µF output capacitor are sufficient. The input and output ripple could be further reduced by increasing the value of the input and output capacitors. Place all the capacitors as close to the SP6691 as possible for layout. For use as a voltage source, to reduce the output ripple, a small feedforward (47pF) across the top feedback resistor can be used to provide sufficient overdrive for the error comparator, thus reduce the output ripple. • 200nS The larger the input voltage and the lower the inductor value, the greater the peak current. In selecting an inductor, the saturation current specified for the inductor needs to be greater than the SP6691 peak current to avoid saturating the inductor, which would result in a loss in efficiency and could damage the inductor. Refer to Table 2 for some suggested low ESR capacitors. Table 2. Suggested Low ESR Capacitor Choosing an inductor with low DCR decreases power losses and increase efficiency. MANUF. PART NUMBER Refer to Table 1 for some suggested low ESR inductors. MURATA 770-436-1300 GRM32RR71E 225KC01B 2.2µF /25V 1210 /X5R MURATA 770-436-1300 GRM31CR61A 475KA01B 4.7µF /10V 1206 /X5R TDK 847-803-6100 C3225X7R1E 225M 2.2µF /25V 1210 /X7R TDK 847-803-6100 C3216X5R1A 475K 4.7µF /10V 1206 /X5R Table 1. Suggested Low ESR inductor MANUF. PART NUMBER DCR (1) Current Rating (mA) MURATA 770-436-1300 LQH32CN100K11 (10µH) 0.3 450 TDK 847-803-6100 NLC453232T-100K (10µH) 0.55 500 LED Current Program In the white LEDs application, the SP6691 is generally programmed as a current source. The bias resistor Rb, as shown in the typical application circuit is used to set the operating current of the white LED using the equation: Diode Selection A schottky diode with a low forward drop and fast switching speed is ideally used here to achieve high efficiency. In selecting a Schottky diode, the current rating of the schottky diode should be larger than the peak inductor current. Moreover, the reverse breakdown voltage of the schottky diode should be larger than the output voltage. Jun26-07 Rev D CAP SIZE /VOLTAGE /TYPE Rb = VFB IF where VFB is the feedback pin voltage (1.22V), I F is the operating current of the White LEDs. In order to achieve accurate LED current, 1% Micro Power Boost Regulator Series White LED Driver © 2007 Sipex Corporation APPLICATION INFORMATION: Continued precision resistors are recommended. Table 3 below shows the Rb selection for different white LED currents. For example, to set the operating current to be 20mA, Rb is selected as 60.4 1, as shown in the schematic. Table 4. Divider Resistor Selection Table 3. Bias Resistor Selection VOUT (V) R1 (1) R2 (1) 12 1M 113K 15 1M 88.7K 18 1M 73.2K 21 1M 61.9K 30 1M 42.2K IF (mA) Rb (1) 5 243 10 121 Brightness Control 12 102 15 80.6 20 60.4 Dimming control can be achieved by applying a PWM control signal to the SHDN pin. The brightness of the white LEDs is controlled by increasing and decreasing the duty cycle of the PWM signal. A 0% duty cycle corresponds to zero LED current and a 100% duty cycle corresponds to full load current. 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. The magnitude of the PWM signal should be higher than the minimum SHDN voltage high. Output Voltage Program The SP6691 can be programmed as either a voltage source or a current source. To program the SP6691 as voltage source, the SP6691 requires 2 feedback resistors R1 & R2 to control the output voltage. As shown in Figure 22. VIN D1 L1 VOUT Open Circuit Protection C2 C1 5 VI N 4 U1 FB G ND When any white LED inside the white LED module fails or the LED module is disconnected from the circuit, the output and the feedback control will be open, thus resulting in a high output voltage, which may cause the SW pin voltage to exceed it maximum rating. In this case, a zener diode can be used at the output to limit the voltage on the SW pin and protect the part. The zener voltage should be larger than the maximum forward voltage of the White LED module. 1 SW SP6691 SHDN R1 3 1.22V R2 2 Figure 22. Using SP6691 as Voltage Source The formula and table for the resistor selection are shown below: R1 =( VOUT 1.22 Jun26-07 Rev D - 1 ) • R2 Micro Power Boost Regulator Series White LED Driver © 2007 Sipex Corporation APPLICATION INFORMATION Layout Consideration Both the input capacitor and the output capacitor should be placed as close as possible to the IC. VIN DS R1 150Kohm C2 2.2uF C1 4.7uF U1 5 V IN 4 1 SW SP6691 SHDN FB WLED MODULE D1 3 0.7V 1.22V GND DIODE Rb 34.8ohm 2 Figure 23. Improve Efficiency with Diode in Feedback Loop To further improve the efficiency and reduce the effects of the ambient temperature on the diode D1 used in method 1, an op amp circuit can be used as shown in Figure 24. The gain of the op amp circuit can be calculated by: Power Efficiency For the typical application circuit, the output efficiency of the circuit is expressed by Av = VOUT • IOUT R1 + R 2 R1 VIN • IIN If the voltage across the bias resistor is set to be 0.1V the current through R1 and R2 to be around 100µA, R1 and R2 can be selected as 1K and 11.2K respectively. LMV341 can be used because of its small supply current, offset voltage and minimum supply voltage. By using this method, the efficiency can be increased around 7%. Where VIN , IIN, VOUT, IOUT are the input and output voltage and current respectively. While the white LED efficiency is expressed by d= Murata LQH32CN100K11 L1 10uH 0.45A MBR0530 This can reduce the copper trace resistance which directly effects the input and output ripples. The feedback resistor network should be kept close to the FB pin to minimize copper trace connections that can inject noise into the system. The ground connection for the feedback resistor network should connect directly to the GND pin or to an analog ground plane that is tied directly to the GND pin. The inductor and the schottky diode should be placed as close as possible to the switch pin to minimize the noise coupling to the other circuits, especially the feedback network. d= 2.7-4.2V (VOUT - 1.22) • IOUT VIN • IIN This equation indicates that the white LED efficiency will be much smaller than the output efficiency of the circuit when VOUT is not very large, compared to the feedback voltage (1.22V). Vbattery Murata LQH32CN100K11 L1 10uH 0.45A DS MBR0530 Vbattery C1 4.7uF The other power is consumed by the bias resistor. To reduce this power loss, two circuits can be used, as shown in Figure 23 and Figure 24. In Figure 23, a general-purpose diode (for example, 1N4148) is used to bring the voltage across the bias resistor to be around 0.7V. R1 is used to create a loop that provides around 100µA operating current for the diode. 3% efficiency improvement can be achieved by using this method. Jun26-07 Rev D 2.7-4.2V 5 V U1 IN 4 1 SW SP6691 SHDN FB GND 2 C2 2.2uF WLED MODULE 6 5 3 4 OUT 1.22V + 1 0.1V LMV341 2 - 3 R2 Rb 11.2K R1 1K 5.1Ω Figure 24. Improve Efficiency with Op Amp in Feedback Loop Micro Power Boost Regulator Series White LED Driver 10 © 2007 Sipex Corporation PACKAGE: PINOUTS VIN SHDN VIN 5 4 SHDN 5 4 SP6691 SP6691 5 Pin SOT-23 5 Pin TSOT 1 SW Jun26-07 Rev D 2 GND 3 1 FB SW NC 1 8 NC FB 2 SP6691 7 SHDN NC 3 8 Pin DFN 6 VIN SW 4 5 GND 2 GND Micro Power Boost Regulator Series White LED Driver 11 3 FB © 2007 Sipex Corporation Package: 8 pin DFN Jun26-07 Rev D Micro Power Boost Regulator Series White LED Driver 12 © 2007 Sipex Corporation Package: 5 pin SOT-23 Jun26-07 Rev D Micro Power Boost Regulator Series White LED Driver 13 © 2007 Sipex Corporation Package: 5 pin TSOT Jun26-07 Rev D Micro Power Boost Regulator Series White LED Driver 14 © 2007 Sipex Corporation ORDERING INFORMATION Part Number Temperature Range Package Type SP6691EK1 .......................................................... -40˚C to +85˚C ............................. 5 Pin TSOT SP6691EK1/TR ..................................................... -40˚C to +85˚C ............................ 5 Pin TSOT SP6691EK ............................................................ -40˚C to +85˚C .......................... 5 Pin SOT-23 SP6691EK/TR ....................................................... -40˚C to +85˚C ......................... 5 Pin SOT-23 SP6691ER ............................................................ -40˚C to +85˚C ............................... 8 Pin DFN SP6691ER/TR ...................................................... -40˚C to +85˚C .............................. 8 Pin DFN Available in lead free packaging. To order add "-L" suffix to part number. Example: SP6691ER/TR = standard; SP6691ER-L/TR = lead free /TR = Tape and Reel Pack quantity is 2,500 for TSOT or SOT-23 and 3,000 for DFN. For further assistance: Email: WWW Support page: Sipex Application Notes: [email protected] http://www.sipex.com/content.aspx?p=support http://www.sipex.com/applicationNotes.aspx Solved by Sipex Corporation TM 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. Jun26-07 Rev D Micro Power Boost Regulator Series White LED Driver 15 © 2007 Sipex Corporation