SS6896 1.4MHz Current-Mode Step-Up DC/DC Converter Features Description Fixed-frequency 1.4MHz Current-Mode PWM The operation. modulation (PWM), step-up DC/DC converter. The l Adjustable output voltage up to 30V. built-in high-voltage N-channel MOSFET allows the l Guaranteed 13V/ 200mA output with 5V Input. SS6896 to support applications with up to 30V output l Input Range 2.5V to 10V. voltage, as well as Single-Ended Primary Inductance l Maximum 0.1µA shutdown current. Converters (SEPIC) and other low-side switching l Programmable soft-start. DC/DC converters. l Works with tiny inductors and capacitors The high switching frequency (1.4MHz) permits the l Space-s aving SOT-23-6 package. use of small external components. The soft -start l SS6896 is a current-mode pulse-width function is programmable with an external capacitor, which sets the input current ramp rate. Applications l White LED Backlight. The SS6896 is available in a space-saving SOT-23-6 l OLED Driver. package. Typical Application Circuits L V IN 84 CH521S -30 C1 4.7µF C3 ZD1 1µF BZV55 -B12 11.8V~12.2V SS6896 6 IN 4 OFF ON LX SHDN FB SS GND 1 3 R2 80 VIN=4.2V 78 VIN=3.3V 76 74 72 I LED 1K Ω 2 5 82 Efficiency (%) 3.3V or 4.2V 86 D1 L: GTSK-51-150M (15 µH) L: GTSK-51-100M (10 µH) 70 R1 68 C2 0.033µ F 2 4 6 8 10 12 14 16 18 20 LED Current (mA) Fig. 1 Li-Ion Powered Driver for three white LEDs L D1 3.6V or 4.2V 80 CH521S-30 C1 4.7 µF ZD1 BZV55 -B24 23.5V~24.5V SS6896 6 OFF ON 4 IN SHDN FB SS GND 5 C2 0.033µF LX 2 1 3 R2 ILED 1KΩ R1 C3 78 1µF 76 Efficiency (%) VIN 74 72 VIN=4.2V 70 VIN=3.6V 68 66 64 L: GTSK-51-150M (15 µH) L: GTSK-51-100M (10 µH) 62 60 2 4 6 8 10 12 14 16 18 20 LED Current (mA) Fig. 2 Li-Ion Powered Driver for six white LEDs Rev.2.01 6/06/2003 www.SiliconStandard.com 1 of 12 SS6896 Ordering Information Pin Configuration SS6896CX XX SOT- 23 -6 (CG) FRONT VIEW 1: LX 2: GND 3: FB 4: SHDN 5: SS 6: IN PACKING TYPE TR: TAPE & REEL BG: BAG PACKAGE TYPE G: SOT -23-6 6 5 4 1 2 3 Example: SS6896CGTR à in SOT-23- 6 p ackage in tape and reel. l SOT -23-6 Marking Part No. Marking SS6896CG 1896 Absolute Maximum Ratings LX to GND -0.3V to +33V FB to GND -0.3V to +6V IN, SHDN -0.3V to +11V SS to GND -0.3V to +6V LX Pin RMS Current 0.6A Continuous Power Dissipation (TA = +70°C) (Note 1) 6-Pin SOT23 (derate 9.1mW/°C above +70°C) 727mW Operating Temperature Range -40°C to +85°C Junction Temperature +150°C Storage Temperature Range -65°C to +150°C Lead Temperature (soldering, 10s) +300°C Note 1: Thermal properties are specified with product mounted on PC board with one square-inch of copper area and still air. Test Circuit D1 L1 VIN 2.5V to 10V + VOUT + SS14 C1 10µF/16V SS6896 6 4 SHDN C3 IN LX SHDN FB SS R1 1 C4 10µF C5 1µF 3 GND 5 2 R2 C2 0.033µF Rev.2.01 6/06/2003 www.SiliconStandard.com 2 of 12 SS6896 Electrical Characteristics PARAMETER Input Supply Range (V IN=V SHDN =3V, FB=GND, SS=Open, T A= -40° C to 85° C, unless otherwise specified) SYMBOL CONDITIONS VIN VOUT VIN Undervoltage Lockout UVLO VIN rising, 50mV hysteresis IIN Shutdown Supply Current TYP 2.5 Output Voltage Adjust Range Quiescent Current MIN MAX UNITS 10 V 30 V 2.2 VFB = 1.3V, not switching V 0.1 0. 2 1 5 V SHDN = 0, TA = +25°C 0.01 0.5 µA V SHDN = 0 0.01 10 µA 1.23 1.255 V 21 80 nA 0.05 0.20 %/V 1800 KHz VFB = 1.0V, switching mA ERROR AMPLIFIER Feedback Regulation Set Point VFB FB Input Bias Current IFB Line Regulation 1.205 VFB = 1.24V 2.6V < VIN < 5.5V OSCILLATOR Frequency Maximum Duty Cycle fOSC 1000 1400 DC 82 86 % POWER SWITCH Steady State Output Current Io On- Resistance RDS(ON) Leakage Current ILX(OFF) Refer to Fig. 18 A VLX = 12V, TA = +25°C 1 1.4 0.1 1 VLX = 12V 10 Ω µA SOFT-START Reset Switch Resistance Charge Current VSS = 1.2V 1.5 4 100 Ω 7.0 µA 0.3 V CONTROL INPUT Input Low Voltage VIL V SHDN , VIN = 2. 5V to 10V Input High Voltage VIH V SHDN , VIN = 2. 5V to 10V SHDN Input Current Rev.2.01 6/06/2003 I SHDN V SHDN = 3V V SHDN = 0 www.SiliconStandard.com 1.0 V 25 50 0.01 0.1 µA 3 of 12 SS6896 Typical Performance Characteristics 1.50 TA=25° C 1.45 VIN=3.6V Frequency (MHz) Switching Frequency (MHz) 1.50 1.40 1.35 1.30 1.45 1.40 1.35 1.25 1.30 1.20 -40 -20 0 20 40 60 80 2 100 3 4 5 6 7 8 Temperature (° C) 10 11 10 11 Fig. 4 Frequency vs. Supply Voltage Fig. 3 Switching Frequency vs. Temperature 5.50 1.7 1.6 VIN=3.6V Output Voltage (V) 1.5 RDS(ON) (Ω) 9 Supply Voltage (V) 1.4 1.3 1.2 1.1 1.0 5.25 5.00 4.75 0.9 4.50 0.8 2 3 4 5 6 7 8 9 10 11 1 10 100 Supply Voltage (V) Output Current (mA) Fig. 5 RDSON vs. Supply Voltage Fig. 6 Load Regulation (L1=10uH) 12.5 2.4 12.0 11.5 11.0 FB=1.0V SHDN=1.0V 2.2 Supply Current (mA) Output Voltage (V) VIN =3.6V 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 10.5 Rev.2.01 6/06/2003 1 10 100 2 3 4 5 6 7 8 Output Current (mA) Supply Voltage (V) Fig. 7 Load Regulation (L1=22uH) Fig. 8 Switching Current www.SiliconStandard.com 9 4 of 12 SS6896 Typical Performance Characteristics (Continued) 90 V IN=4.2V 85 85 VIN =2.7V Efficiency (%) Supply Current (£ g A) 90 FB=1.3V SHDN=1.0V 80 75 70 80 V IN =2.5V VIN=3.6V VIN =3.3V 75 70 VOUT=5.0V 65 60 65 2 3 4 5 6 7 8 9 10 11 Supply Voltage (V) 0 100 200 300 400 500 600 Output Current (mA) Fig. 10 Efficiency vs. Output Current (L1=10µH) Fig. 9 Non-Switching Current 90 V OUT=12V VLX Efficiency (%) 85 VIN=4.2V 80 VIN =3.6V 75 VIN=5.0V VOUT V IN=3.3V 70 ILX 65 60 0 50 100 150 Output Current (mA) Fig. 11 Efficiency vs. output current (L1=22µH) Rev.2.01 6/06/2003 200 Fig. 12 Operation Wave Form (VIN=3V;VOUT=5V;L1=10µH;R1=36K;R2=12K; C3=39pF;IOUT=200mA) www.SiliconStandard.com 5 of 12 SS6896 Typical Performance Characteristics (Continued) SHDN VSW VOUT VOUT ILX ILX Fig. 13 Operation Wave Form (VIN =5V; V OUT =12V, L1=22 µH; R1=105K; R2=12K;C3=1nF;IOUT =200mA) Fig. 14 Start-Up from Shutdown (V IN =3.3V ;V OUT =13V ;RLOAD=300Ω ) VOUT V OUT ILX ILX Fig. 16 Load Step Response Fig. 15 Load Step Response (V IN =3.3V; V OUT =5V;L1=10uH; I OUT=5mA to 200mA) Rev.2.01 6/06/2003 (V IN =5V ; V OUT=12V ;L1=22uH; IOUT=5mA to 150mA) www.SiliconStandard.com 6 of 12 SS6896 Typical Performance Characteristics (Continued) 800 Maximum Output Current (mA) Feedback Voltage (V) 1.25 1.24 1.23 1.22 1.21 1.20 -50 V IN=3.6V -25 0 25 50 75 V OUT=13V 700 VOUT=9V 600 500 VOUT=5V VOUT=15V 400 300 200 100 100 2 Temperature (° C) 3 4 5 6 7 8 9 10 Supply Voltage (V) Fig. 17 Feedback Pin Voltage Fig. 18 Maximum Output current vs. Supply Voltage (L1:10µH Vo=5V,9V ; L1=22 µH Vo=13V,15V) Block Diagram VIN PWM/PFM C ontrol I9 S oft - Start R4 PWM Comparator Error Amp - + + FB Q1 Q2 1 8 R1 R2 SS 4 µA R3 C ontrol Logic SHDN D river - RC CC S lope Compensation 1.4MHz O scillator LX x1 x20 C urrent A m p x 5 + - Rev.2.01 6/06/2003 www.SiliconStandard.com RS GND 7 of 12 SS6896 Pin Descriptions PIN 1: LX - Power Connect rectifier. between to LX as Switching Connection. LX to inductor and output Keep the distance the components as close possible. PIN 2: GND - Ground. PIN 3: FB Feedback Input. Connect a resistive voltage -divider from the output to FB to set the output voltage. PIN 4: - SHDN with a slew rate of 0.1V/µs or greater. Do not leave SHDN unconnected. SHDN draws up to 50µA. PIN 5: SS - Soft -Start Input. Connect a soft -start capacitor from SS to GND in order to soft -start the converter. Leave SS open to disable the soft -start function. PIN 6: IN - Internal Bias Voltage Input. Connect IN to the input voltage source. Bypass IN to GND with a capacitor sitting as close to IN as possible. SHDN - Shutdown Input. Drive SHDN low to turn off the converter. To automatically start the converter, connect SHDN to IN. Drive Rev.2.01 6/06/2003 www.SiliconStandard.com 8 of 12 SS6896 Application Information Inductor Selection R1 = 1.23V/ILED (1) A 15µH inductor is recommended for most SS6896 applications. Although small size and high efficiency Open-Circuit Protection are major concerns, the inductor should have low In the cases of output open-circuit, when the LEDs core losses at 1.4MHz and low DCR (copper wire are disconnected from the circuit or the LEDs fail, resistance). the feedback voltage will be zero. The SS6896 will then switch to a high duty cycle resulting in a high Capacitor Selection output voltage, which may cause the SW pin The small size of ceramic capacitors makes them voltage to exceed its maximum 30V rating. A zener ideal for SS6896 applications. X5R and X7R types diode can be used at the output to limit the voltage are their on the SW pin (Fig. 20). The zener voltage should capacitance over wider ranges of voltage and be larger than the maximum forward voltage of the temperature than other types, such as Y5V or Z5U. LED string. The current rating of the zener should A 4.7µF input capacitor and a 1µF output capacitor be larger than 0.1mA. recommended because they retain are sufficient for most SS6896 applications. Dimming Control Diode Selection There are three different types of dimming control Schottky diodes, with their low forward voltage drop circuits as follows: and fast reverse recovery, are the ideal choices for SS6896 applications. The forward voltage drop of a 1. Using a PWM signal Schottky diode represents the conduction losses in PWM the diode, while the diode capacitance (CT or CD) dimming range by pulsing the LEDs on and off using represents the switching losses. For diode selection, the control signal. The LEDs operate at either zero both forward voltage drop and diode capacitance or full current, The average LED current changes need to be considered. Schottky diodes with higher with the duty cycle of the PWM signal. Typically, a current ratings usually have lower forward voltage 1kHz to 10kHz PWM signal is used. PWM dimming drop and larger diode capacitance, which can cause with the SS6896 can be accomplished two different significant switching losses at the 1.4MHz switching ways (see Fig. 21). The SHDN pin can be driven frequency of the SS6896. A Schottky diode rated at directly or a resistor can be added to drive the FB 100mA to 200mA is sufficient for most SS6896 pin. If the SHDN pin is used, increasing the duty applications. cycle will increase the LED brightness. If the FB pin brightness control provides the widest is used, increasing the duty cycle will decrease the LED Current Control brightness. Using this method, the LEDs are dimmed LED current is controlled by a feedback resistor (R1 using FB and turned off completely using SHDN . in Fig. 1). The feedback reference is 1.23V. The LED current is 1.23V/R1. In order to have accurate 2. Using a DC Voltage LED current, precision resistors are preferred (1% For some applications, the preferred method of recommended). The formula for R1 selection is brightness control uses a variable DC voltage to shown below. adjust the LED current. The dimming control using a Rev.2.01 6/06/2003 www.SiliconStandard.com 9 of 12 SS6896 DC voltage is shown in Fig. 22. As the DC voltage 3. Using a Filtered PWM Signal increases, the voltage drop on R2 increases and the The filtered PWM signal can be considered as an voltage drop on R1 decreases. adjustable DC voltage. It can be used to replace the Thus, the LED current decreases. The selection of variable DC voltage source in dimming control. The R2 and R3 should make the current from the circuit is shown in Fig. 23. variable DC source much smaller than the LED current and much larger than the FB pin bias current. For VDC range from 0V to 5V, the selection of resistors in Fig. 22 gives dimming control of LED current from 20mA to 0mA. L1 VIN D1 10µH 3V to 4.2V C3 CH521S-30 ZD1 C1 4.7µF 1µF BZV55-B20 SS6896 OFF 19.6V~20.4V 6 IN LX 1 4 SHDN FB 3 ON SS R2 IOUT=ILED=20mA GND 5 2 1K£ [ C2 0.033µF R1 62£ [ Fig. 20 White LED driver with open -circuit protection ZD1 SS6896 IN LX SHDN OFF FB 1K £ [ SS GND IN LX SHDN FB R2 R2 PWM ZD1 SS6896 1KΩ ON SS R1 GND R1 R3 3.3KΩ 62 £ [ C2 C2 0.033µF 0.033µF 82Ω PWM (a) (b) Fig. 21 Dimming-control using a PWM signal Rev.2.01 6/06/2003 www.SiliconStandard.com 10 of 12 SS6896 ZD1 SS6896 ZD1 SS6896 IN SHDN OFF SHDN FB 1K £ [ ON FB SS 1K £ [ ON SS LX R2 LX R2 OFF IN GND R1 R3 C2 82 £ [ 3.3K£ [ C2 GND R3 20mA~0mA 3.3K£ [ 0.033µ F 0.033µ F R4 4K £ [ C1 0.1 µF VDC 0V~5V Fig. 22 Dimming-control us ing a DC voltage R1 82£ [ PWM Fig. 23 Dimming-control using a filtered PWM signal Application Example L1 VIN D1 10µH 3V to 4.2V C1 4.7µF CH521S-30 C3 1µF ZD1 BZV55-B24 SS6896 23.5V~24.5V 6 4 OFF ON LX IN SHDN FB GND SS 5 2 1 3 R2 1K£ [ IOUT=ILED=20mA C2 0.033µF R1 R3 62£ [ 62£ [ Fig. 24 Li- Ion powered driver for eight white LEDs with open -circuit protection Rev.2.01 6/06/2003 www.SiliconStandard.com 11 of 12 SS6896 Physical Dimensions l SOT-23-6 (unit: mm) C D L H E θ1 e A A2 SYMBOL MIN MAX A 1.00 1.30 A1 — 0.10 A2 0.70 0.90 b 0.35 0.50 C 0.10 0.25 D 2.70 3.10 E 1.60 2.00 e A1 b 1.90 (TYP) H 2.60 3.00 L 0.37 — θ1 1° 9° Information furnished by Silicon Standard Corporation is believed to be accurate and reliable. However, Silicon Standard Corporation makes no guarantee or warranty, express or implied, as to the reliability, accuracy, timeliness or completeness of such information and assumes no responsibility for its use, or for infringement of any patent or other intellectual property rights of third parties that may result from its use. Silicon Standard reserves the right to make changes as it deems necessary to any products described herein for any reason, including without limitation enhancement in reliability, functionality or design. No license is granted, whether expressly or by implication, in relation to the use of any products described herein or to the use of any information provided herein, under any patent or other intellectual property rights of Silicon Standard Corporation or any third parties. Rev.2.01 6/06/2003 www.SiliconStandard.com 12 of 12