AIC1896. Efficiency (%) I LED R1. Fig. 1 Li-Ion Powered Driver for three white LEDs

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1 .MHz SOT2 Current-Mode Step-Up DC/DC Converter FEATURES Fixed Frequency.MHz Current-Mode PWM Operation. Adjustable Output Voltage up to 0V. Guaranteed V/ 200mA Output with 5V Input. 2.5V to 0V Input Range. Maximum 0.µA Shutdown Current. Programmable Soft-Start. Tiny Inductor and Capacitors are allowed. Space-Saving SOT-2-6 Package. APPLICATIONS White LED Backlight. OLED Driver. DESCRIPTION is a current-mode pulse-width modulation (PWM), step-up DC/DC Converter. The built-in high voltage N-channel MOSFET allows for step-up applications with up to 0V output voltage, as well as for Single Ended Primary Inductance Converter (SEPIC) and other low-side switching DC/DC converter. The high switching frequency (.MHz) allows the use of small external components. The Soft-Start function is programmable with an external capacitor, which sets the input current ramp rate. The is available in a space-saving SOT-2-6 package. TYPICAL APPLICATION CIRCUIT V.V or.2v C.7µF OFF ON L D CH52S-0 BZV55-B2.8V~2.2V KΩ C µf I LED Efficiency (%) V =.2V V =.V L: GTSK-5-50M (5µH) L: GTSK-5-00M (0µH) LED Current (ma) Fig. Li-Ion Powered Driver for three white LEDs Analog Integrations Corporation F, 9 Industry E. 9th Rd, Science-Based Industrial Park, Hsinchu, Taiwan DS TEL: FAX: This datasheet has been downloaded from at this page

2 V.6V or.2v C.7µF OFF ON L D CH52S-0 BZV55-B2 2.5V~2.5V KΩ I LED C µf Efficiency (%) V =.2V V =.6V L: GTSK-5-50M (5µH) L: GTSK-5-00M (0µH) LED Current (ma) ORDERG FORMATION Fig. 2 Li-Ion Powered Driver for six white LEDs -CXXX PACKG TYPE TR: TAPE & REEL BG: BAG PACKAGE TYPE G: SOT-2-6 Example: -CGTR in SOT-2-6 Package & Tape & Reel Packing Type P CONFIGURATION SOT-2-6 (CG) FRONT VIEW : 2: : : 5: 6: SOT-2-6 Marking Part No. Marking CG 896 2

3 ABSOLUTE MAXIMUM RATGS to -0.V to +V to -0.V to +6V, -0.V to +V to -0.V to +6V Pin RMS Current 0.6A Continuous Power Dissipation (T A = +70 C) (Note ) 6-Pin SOT2 (derate 9.mW/ C above +70 C) 727mW Operating Temperature Range -0 C to +85 C Junction Temperature +50 C Storage Temperature Range -65 C to +50 C Lead Temperature (soldering, 0s) +00 C Note : Thermal properties are specified with product mounted on PC board with one square-inch of copper area and still air.

4 ELECTRICAL CHARACTERISTICS (V =V =V, =, =Open, T A =-0 C to 85 C, Unless otherwise specified) PARAMETER SYMBOL CONDITIONS M TYP MAX UNITS Input Supply Range V V Output Voltage Adjust Range V OUT 0 V V Undervoltage Lockout UVLO V rising, 50mV hysteresis 2.2 V Quiescent Current Shutdown Supply Current ERROR AMPLIFIER I V =.V, not switching V =.0V, switching 5 ma V = 0, T A = +25 C µa V = µa Feedback Regulation Set Point V V Input Bias Current I V =.2V 2 80 na Line Regulation 2.6V < V < 5.5V %/V OSCILLATOR Frequency f OSC KHz Maximum Duty Cycle DC % POWER SWITCH Steady State Output Current Io Refer to Fig. 8 A On-Resistance R DS(ON). Ω V = 2V, T A = +25 C 0. Leakage Current I (OFF) V = 2V 0 SOFT-START Reset Switch Resistance 00 Ω Charge Current V =.2V µa CONTROL PUT Input Low Voltage V IL V, V = 2.5V to 0V 0. V Input High Voltage V IH V, V = 2.5V to 0V.0 V V = V Input Current I V = µa µa

5 TYPICAL PERFORMANCE CHARACTERISTICS Switching Frequency (MHz) V =.6V Frequency (MHz) T A =25 C Temperature ( C) Fig. Switching Frequency vs. Temperature Supply Voltage (V) Fig. Frequency vs. Supply Voltage RDS(ON) (Ω) Output Voltage (V) V =.6V Supply Voltage (V) Fig. 5 R DSON vs. Supply Voltage Output Current (ma) Fig. 6 Load Regulation Output Voltage (V) V =.6V Supply Current (ma) =.0V =.0V Output Current (ma) Fig. 7 Load Regulation Supply Voltage (V) Fig. 8 Load Regulation 5

6 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Supply Current (µa) =.V =.0V Efficiency (%) V =2.7V V =2.5V V =.2V V =.6V V =.V V OUT =5.0V Supply Voltage (V) Fig. 9 Non-Switching Current Output Current (ma) Fig. 0 Efficiency vs. Output Current V =5.0V V Efficiency (%) V =.V V =.6V V =.2V V OUT =2V V OUT I Output Current (ma) Fig. Efficiency vs. Output Current Fig. 2 Operation Wave Form (V =V;V OUT =5V;L=0µH;=6K;=2K; C=9pF;I OUT =200mA) 6

7 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) V SW V OUT V OUT I I Fig. Operation Wave Form (V =5V; V OUT =2V, L=22µH; =05K; =2K;C=nF;I OUT =200mA) Fig. Start-Up from Shutdown (V =.V ;V OUT =V ;R LOAD =00Ω) V OUT V OUT I I Fig. 5 Load Step Response (V =.V; V OUT =5V; I OUT =5mA to 200mA) Fig. 6 Load Step Response (V =5V ; V OUT =2V ; I OUT =5mA to 50mA) 7

8 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Feedback Voltage (V) V =.6V Maximum Output Current (ma) V OUT=5V V OUT=9V V OUT=V V OUT=5V Temperature ( C) Fig. 7 Feedback Pin Voltage Supply Voltage (V) Fig. 8 Maximum Output current vs. Supply Voltage L D V 2.5V to 0V C 0µF/6V + 6 U C + C 0µF C5 µf V OUT 5 2 Fig. 9. Test circuit of figure 9~8. 8

9 BLOCK DIAGRAM V R Q R Q Error Amp RC PWM Comparator + - PWM/PFM Control Control Logic Driver Soft- Start I9 µa CC Slope Compensation Current Amp x 5.MHz Oscillator + - x RS x20 P DESCRIPTIONS P : - Power Switching Connection. Connect to inductor and output rectifier. Keep the distance between the components as close to as possible. P 2: - Ground. P : - Feedback Input. Connect a resistive voltage-divider from the output to to set the output voltage. P : - Shutdown Input. Drive low to turn off the converter. To automatically start the converter, connect to. Drive with a slew rate of 0.V/µs or greater. Do not leave unconnected. draws up to 50µA. P 5: - Soft-Start Input. Connect a soft-start capacitor from to in order to soft-start the converter. Leave open to disable the soft-start function. P 6: - Internal Bias Voltage Input. Connect to the input voltage source. Bypass to with a capacitor sitting as close to as possible. 9

10 APPLICATION FORMATION Inductor Selection A 5µH inductor is recommended for most applications. Although small size and high efficiency are major concerns, the inductor should have low core losses at.mhz and low DCR (copper wire resistance). Capacitor Selection The small size of ceramic capacitors makes them ideal for applications. X5R and X7R types are recommended because they retain their capacitance over wider ranges of voltage and temperature than other types, such as Y5V or Z5U. A.7µF input capacitor and a µf output capacitor are sufficient for most applications. Diode Selection Schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for applications. The forward voltage drop of a Schottky diode represents the conduction losses in the diode, while the diode capacitance (CT or CD) represents the switching losses. For diode selection, both forward voltage drop and diode capacitance need to be considered. Schottky diodes with higher current ratings usually have lower forward voltage drop and larger diode capacitance, which can cause significant switching losses at the.mhz switching frequency of. A Schottky diode rated at 00mA to 200mA is sufficient for most applications. LED Current Control LED current is controlled by feedback resistor ( in Fig. ). The feedback reference is.2v. The LED current is.2v/. In order to have accurate LED current, precision resistors are preferred (% recommended). The formula for selection are shown below. =.2V/I LED () Open-Circuit Protection In the cases of output open circuit, when the LEDs are disconnected from the circuit or the LEDs fail, the feedback voltage will be zero. will then switch to a high duty cycle resulting in a high output voltage, which may cause SW pin voltage to exceed its maximum 0V rating. A zener diode can be used at the output to limit the voltage on SW pin (Fig. 20). The zener voltage should be larger than the maximum forward voltage of the LED string. The current rating of the zener should be larger than 0.mA. Dimming Control There are three different types of dimming control circuits as follows:. Using a pwm signal PWM brightness control provides the widest dimming range by pulsing the LEDs on and off using the control signal. The LEDs operate at either zero or full current, The average LED current changes with the duty cycle of the PWM signal. Typically, a khz to 0kHz PWM signal is used. PWM dimming with the can be accomplished two different ways (see Fig. 2). The pin can be driven directly or a resistor can be added to drive the pin. If the pin is used, increasing the duty cycle will increase the LED brightness. If the pin is used, increasing the duty cycle will decrease the brightness. Using this method, the LEDs are dimmed using and turned off completely using. 0

11 2. Using a DC Voltage For some applications, the preferred method of brightness control uses a variable DC voltage to adjust the LED current. The dimming control using a DC voltage is shown in Fig. 22. As the DC voltage increases, the voltage drop on increases and the voltage drop on decreases. Thus, the LED current decreases. The selection of and R should make the current from the variable DC source much smaller than the LED current and much larger than the 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.. Using a Filtered PWM Signal The filtered PWM signal can be considered as an adjustable DC voltage. It can be used to replace the variable DC voltage source in dimming control. The circuit is shown in Fig. 2. V V to.2v C.7µF U L 0µH D CH52S-0 BZV55-B20 9.6V~20.V C µf 6 OFF ON 5 2 KΩ 62Ω I OUT =I LED =20mA Fig. 20 White LED Driver with Open-Circuit Protection PWM K 62 OFF ON K R 0K 62 PWM (a) Fig. 2 Dimming Control Using a PWM Signal (b)

12 OFF ON K R.K 68 20mA~0mA OFF ON R K.K R K 68 VDC 0V~5V C 0.µF PWM Fig. 22 Dimming Control Using a DC Voltage Fig. 2 Dimming Control Using a Filtered PWM Signal APPLICATION EXAMPLES V V to.2v C.7µF L 0µH U D CH52S-0 BZV55-B2 2.5V~2.5V C µf 6 OFF ON 5 2 KΩ 62Ω R 62Ω I OUT =I LED =20mA Fig. 2 Li-Ion Powered Driver for eight White LEDs with Open-Circuit Protection 2

13 PHYSICAL DIMENSIONS SOT-2-6 (unit: mm) D C SYMBOL M MAX H E L A.00.0 A 0.0 A b e θ C D A2 A E e.90 (TYP) b A H L 0.7 θ 9