AIC2322 2A 550k/1.1MHz Synchronous PWM Step-Down Converter FEATURES DESCRIPTION 2.5V to 6V Input Voltage Range Adjustable Output Voltage from 0.8V to Vin 2.0A Guaranteed Output Current 94% Efficiency at Heavy Load (Vin=5V, Vout=3.3V, Iout=2.0A) Low RDS(ON) Internal Switches: 110mΩ No Schottky Diode Required 100% Duty Cycle in Low Dropout Operation Fixed 550k/1.1MHz Operating Frequency Optional Soft-Start Internal Fixed 1ms SoftStart The AIC2322 is a low-noise, pulse-widthmodulated (PWM), DC-DC step-down converter. The device features an internal synchronous rectifier for high efficiency; it requires no external Schottky diode. Shutdown mode places the device in standby, reducing supply current to under 2µA. Other features of the AIC2322 include high efficiency for all load range, low dropout voltage, short circuit protection, and over temperature protection. APPLICATIONS LCD TV Multi-function Peripheral Cellular Phones CPU I/O Supplies PDAs and Handy-Terminals Battery-Operated Devices (1 Li-Ion or 3 NiMH/ NiCd). APPLICATIONS CIRCUIT 8 VIN R1 10Ω 5V 1 ON C1 10uF C2 0.1uF 5 OFF 6 VIN LX VCC FB EN REF PGND AIC2322 AIC2323 GND 7 L1 2.2uH 4 VOUT R2 50kΩ 3.3V 2 3 C4 0.1uF R3 16kΩ C3 22uF Typical Application Circuit Analog Integrations Corporation Si-Soft Research Center DS-2322G-03 20121212 3A1, No.1, Li-Hsin Rd. I , Science Park , Hsinchu 300, Taiwan , R.O.C. TEL: 886-3-5772500 FAX: 886-3-5772510 www.analog.com.tw 1 AIC2322 PIN CONFIGURATION PIN CONFIGURATION AIC2322-XXXXXX PACKING TYPE TR: TAPE & REEL TB: TUBE PACKAGE TYPE S8: SOP-8 G: Green Package SOP-8 TOP VIEW VCC 1 8 2 7 GND 3 6 4 5 REF FB A: 1.1MHz B: 550kHz VIN LX PGND EN Example: AIC2322-AGS8TR Fixed 1.1MHz Operating Frequency With GREEN SOP-8 Package and TAPE & REEL Packing Type ABSOLUTE MAXIMUM RATINGS Supply Input Volatge, VCC, VIN -0.3V to 6.5V LX Pin Switch Voltage -0.3V to (VIN + 0.3V) Other I/O Pin Voltage -0.3V to (VCC + 0.3V) +/-0.3 V PGND to GND -40C to 85C Operating Ambient Temperature Range TA Operating Maximum Junction Temperature TJ 150C -65C to 150C Storage Temperature Range TSTG 260C Lead Temperature (Soldering 10 Sec.) Thermal Resistance Junction to Case SOP-8 40C/W Thermal Resistance Junction to Ambient SOP-8 160C/W Latch-Up HBM (Human Body Mode) 200mA 4kV (Assume no Ambient Airflow, no Heatsink) Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. 2 AIC2322 ELECTRICAL CHARACTERISTICS (TA=25C, VIN=3.3V, unless otherwise specified.) (Note1) PARAMETER CONDITIONS Input Voltage Range Under Voltage Lockout Thresh- VCC Rising old VCC Falling Output Adjustment Range SYMBOL MIN VIN 2.5 TYP MAX UNITS 6 V VUVLO(R) 2.3 V VUVLO(F) 2.1 V VOUT 0.8 VIN V 2 A Shutdown Current VEN = 0V ISD 1 Quiescent Current IOUT = 0A, VFB = 1V No Switching IQ 550 Standby Current IOUT = 0A, Switching ISB 600 900 A 0.8 0.816 V Feedback Reference Voltage VOUT Line Regulation VREF VIN = 2.5V to 5.5V, IOUT=0A 0.784 -2 FB Leakage Current IFB 0.1 EN Supply Current IEN 3.5 A 2 % 0.2 A A En Logic High 1.5 VCC V EN Logic Low 0 0.5 V P-Channel On-Resistance VIN = 3.3V RDSH(ON) 110 m N-Channel On-Resistance VIN = 3.3V RDSL(ON) 80 m Switch Leakage Current VEN = 0V, VIN = 5.5V Peak Inductor Current 0.1 1 A IPK 2.6 3.4 Oscillator Frequency (A Version) fOSCA 920 1100 1280 kHz Oscillator Frequency (B Version) fOSCB 468 550 632 kHz Maximum Duty Cycle DMAX 100 Thermal Shutdown Trip Point TOTP 150 °C Thermal Shutdown Hysteresis TOTP_HYS 25 °C ISS 4 A Soft-Start Charge Current A % Note 1: Specifications are production tested at TA=25C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with Statistical Quality Controls (SQC). 3 AIC2322 TYPICAL PERFORMANCE CHARACTERISTICS (C1=10μF,C3=22μF,L1=2.2μH,TA=25℃,unless otherwise noted) VIN=5.5V VIN=4.2V VIN=5.5V VIN=3.3V VIN=2.5V VIN=4.2V (VCC=VIN,VOUT=1.8V) VIN=5V (VCC=VIN,VOUT=3.3V) Fig. 1 Efficiency vs Load Current Fig. 2 Efficiency vs Load Current VIN=VCC=3.3V,VOUT=1.8V,ILOAD=1.5A VIN=VCC=3.3V,VOUT=1.8V,ILOAD=1.5A ILX VLX VOUT OUT Ripple VEN Fig. 3 Switching Waveform Fig. 4 Soft Start Waveform VIN=VCC=3.3V,VOUT=0.8V,ILOAD=1.5A VEN VOUT VLX VEN VOUT Fig. 5 Soft Start Waveform Fig. 6 Shoutdown Waveform 4 AIC2322 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) VIN=VCC=5V,VOUT=1.5V,ILOAD=0.5A to 1A VIN=VCC=5V,VOUT=2.5V,ILOAD=0.5A to 1A OUT Ripple OUT Ripple ILOAD ILOAD Fig. 7 Load Transient Response Fig. 8 Load Transient Response Fig. 9 Switching Frequence vs Input Voltage Fig. 10 Output Voltage Deviation vs Input Voltage 5 AIC2322 BLOCK DIAGRAM Functional Block Diagram of AIC2322 PIN DESCRIPTIONS Pin No. 1 2 3 Pin Name VCC REF GND 4 FB 5 EN 6 7 8 PGND LX VIN Pin Function Signal Input Supply. Decouple this pin to GND with a capacitor. Normally VCC is equal to VIN. Internal Reference Voltage. Decouple this pin to GND with a capacitor. Signal Ground. All small-signal components and compensation components should connect to this ground, which in turn connects to PGND at one point. Feedback Pin. This pin receives the feedback voltage from a resistive divider connect across the output. Enable Pin. Connect to logic high in normal operation. Forcing this pin to GND cause the device to be shutdown. Power Ground. Connect this pin to the negative terminal of CIN and COUT. Internal Power MOSFET Switches Output. Connect this pin to the inductor. Power Input Supply. Decouple this pin to PGND with a capacitor. 6 AIC2322 APPLICATION INFORMATION Operation frequency ensures the inductor current has more time The AIC2322 is a low-noise step-down DC/DC to discharge, thereby preventing inductor current converter with current-mode PWM control architecture. runaway. The switching frequency will automatically It features an internal synchronous rectifier, which return to its designed value while short circuit condition eliminates the external Schottky diode and increases is released. efficiency. During normal operation, the AIC2322 can Shutdown regulate its output voltage through a feedback control By connecting the EN pin to GND, the AIC2322 can be circuit, which is composed of an error amplifier; a shut down to reduce the supply current to 2A (typical). current At this operation mode, the output voltage of step- comparator and several control signal generators. By comparing the feedback voltage to the down converter is equal to 0V. reference voltage of 0.8V, the error amplifier varies its 100% Duty Cycle Operation output voltage. The output voltage of the error amplifier When the input voltage approaches the output voltage, is compared with the summing signal of current the AIC2322 smoothly transits to 100% duty cycle sensing signal and slope compensation signal to operation. This allows AIC2322 to regulate the output determine the duty cycle of internal main power switch voltage until AIC2322 completely enters 100% duty (P-channel MOSFET). While the main power switch is cycle operation. In 100% duty cycle mode, the output turned on, the synchronous power switch (N-channel voltage is equal to the input voltage minus the voltage, MOSFET) will be turned off through anti-short-through which is the drop across the main power switch. block. Similarly, when the main power switch is turned The AIC2322 achieves 100% duty cycle operation by off, the synchronous power switch will be turned on extending the turn-on time of the main power switch. If until the inductor current starts to reverse or the the summing signal of current sensing signal and slope beginning of the next switching cycle. compensation signal does not reach the output voltage Current Limitation level of the error amplifier at the end of 90% switching The AIC2322 provides current limit function by using period, the main power switch is continuously turned an internal sensing resistor. When the main power on and the oscillator remains off until the summing switch turns on, current follows through the internal signal sensing resistor. And current amplifier senses the compensation signal reaches the output voltage level voltage, which crosses the resistor, and amplifies it. of the error amplifier. After the summing signal of While the sensed voltage gets higher than reference current sensing signal and slope compensation signal voltage, the current limitation function is activated. reaches the output voltage level of the error amplifier, While the current limitation function is activated, the the main power switch is turned off and the duty cycle will be reduced to limit the output power to synchronous power switch is turned on for a constant protect the internal power switches. off time. At the end of the constant off time, the next Short Circuit Protection switching cycle is begun. While the input voltage While the output is shorted to ground, the switching approaches frequency of AIC2322 will be reduced to one fourth of frequency decreases gradually to smoothly transit to the normal switching frequency. This lower switching 100% duty cycle operation. of current the sensing output signal voltage, and the slope switching 7 AIC2322 If input voltage is very close to output voltage, the ripple can be expressed as: switching mode goes from pure PWM mode to 100% VOUT duty cycle operation. During this transient state mentioned above, large output ripple voltage may appear on output terminal. I L ESR I L 8 f OSC COUT For lower output voltage ripple, the use of low ESR ceramic capacitor is recommended. The tantalum Components Selection capacitor can also be used well, but its ERS is larger Inductor The inductor selection depends on the current ripple of than that of ceramic capacitor. inductor, the input voltage and the output voltage. capacitors, X5R and X7R types are recommended L VOUT f OSC I L VOUT 1 VIN When choosing the input and output ceramic because they retain their capacitance over wider ranges of voltage and temperature than other types. Accepting a large current ripple of inductor allows the use of a smaller inductance. However, higher current ripple of inductor can cause higher output ripple voltage and large core loss. By setting an acceptable Output Voltage Programming By connecting a resistive divider R2 and R3, the output voltage of AIC2322 step-down converter can be set. VOUT can be calculated as: obtained from above equation. R VOUT 0.8 1 2 R3 In addition, it is important to ensure the inductor The resistive divider should sit as close to VFB pin as saturation current exceeds the peak value of inductor possible. current in application to prevent core saturation. The Layout Consideration current ripple of inductor, a suitable inductance can be peak value of inductor current can be calculated according to the following equation. I PEAK VOUT VOUT 1 I OUT max 2 f OSC L VIN In order to ensure a proper operation of AIC2322, the following points should be managed comprehensively. Input Capacitor and Output Capacitor To prevent the high input voltage ripple and noise 1. The input capacitor and VIN should be placed as close as possible to each other to reduce the input voltage ripple and noise. 2. The output loop, which is consisted of the inductor, resulted from high frequency switching, the use of low the internal main power switch, the internal ESR ceramic capacitor for the maximum RMS current synchronous power switch and the output capaci- is recommended. The approximated RMS current of tor, should be kept as small as possible. the input capacitor can be calculated according to the following equation. I CINRMS VOUT VIN VOUT I L2 2 I OUT ( MAX ) VIN2 12 The selection of output capacitor depends on the required output voltage ripple. The output voltage 3. The routes with large current should be kept short and wide. 4. Logically the large current on the converter should flow at the same direction. 5. The VFB pin should be connected to the feedback resistors directly and the route should be away from the noise sources. 8 AIC2322 PHYSICAL DIMENSIONS (unit: mm) SOP-8 Package h X 45° A A SEE VIEW B A e H E D WITH PLATING 0.25 C A1 B GAUGE PLANE SEATING PLANE θ L VIEW B BASE METAL SECTION A-A Note: 1. Refer to JEDEC MS-012AA. 2. Dimension "D" does not include mold flash, protrusions or gate burrs. Mold flash, protrusion or gate burrs shall not exceed 6 mil per side . 3. Dimension "E" does not include inter-lead flash or protrusions. 4. Controlling dimension is millimeter, converted inch dimensions are not necessarily exact. S Y M B O L SOP-8 MILLIMETERS MIN. MAX. A 1.35 1.75 A1 0.10 0.25 B 0.33 0.51 C 0.19 0.25 D 4.80 5.00 E 3.80 4.00 e 1.27 BSC H 5.80 6.20 h 0.25 0.50 L 0.40 1.27 θ 0° 8° Note: Information provided by AIC is believed to be accurate and reliable. However, we cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AIC product; nor for any infringement of patents or other rights of third parties that may result from its use. We reserve the right to change the circuitry and specifications without notice. Life Support Policy: AIC does not authorize any AIC product for use in life support devices and/or systems. Life support devices or systems are devices or systems which, (I) are intended for surgical implant into the body or (ii) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 9