AIC2302 700mA Synchronous PWM Step-Down DC/DC Converter FEATURES DESCRIPTION 2.5V to 5.5V Input Voltage Range 700mA Guaranteed Output Current Up to 95% Efficiency Low RDS(ON) Internal Switche: 280mΩ No Schottky Diode Required 100% Duty Cycle in Low Dropout Operation Operating Frequency: 1.5MHz Accurate Reference 0.6V Provides Low Output Voltages APPLICATIONS LCD TV Multi-function Peripheral Cellular Phones CPU I/O Supplies Cordless Phones PDAs and Handy-Terminals Battery-Operated Devices (1 Li-Ion or 3 NiMH/ NiCd) The AIC2302 is a low-noise, pulse-widthmodulated (PWM), DC-DC step-down converter. The device is available in an adjustable version and fixed output voltages of 1.0V, 1.2V, 1.8V, and 3.3V. 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 1µA. Other features of the AIC2302 include high efficiency, low dropout voltage, short circuit protection, over temperature protection, and over voltage protection. It is available in a small 5 pins SOT23 package. APPLICATIONS CIRCUIT Fig. 1 Fixed Step-Down DC/DC Converter Analog Integrations Corporation Si-Soft Research Center DS-2302G-01 20120531 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 AIC2302 Fig. 2 Adjustable Step-Down DC/DC Converter ORDERING INFORMATION AI C2302 -XX X XX XX P IN CO NFIG UR ATIO N P ACK ING TY PE TR: T APE & REE L B G: BA G TOP VIEW SOT-23-5 V OU T V IN 5 4 P ACK AG E TYP E V 5: S O T-2 3-5 1 G : G reen Pa ckag e 2 3 EN GN D LX Fixed version O UTP UT VO LTA G E DE FA ULT: Adj. -10: 1.0V -12 : 1.2 V -18 : 1.8 V -33 : 3.3 V T OP V IEW SOT -2 3-5 FB VIN 5 4 1 Exam ple: AIC2 302-3 3G V5TR 3.3 V O utp ut V ers ion , 2 3 EN G ND L X A djusta ble ve rsion in S OT-23 -5 G re en P ac kage & Tape & Re el Packin g Type AIC2 302G V 5TR Ad justa ble Ve rs io n, in S OT-23 -5 G re en P ac kage & Tape & Re el Packin g Type 2 AIC2302 ORDERING INFORMATION (Continuous) Marking (Fixed Version) Part No. Marking AIC2302-10GV5 HR10G AIC2302-12GV5 HR12G AIC2302-18GV5 HR18G AIC2302-33GV5 HR33G Marking (Adjustable Version) Part No. Marking AIC2302GV5 2302G 3 AIC2302 ABSOLUTE MAXIMUM RATINS VIN, LX Voltage 6V -0.3 V to VIN EN, FB Pin Voltage -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 SOT-23-5 115C/W Thermal Resistance Junction to Ambient SOT-23-5 250C/W (Assume no Ambient Airflow, no Heatsink) Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. 4 AIC2302 ELECTRICAL CHARACTERISTICS (TA=25C, VIN=3.6V unless otherwise specified.) (Note 1) PARAMETER CONDITIONS SYMBOL MIN VIN Output Adjustment Range Reference Voltage Input Voltage Range TYP MAX UNITS 2.5 5.5 V VOUT 0.6V VIN-0.3V V VREF 0.588 0.612 V IFB -50 50 nA 0.6 FB Input Current VFB = VIN P-Channel On-Resistance IOUT = 0.2A PRDS(ON) 280 390 m N-Channel On-Resistance IOUT = 0.2A NRDS(ON) 250 390 m LX Leakage Current VLX=0V or VLX=3.6V 1 uA Peak Inductor Current VIN = 5V IPK Quiescent Current IOUT = 0mA, VFB=0.78V IQ 65 85 A Shutdown Supply Current EN = GND ISHDN 0.1 1 A EN High-Level Input Voltage VIN=2.5V to 5.5V VEN_H EN Low-Level Input Voltage VIN=2.5V to 5.5V VEN_L -1 0.9 1.1 A 1.5 Oscillator Frequency fOSC 1.2 Maximum Duty Cycle DMAX 100 V 1.5 0.4 V 1.8 MHz % Thermal Shutdown Temperature 150 °C Thermal Shutdown Hysteresis 25 °C 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). 5 AIC2302 TYPICAL PERFORMANCE CHARACTERISTICS VIN=5V VIN=5V VIN=3.3V VIN=2.5V Fig. 3 Efficiency vs. Input Voltage Fig. 4 Efficiency vs. Input Voltage t Fig. 5 Oscillator Frequency vs. Temperature Fig. 6 Oscillator Frequency vs. Input Voltage Fig. 7 RDS(ON) vs. Input Voltage Fig. 8 Supply Current vs. Input Voltage 6 AIC2302 Fig. 9 Current Limit vs. Input Voltage Fig. 10 Output Voltage vs. Temperaturet Fig. 11 Load Transient Response Fig. 12 Load Transient Response Fig. 13 Load Transient Response Fig. 14 Load Transient Response 7 AIC2302 BLOCK DIAGRAM Functional Block Diagram of AIC2302 PIN DESCRIPTIONS Pin Name Pin Function NC No Internal Connect (Floating or Connecting to GND). EN Chip Enable (Active High). VIN Power Input. LX Pin for Switching. GND Ground. FB/VOUT Feedback/Output Voltage Pin. 8 AIC2302 APPLICATION INFORMATION Operation frequency of AIC2302 will be reduced to one third of The AIC2302 is a low-noise step-down DC/DC the normal switching frequency. This lower switching converter with current-mode PWM control architecture. frequency ensures the inductor current has more time It features an internal synchronous rectifier, which to discharge, thereby preventing inductor current eliminates the external Schottky diode and increases runaway. The switching frequency will automatically efficiency. During normal operation, the AIC2302 can return to its designed value while short circuit condition regulate its output voltage through a feedback control is released. circuit, which is composed of an error amplifier; a Shutdown current comparator and several control signal generators. By comparing the feedback voltage to the reference voltage of 0.6V, the error amplifier varies its output voltage. The output voltage of the error amplifier By connecting the EN pin to GND, the AIC2302 can be shut down to reduce the supply current to 0.1A (typical). At this operation mode, the output voltage of step-down converter is equal to 0V. is compared with the summing signal of current sensing signal and slope compensation signal to 100% Duty Cycle Operation determine the duty cycle of internal main power switch When the input voltage approaches the output voltage, (P-channel MOSFET). While the main power switch is the AIC2302 smoothly transits to 100% duty cycle turned on, the synchronous power switch (N-channel operation. This allows AIC2302 to regulate the output MOSFET) will be turned off through anti-short-through voltage until AIC2302 completely enters 100% duty block. Similarly, when the main power switch is turned cycle operation. In 100% duty cycle mode, the output off, the synchronous power switch will be turned on voltage is equal to the input voltage minus the voltage, until the inductor current starts to reverse or the which is the drop across the main power switch. beginning of the next switching cycle. In order to The AIC2302 achieves 100% duty cycle operation by achieve better efficiency and prevent overcharging the extending the turn-on time of the main power switch. If output capacitor. the summing signal of current sensing signal and slope Current Limitation The AIC2302 provides current limit function by using an internal sensing resistor. When the main power switch turns on, current follows through the internal sensing resistor. And current amplifier senses the voltage, which crosses the resistor, and amplifies it. While the sensed voltage gets higher than reference voltage, the current limitation function is activated. While the current limitation function is activated, the duty cycle will be reduced to limit the output power to protect the internal power switches. Short Circuit Protection While the output is shorted to ground, the switching compensation signal does not reach the output voltage level of the error amplifier at the end of 90% switching period, the main power switch is continuously turned on and the oscillator remains off until the summing signal of current sensing signal and slope compensation signal reaches the output voltage level of the error amplifier. After the summing signal of current sensing signal and slope compensation signal reaches the output voltage level of the error amplifier, the main power switch is turned off and the synchronous power switch is turned on for a constant off time. At the end of the constant off time, the next switching cycle is begun. While the input voltage approaches the output voltage, the switching 9 AIC2302 frequency decreases gradually to smoothly transit to ripple can be expressed as: 100% duty cycle operation. VOUT If input voltage is very close to output voltage, the IL ESR IL 8 fOSC COUT switching mode goes from pure PWM mode to 100% For lower output voltage ripple, the use of low ESR duty cycle operation. During this transient state ceramic capacitor is recommended. The tantalum mentioned above, large output ripple voltage may capacitor can also be used well, but its ERS is larger appear on output terminal. than that of ceramic capacitor. When Components Selection choosing the input and output ceramic capacitors, X5R and X7R types are recommended Inductor The inductor selection depends on the current ripple of inductor, the input voltage and the output voltage. VOUT L fOSC IL because they retain their capacitance over wider ranges of voltage and temperature than other types. Output Voltage Programming (AIC2302 Adjustable Version Only) By connecting a resistive divider R1 and R2, the output V 1 OUT VIN Accepting a large current ripple of inductor allows the voltage of AIC2302 step-down converter can be set. use of a smaller inductance. However, higher current VOUT can be calculated as: ripple of inductor can cause higher output ripple R VOUT 0.6 1 1 R2 voltage and large core loss. By setting an acceptable current ripple of inductor, a suitable inductance can be obtained from above equation. The resistive divider should sit as close to VFB pin as possible. In addition, it is important to ensure the inductor saturation current exceeds the peak value of inductor Layout Consideration current in application to prevent core saturation. The In order to ensure a proper operation of AIC2302, the peak value of inductor current can be calculated following points should be managed comprehensively. according to the following equation. 1. The input capacitor and VIN should be placed as IPEAK IOUT max close as possible to each other to reduce the input VOUT V 1 OUT 2 fOSC L VIN voltage ripple and noise. 2. The output loop, which is consisted of the inductor, Input Capacitor and Output Capacitor To prevent the high input voltage ripple and noise resulted from high frequency switching, the use of low ESR ceramic capacitor for the maximum RMS current is recommended. The approximated RMS current of the input capacitor can be calculated according to the following equation. 2 ICINRMS IOUT (MAX ) the internal main power switch, the internal synchronous power switch and the output capacitor, should be kept as small as possible. 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. VOUT VIN VOUT 2 VIN IL2 5. The VFB pin should be connected to the feedback 12 resistors directly and the route should be away The selection of output capacitor depends on the from the noise sources. required output voltage ripple. The output voltage 10 AIC2302 PHYSICAL DIMENSIONS D E1 SOT-23-5 A A E e e1 SEE VIEW B WITH PLATING c A A2 b SECTION A-A A1 BASE METAL 0.25 S Y M B O L GAUGE PLANE SEATING PLANE L1 θ L VIEW B Note : 1. Refer to JEDEC MO-178AA. 2. Dimension "D" does not include mold flash, protrusions or gate burrs. Mold flash, protrusion or gate burrs shall not exceed 10 mil per side. 3. Dimension "E1" does not include inter-lead flash or protrusions. 4. Controlling dimension is millimeter, converted inch dimensions are not necessarily exact. A SOT-23-5 MILLIMETERS MIN. MAX. 0.95 1.45 A1 0.00 0.15 A2 0.90 1.30 b 0.30 0.50 c 0.08 0.22 D 2.80 3.00 E 2.60 3.00 E1 1.50 1.70 e 0.95 BSC e1 1.90 BSC L θ 0.60 0.30 L1 0.60 REF 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. 11