AIC2309 1A Dual Synchronous Step-down DC/DC Converter FEATURES DESCRIPTION Dual 1A Output 2.5V to 5.5V Input Range Accurate Reference 0.6V Provides Low Output Voltages Adjustable Output Voltage Up to 95% Efficiency Stable with Low ESR Output Ceramic Capacitors No Schottky Diode Required. 65µA Quiescent Current per Channel. 100% Duty Cycle in Low Dropout Operation. 1.5MHz Fixed-Frequency PWM Operation APPLICATIONS Digital Still Cameras Cellular Phones Wireless and DSL Modems Notebook Chipset Supplies. PDAs and Handy-Terminals Battery-Operated Devices (1 Li-Ion or 3 NiMH/ NiCd). The AIC2309 is a dual output, low-noise, pulse-width-modulated (PWM), DC-DC stepdown converter. It powers logic and transmitters in small wireless systems such as cellular phones, communicating PDAs, and handy-terminals. The device features an internal synchronous rectifier for high efficiency; it requires no external Schottky diode. Internally fixedfrequency 1.5MHz operation provides easy post-filtering and allows the use of small inductors and capacitors. Shutdown mode places the device in standby, reducing supply current to under 1µA.. Other features of the AIC2309 include high efficiency, soft start, over temperature protection, and over current protection. It is available in a space-saving 12-pin DFN. TYPICAL APPLICATIONS CIRCUIT Fig. 1 Adjustable Output Voltage Step-Down DC/DC Converter Analog Integrations Corporation Si-Soft Research Center DS-2309G-01 20121008 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 AIC2309 Fig. 2 Fixed Output Voltage Step-Down DC/DC Converter 2 AIC2309 ORDERING INFORMATION PIN CO NFIGURATI ON A IC230 9-XX XX X XX P ACK ING TYP E TR: TA PE & REE L B G: BA G P ACK AGE TYP E DF: DFN-12 wit h he at sin k (3 x3 x0. 75-0.4 5mm ) G: Green Package Outpu t V olta ge: Vou t1/V out2 Def ault Ad justa ble -ZK:3 .3V /1.8V -ZE:3 .3V /1.2V -RK: 2.5V /1.8 V D FN-12 with heat s ink T OP VIEW VIN 2 1 12 EN 2 LX2 2 11 N C2 G ND 3 10 FB2 FB1 4 9 GN D N C1 5 8 LX1 EN 1 6 7 VIN1 Note : The expo sed pa d m ust be co nn ecte d with GND pin. E xa mple: A IC23 09GDFTR in Gree n P acka ge DFN-12 W ith Heat Sink Package and Tape & R eel Packin g Type A IC23 09-ZKGDFTR 3.3V /1.8 V V out Ve rsio n in Green Package DFN-12 W ith Hea t S ink P acka ge an d Ta pe & Ree l P acking T ype ABSOLUTE MAXIMUM RATINS Supply Input Volatge, VIN1, VIN2 6.0V -0.3V to VIN Pin Voltage for all other Pins -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 DFN-12L (3x3)* 20C/W Thermal Resistance Junction to Ambient DFN-12L (3x3)* 50C/W (Assume no Ambient Airflow) Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. *The package is place on a two layers PCB with 2 ounces copper and 2 square inch, connected by 8 vias. 3 AIC2309 ELECTRICAL CHARACTERISTICS (VIN=3.6V, VOUT=2.5V, unless otherwise specified. Typical values are at TA=25C) PARAMETER Input Voltage Range Reference Voltage SYMBOL CONDITIONS VIN 2.2 VREF 0.588 FB Input Current IFB VFB = 0.62V Quiesecnt Current IQ IOUT = 0mA, VFB = VREF + 5% Shutdown Supply Current ISHDN Enable High Input Voltage VEN_H Enable Low Input Voltage VEN_L Output Adjustment Range VOUT Output Voltage Accuracy MIN TYP MAX UNITS 5.5 V 0.612 V 50 nA 65 85 uA 0.1 1 uA VIN V 0.4 V VIN - ΔV V VOUT 3 % 0.6 -50 1.5 (ΔV = IOUT x PRDS(ON)) ΔVOUT VREF -3 P-Channel On-Resistance PRDS(ON) IOUT=200mA 0.28 0.39 N-Channel On-Resistance NRDS(ON) IOUT=200mA 0.25 0.39 P-Channel Current-Limit Threshold Oscillator Frequency fOSC Maximum Duty Cycle dutyMAX Thermal Shutdown Temperature TSD LX Leakage Current ILX IOUT=100mA 1.3 1.6 1.2 1.5 A 1.8 100 % 150 VLX=0V or VLX=3.6V -1 MHz °C 1 uA 4 AIC2309 TYPICAL PERFORMANCE CHARACTERISTICS Vout=1.8V Vout=3.3V VIN=5V VIN=3.3V VIN=5V VIN=2.5V Fig. 3 Efficiency vs. Input Voltage Fig. 5 Output Voltage vs. Temperature Fig. 7 Oscillator Frequency vs. Input Voltage Fig. 4 Efficiency vs. Output Current Fig. 6 Oscillator Frequency vs. Temperature Fig. 8 RDS(ON) vs. Input Voltage 5 AIC2309 TYPICAL PERFORMANCE CHARACTERISTICS (Continuous) Fig. 9 Supply Current vs. Input Voltage Fig. 15 Load Transient Response Fig. 10 Current Limit vs. Input Voltage Fig. 16 Load Transient Response Fig. 17 Load Transient Response 6 AIC2309 BLOCK DIAGRAM PIN DESCRIPTIONS Pin Number Pin Name Pin Function 1 VIN2 Power Input of Channel 2. 2 LX2 Pin for Switching of Channel 2. 3, 9, Exposed Pad (13) GND Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 4 FB1 Feedback of Channel 1. 5, 11 NC1, NC2 6 EN1 Chip Enable of Channel 1 (Active High). VEN1 ≦ VIN1. 7 VIN1 Power Input of Channel 1. 8 LX1 Pin for Switching of Channel 1. 10 FB2 Feedback of Channel 2. 12 EN2 Chip Enable of Channel 2 (Active High). VEN2 ≦ VIN2. No Connection or Connect to VIN. 7 AIC2309 APPLICATION INFORMATION Operation discharge, thereby preventing inductor current runaway. The AIC2309 is a low-noise step-down DC/DC converter The switching frequency will automatically return to its with current-mode PWM control architecture. It features designed value while short circuit condition is released. an internal synchronous rectifier, which eliminates the external Schottky diode and increases efficiency. During normal operation, the AIC2309 can regulate its output voltage through a feedback control circuit, which is composed of an error amplifier; a current comparator and several control signal generators. By comparing the Shutdown By connecting the EN pin to GND, the AIC2309 can be shut down to reduce the supply current to 0.1 A (typical). At this operation mode, the output voltage of step-down converter is equal to 0V. feedback voltage to the reference voltage of 0.6V, the 100% Duty Cycle Operation error amplifier varies its output voltage. The output voltage When the input voltage approaches the output voltage, of the error amplifier is compared with the summing signal the AIC2309 smoothly transits to 100% duty cycle of current sensing signal and slope compensation signal operation. This allows AIC2309 to regulate the output to determine the duty cycle of internal main power switch voltage until AIC2309 completely enters 100% duty cycle (P-channel MOSFET). While the main power switch is operation. In 100% duty cycle mode, the output voltage is turned on, the synchronous power switch (N-channel equal to the input voltage minus the voltage, which is the MOSFET) will be turned off through anti-short-through drop across the main power switch. block. Similarly, when the main power switch is turned off, the synchronous power switch will be turned on until the inductor current starts to reverse or the beginning of the next switching cycle. In order to achieve better efficiency The AIC2309 achieves 100% duty cycle operation by extending the turn-on time of the main power switch. If the summing signal of current sensing signal and slope compensation signal does not reach the output voltage level of and prevent overcharging the output capacitor. the error amplifier at the end of 90% switching period, the Current Limitation main power switch is continuously turned on and the oscilla- The AIC2309 provides current limit function by using an in- tor remains off until the summing signal of current sensing ternal sensing resistor. When the main power switch turns signal and slope compensation signal reaches the output on, current follows through the internal sensing resistor. And voltage level of the error amplifier. After the summing signal current amplifier senses the voltage, which crosses the re- of current sensing signal and slope compensation signal sistor, and amplifies it. While the sensed voltage gets higher reaches the output voltage level of the error amplifier, than reference voltage, the current limitation function is acti- the main power switch is turned off and the synchronous vated. While the current limitation function is activated, the power switch is turned on for a constant off time. At the end duty cycle will be reduced to limit the output power to protect of the constant off time, the next switching cycle is begun. the internal power switches. While the input voltage approaches the output voltage, the Short Circuit Protection switching frequency decreases gradually to smoothly transit While the output is shorted to ground, the switching to 100% duty cycle operation. frequency of AIC2309 will be reduced to one third of the If input voltage is very close to output voltage, the normal switching switching mode goes from pure PWM mode to 100% duty frequency ensures the inductor current has more time to cycle operation. During this transient state mentioned switching frequency. This lower 8 AIC2309 above, large output ripple voltage may appear on output For lower output voltage ripple, the use of low ESR terminal. ceramic capacitor is recommended. The tantalum capacitor can also be used well, but its ERS is larger than Components Selection that of ceramic capacitor. Inductor The inductor selection depends on the current ripple of When choosing the input and output ceramic capacitors, inductor, the input voltage and the output voltage. retain their capacitance over wider ranges of voltage and L VOUT fOSC IL V 1 OUT VIN X5R and X7R types are recommended because they 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 current ripple of inductor, a suitable inductance can be obtained from above equation. In addition, it is important to ensure the inductor saturation current exceeds the peak value of inductor current in application to prevent core saturation. The peak value of inductor current can be calculated according to the Output Voltage Programming (AIC2309 Adjustable Version Only) By connecting a resistive divider R11 and R12 (R21 and R22), the output voltage of AIC2309 step-down converter can be set. VOUT1 and VOUT2 can be calculated as: R VOUT 1 0.6 1 11 R12 R VOUT 2 0.6 1 21 R22 The resistive divider should sit as close to VFB pin as possible. following equation. IPEAK Layout Consideration VOUT V 1 OUT IOUT max 2 fOSC L VIN In order to ensure a proper operation of AIC2309, the following points should be managed comprehensively. Input Capacitor and Output Capacitor To prevent the high input voltage ripple and noise resulted from high frequency switching, the use of low ESR 1. The input capacitor and VIN should be placed as close as possible to each other to reduce the input voltage ripple and noise. ceramic capacitor for the maximum RMS current is 2. The output loop, which is consisted of the inductor, recommended. The approximated RMS current of the the internal main power switch, the internal synchro- input capacitor can be calculated according to the nous power switch and the output capacitor, should following equation. be kept as small as possible. 2 ICINRMS IOUT (MAX ) VOUT VIN VOUT 2 VIN IL2 12 3. The routes with large current should be kept short and wide. 4. Logically the large current on the converter should flow The selection of output capacitor depends on the required output voltage ripple. The output voltage ripple can be expressed as: VOUT IL ESR IL 8 fOSC COUT 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. 9 AIC2309 PHYSICAL DIMENSIONS (unit: mm) DFN 12L-3x3x0.75-0.45mm PACKAGE OUTLINE DRAWING D2 D 12 6 1 E E2 L 7 e PIN#1 S Y M B O L A3 A A b SEATING PLANE DFN 12L-3x3x0.75-0.45mm MILLIMETERS MIN. MAX. 0.70 0.80 A3 0.20 BSC b 0.18 0.30 D 2.90 3.10 D2 2.20 2.70 E 2.90 3.10 E2 1.40 1.80 0.45 BSC e L 0.30 0.50 Note : 1. DIMENSION AND TOLERANCING CONFORM TO ASME Y14.5M-1994. 2.CONTROLLING DIMENSIONS：MILLIMETER，CONVERTED INCH DIMENSION ARE NOT NECESSARILY EXACT. 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. 10