AIC2566 23V 3A Step-Down DC/DC Converter FEATURES DESCRIPTION 3A Continuous Output Current The AIC2566 is a high efficiency, step-down Programmable Soft Start DC/DC converter that builds in a high side 100mΩ Internal Power MOSFET Switch power MOSFET. It offers continuous 3A output Stable with Low ESR Output Ceramic Capacitors current over a very wide input voltage range Up to 95% Efficiency with excellent load and line regulation. 22µA Supply Current in Shutdown Mode Well-performed current mode operation makes Fixed 385KHz Frequency fast transient response and feedback loop Thermal Shutdown stabilization easier. Cycle by Cycle Over Current Protection The AIC2566 draws only 22A supply current in Wide 4.75 to 23V Operating Input Range shutdown mode. Current limit and thermal Output Adjustable from 0.92V to 16V Under Voltage Lockout shutdown function are also provided to prevent damage. The AIC2566 is available in an 8-pin SOP exposed pad package. APPLICATIONS Networking Products such as DSL Modems Distributed Power Systems Battery Charger Pre-Regulator for Linear Regulators TYPICAL APPLICATIONS CIRCUIT * Note: C7 is needed for high ESR output capacitor Analog Integrations Corporation Si-Soft Research Center DS-2566G-02 20110125 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 AIC2566 ORDERING INFORMATION AIC2566XXX XX PIN CONFIGURATION PACKING T YPE TR: TAPE & REEL TB: TUBE SOP-8 Exposed Pad (Heat Sink ) TOP VIEW BS 1 PACKAGING TYPE R8: SOP-8 Exposed Pad (Heat Sink) G/W: GREEN PACKAGE IN 2 SW 3 GND 4 8 SS 7 EN 6 COMP 5 FB Note: The exposed pad must be connected wit h GND pin. Example: AIC2566GR8TR GREEN SOP-8 Exposed Pad(Heat Sink) Package and TAPE & REEL Packing Type ABSOLUTE MAXIMUM RATINGS Input Voltage (VIN) ............................................................................................................................. 24V SW pin Voltage (VSW) ........................................................................................................................ 25V BS Pin Voltage ............................................................................................................................VSW+6V All Other Pins Voltage ........................................................................................................... -0.3V to 6V Operating Ambient Temperature Range TA .......................................................................... -40ºC~85ºC Operating Maximum Junction Temperature TJ .............................................................................. 150ºC Storage Temperature Range TSTG ...................................................................................... -65ºC~150ºC Lead Temperature (Soldering 10 Sec.) ......................................................................................... 260ºC Thermal Resistance Junction to Case SOP-8 Exposed Pad* ............................................15C/W Thermal Resistance Junction to Ambient SOP-8 Exposed Pad* ............................................60C/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. 2 AIC2566 ELECTRICAL CHARACTERISTICS (VIN=12V, unless otherwise specified. Typical values are at TA=+25C) (Note1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Shutdown Supply Current VEN = 0V 22 36 A Supply Current VEN ≥ 3V, VFB=1V 0.6 1.3 mA 0.92 0.938 V 4.75V ≤ VIN ≤ 23V Feedback Voltage VFB Error Amplifier Voltage Gain AVEA Error Amplifier Transconductance GEA High-Side Switch On-Resistance RDS(ON)1 100 m Low-Side Switch On-Resistance RDS(ON)2 10 High-Side Switch Leakage Current 400 ΔICOMP = 10A Oscillation Frequency GCS fs 335 V/V 1120 10 A/V A 5.0 A 3.8 A/V 385 435 KHz VFB= 0V 120 KHz 90 % Maximum Duty Cycle DMAX VFB= 0.8V Minimum Duty Cycle DMIN VFB = 1.1V Shutdown Threshold 1.1 Enable Pull Up Current VEN = 0V Under Voltage Lockout Threshold VIN Rising Under Voltage Lockout Threshold Hysteresis Thermal Shutdown 800 0 3.6 Short Circuit Oscillation Frequency Soft Start Period 500 VEN = 0V, VSW = 0V Current Limit Current Sense to COMP Transconductance 0.902 Css = 0.1 uF 3.6 0 % 1.5 2.0 V 1.0 2.5 A 4.0 4.4 V 210 mV 10 ms 160 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). 3 AIC2566 TYPICAL PERFORMANCE CHARACTERISTICS 100 95 EFFICIENCY (%) 90 VIN=7.0V VIN=12V 85 VIN=23V 80 75 70 65 60 0.0 VOUT=5.0V 0.5 1.0 1.5 2.0 2.5 3.0 OUTPUT CURRENT (A) Fig. 1 Efficiency vs. Load Current Fig. 3 Switching Frequency vs. Input Voltage Fig. 5 Supply Current vs. Input Voltage Fig. 2 Efficiency vs. Load Current Fig. 4 Switching Frequency vs. Temperature Fig. 6 Supply Current vs. Temperature 4 AIC2566 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 7 VREF vs. Temperature Fig. 9 Output Ripple Voltage Fig. 11 Startup Fig. 8 Output Ripple Voltage Fig. 10 Startup Fig. 12 Startup 5 AIC2566 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 13 Startup Fig. 14 Load Transient Response Fig. 15 Load Transient Response 6 AIC2566 BLOCK DIAGRAM 120 / 385KHz 0.1Ω Functional Block Diagram of AIC2566 7 AIC2566 PIN DESCRIPTIONS PIN1: BS: High Side Gate Drive Boost Input. BS voltage to regulate that voltage. Drive supplies the drive for the high-side feedback with a resistive voltage divider N-Channel MOSFET switch. Connect a from the output voltage. 10nF or greater capacitor from SW to BS to power the high-side switch. PIN6: COMP: Compensation Node. COMP is used to compensate the regulation control loop. PIN2: IN: Power Input. IN supplies the power to Connect a series RC network form the IC, as well as the step-down COMP to GND to compensate the converter switches. Drive IN with a 4.75 regulation control loop. In some cases, to 23V power source. By pass IN to an additional capacitor from COMP to GND with a suitable large capacitor to GND is required. eliminate noise on the input to the IC. PIN 7: EN: PIN3: SW: Enable Input. EN is a digital input that Power Switching Output. SW is the turns the regulator on or off. Drive EN switching node that supplies power to high to turn on the regulator. Drive it low the output. Connect the output LC filter to turn it off. For automatic start-up, from switch to the output load. Note that leave EN unconnected. a capacitor is required from SW to BS to power the high-side switch. PIN 8: SS: Soft Star Control Input. SS controls the soft star period. Connect a capacitor PIN4: GND: Ground. from SS to GND to set the soft-star period. To disable the soft-star feature, PIN5: FB: Feedback Input. FB senses the output leave the SS pin unconnected. 8 AIC2566 COMPONENT SELECTION VIN (V) VOUT (V) 12 1.8 12 2.5 12 3.3 12 5.0 L1 (H) 6.8 (COOPER BUSSMANN DR125-6R8-R) 10 (COOPER BUSSMANN DR1050-100-R) 15 (COOPER BUSSMANN DRQ125-150-R) 15 (COOPER BUSSMANN DRQ125-150-R) C3 (F) R3 (k) C6 (nF) 22 ceramic (Taiyo Yuden EMK325BJ226MM-T) 2.2 8.2 9.53 10 22 ceramic (Taiyo Yuden EMK325BJ226MM-T) 3.0 6.8 16.9 10 22 ceramic (Taiyo Yuden EMK325BJ226MM-T) 5.6 3.9 25.8 10 22 ceramic (Taiyo Yuden EMK325BJ226MM-T) 6.2 3.3 44.2 10 R1 (k) R2 (k) APPLICATION INFORMATION resistor, and amplifies it. While the sensed voltage Operation The AIC2566 is a fixed-frequency and high gets higher than reference voltage, the current efficiency converter with limitation function is activated. While the current architecture. By limitation function is activated, the duty cycle will selecting appropriate circuit components, it can be reduced to limit the output power to protect the achieve fast transient response. During normal internal power switches. step-down current-mode PWM DC/DC control operation, the AIC2566 can regulate its output Short Circuit Protection voltage through a feedback control circuit, which is While the output is shorted to ground, the composed current switching frequency of AIC2566 will be reduced to comparator and several control signal generators. one third of the normal switching frequency. This By comparing the feedback voltage to the lower switching frequency ensures the inductor reference voltage of 0.92V, the error amplifier current has more time to discharge, thereby varies the voltage at COMP pin. The voltage at preventing COMP pin is compared with the summing signal of switching frequency will automatically return to its current sensing signal and slope compensation designed value while short circuit condition is signal to determine the duty cycle of internal power released. of an error amplifier; a switch. Current Limitation inductor current runaway. The Soft-Start The AIC2566 provides the soft-start function. The AIC2566 provides current limit function by Initially, the voltage at SS pin is 0V. Then an using an internal sensing resistor. When the internal current source of 6A (typ.) charges an internal power switch turns on, current follows external soft-start capacitor. During the soft-start through the internal sensing resistor. And current period, the voltage at SS pin will limit the feedback amplifier senses the voltage, which crosses the threshold voltage at FB pin. When the voltage at 9 AIC2566 SS pin is higher than 0.92V, the feedback Diode threshold voltage at FB pin reaches the desired A Schottky diode with low forward drop voltage value. The soft-start time can be calculated in and fast reverse recovery is the ideal choice for accordance with the following equation. better efficiency. The forward drop voltage of a t SS C 5 Schottky diode will result in the conduction losses 0.92V 6A in the diode, and the diode capacitance (CT or CD) The soft-start capacitor is discharged to GND will cause the switching losses. Therefore, it is when the EN pin is connected to GND. necessary to consider both forward voltage drop Shutdown and diode capacitance for diode selection. In By connecting the EN pin to GND, the AIC2566 addition, the rating of selected Schottky diode can be shut down to reduce the supply current to should be able to handle the input voltage and the 22A (typ.). At this operation mode, the output maximum peak diode current. voltage of step-down converter is equal to 0V. For Input Capacitor and Output Capacitor automatic startup, leave EN pin unconnected. To prevent the high input voltage ripple and noise Components Selection resulted from high frequency switching, the use of Inductor low ESR ceramic capacitor for the maximum RMS The inductor selection depends on the current current is recommended. The approximated RMS ripple of inductor, the input voltage and the output current of the input capacitor can be calculated voltage. according to the following equation. L VOUT f S I L V 1 OUT VIN 2 I CINRMS I OUT ( MAX ) VOUT VIN VOUT 2 VIN 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 I 2L 12 The selection of output capacitor depends on the required output voltage ripple. The output voltage ripple can be expressed as: acceptable current ripple of inductor, a suitable I L ESR I L 8 f S C OUT inductance can be obtained from above equation. VOUT In addition, it is important to ensure the inductor For lower output voltage ripple, the use of low saturation current exceeds the peak value of ESR ceramic capacitor is recommended. inductor current in application to prevent core saturation. The peak value of inductor current can be calculated according to the following equation. I PEAK VOUT V 1 OUT I OUT max 2 fS L VIN When choosing the input and output ceramic capacitors, recommended X5R and X7R because they types retain are their capacitance over wider ranges of voltage and temperature than other types. 10 AIC2566 Soft-Start Capacitor The soft-start of AIC2566 begins from VSS=0V and ends while VSS reaches 0.92V. During the soft-start period, an internal current source of 6A (typ.) different conversions and output capacitors are requires, some values of the compensation components may need to be adjusted to ensure stability. charges the soft-start capacitor. Hence, the Layout Consideration soft-start capacitor should be large enough to In order to ensure a proper operation of AIC2566, ensure that the output voltage has reached the the regulation value before the soft-start function has comprehensively. finished. 1. Output Voltage Programming 2. The input capacitor and VIN should be The output loop, which is consisted of the 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. In order to avoid the poor output voltage ripple and low efficiency caused by instability, AIC2566 managed Schottky diode and the output capacitor, as possible. Loop Compensation be inductor, the internal power switch, the R 0.92 1 1 R2 The resistive divider should sit as close to FB pin should reduce the input voltage ripple and noise. can be set. VOUT can be calculated as: VOUT points placed as close as possible to each other to By connecting a resistive divider R1 and R2, the output voltage of AIC2566 step-down converter following 5. In order to prevent the effect from noise, the IC’s GND pin should be placed close to the requires a proper external compensation network to compensate its feedback loop. In this external ground of the input bypass capacitor and compensation network, the compensation resistor, should be away from the ground of the R3, and the compensation capacitor, C6, are used Schottky diode. to set the high-frequency integrator gain and the 6. The FB pin should be connected to the integrator zero. C7 is used to cancel the zero feedback resistors directly and the route caused by the output capacitor and its ESR. While should be away from the noise sources. using the ceramic capacitor as the output capacitor, Fig. 16 to 19 shows the layout diagrams of C7 can be omitted due to the small ESR. AIC2566. The values of the compensation components given in this data sheet yield a stable control loop for the given output voltage and capacitor. If 11 AIC2566 Fig. 16 Top Layer Fig. 17 Bottom Layer Fig. 18 Top Over Layer Fig. 19 Bottom Over Layer 12 AIC2566 PHYSICAL DIMENSIONS (unit: mm) • SOP-8 Exposed Pad (Heat Sink) D D1 EXPOSED THERMAL PAD(Heat Sink) (BOTTOM CENTER OF PACKAGE) h X 45° A A SEE VIEW B A e H E E1 S Y M B O L WITH PLATING 0.25 C A1 B GAUGE PLANE SEATING PLANE L VIEW B BASE METAL SECTION A-A Note : 1. Refer to JEDEC MS-012E. 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. SOP-8 Exposed Pad(Heat Sink) MILLIMETERS MIN. MAX. A 1.35 1.75 A1 0.00 0.15 B 0.31 0.51 C 0.17 0.25 D 4.80 5.00 D1 1.50 3.50 E 3.80 4.00 E1 1.0 2.55 e 1.27 BSC H 5.80 h 0.25 0.50 L 0.40 1.27 θ 0° 8° 6.20 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. 13