APW7143 3A, 12V, Asynchronous Buck Converter Features General Description * Wide Input Voltage from 4.3V to 14V The APW7143 is a 3A asynchronous Buck converter with * Output Current up to 3A * Adjustable Output Voltage from 0.8V to VIN an integrated 70m P-channel power MOSFET. The APW7143, designed with a current-mode control scheme, can convert wide input voltage of 4.3V to 14V to the output voltage adjustable from 0.8V to VIN to provide excellent - 2% System Accuracy * * 70m Integrated Power MOSFET output voltage regulation. For high efficiency over all load current range, the High Efficiency up to 92% Current-Mode Operation APW7143 is equipped with an automatic Skip/PWM mode operation. At light load, the IC operates in the Skip - Easy Feedback Compensation - Stable with Low ESR Output Capacitors mode, which keeps a constant minimum inductor peak current, to reduce switching losses. At heavy load, the IC - Fast Load/Line Transient Response works in PWM mode, which inductor peak current is programmed by the COMP voltage, to provide high efficiency - Automatic Skip/PWM Mode Operation * * Power-On-Reset Monitoring * Fixed 500kHz Switching Frequency in PWM mode * Built-in Digital Soft-Start * Current-Limit Protection with Frequency Foldback * Hiccup-Mode 50% Undervoltage Protection * shutdown mode, the supply current drops below 3A. This device, available in an 8-pin SOP-8 package, pro- Over-Temperature Protection vides a very compact system solution with minimal exter- * <3A Quiescent Current in Shutdown Mode nal components and PCB area. * Small SOP-8 Package * Lead Free and Green Devices Available and excellent output voltage regulation. The APW7143 is also equipped with power-on-reset, soft-start, and whole protections (undervoltage, over temperature, and current-limit) into a single package. In 100 90 (RoHS Compliant) 80 70 * OLPC, UMPC * Notebook Computer * Handheld Portable Device * Efficiency, (%) Applications 60 VIN=5V, VOUT=3.3V, L1=2.2H 50 40 30 VIN=12V, VOUT=5V, L1=6.8H 20 Step-down Converters Requiring High Efficiency 10 and 3A Output Current VIN=12V, VOUT=3.3V, L1=4.7H 0 0.001 0.01 0.1 1 10 Output Current, IOUT(A) ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and advise customers to obtain the latest version of relevant information to verify before placing orders. Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 1 www.anpec.com.tw APW7143 Ordering and Marking Information Package Code K : SOP-8 Operating Junction Temperature Range I : -40 to 85 C Handling Code TR : Tape & Reel Assembly Material L : Lead Free Device G : Halogen and Lead Free Device APW7143 Assembly Material Handling Code Temperature Range Package Code APW7143 K : APW7143 XXXXX XXXXX - Date Code Note: ANPEC lead-free products contain molding compounds/die attach materials and 100% matte tin plate termination finish; which are fully compliant with RoHS. ANPEC lead-free products meet or exceed the lead-free requirements of IPC/JEDEC J-STD-020C for MSL classification at lead-free peak reflow temperature. ANPEC defines "Green" to mean lead-free (RoHS compliant) and halogen free (Br or Cl does not exceed 900ppm by weight in homogeneous material and total of Br and Cl does not exceed 1500ppm by weight). Pin Configuration APW7143 VIN NC AGND FB 1 8 2 7 3 4 5 6 LX LX EN COMP SOP-8 Top View Pin 7 and 8 must be externally connected together. Absolute Maximum Ratings Symbol VIN VLX (Note 2) Parameter VIN Supply Voltage (VIN to AGND) LX to AGND Voltage Rating Unit -0.3 ~ 15 V > 100ns -1 ~ VIN+1 < 100ns - 5 ~ VIN+5 EN to AGND Voltage V -0.3 ~ VIN+0.3 FB, COMP to AGND Voltage V -0.3 ~ 6 Maximum Junction Temperature TSTG Storage Temperature TSDR Maximum Lead Soldering Temperature, 10 Seconds V 150 o -65 ~ 150 o 260 o C C C Note 2 : Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. Thermal Characteristics Symbol JA Parameter Value Junction-to-Ambient Thermal Resistance in Free Air Unit (Note 3) o SOP-8 C/W 80 Note 3: JA is measured with the component mounted on a high effective thermal conductivity test board in free air. Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 2 www.anpec.com.tw APW7143 Recommended Operating Conditions (Note 4) Symbol Parameter VIN Range Unit VIN Supply Voltage 4.3 ~ 14 V VOUT Converter Output Voltage 0.8 ~ VIN V IOUT Converter Output Current 0~3 A CIN Converter Input Capacitor (MLCC) 8 ~ 50 F COUT LOUT TA Converter Output Capacitor 20 ~ 1000 F Effective Series Resistance 0 ~ 60 m Converter Output Inductor 1 ~ 22 H Resistance of the Feedback Resistor connected from FB to AGND 1 ~ 20 k Ambient Temperature TJ Junction Temperature -40 ~ 85 o -40 ~ 125 o C C Note 4: Refer to the Typical Application Circuits Electrical Characteristics Refer to the typical application circuits. These specifications apply over VIN=12V, VOUT=3.3V, and TA= -40 ~ 85C, unless otherwise specified. Typical values are at TA=25C. Symbol Parameter APW7143 Test Conditions Unit Min Typ Max SUPPLY CURRENT IVIN IVIN_SD VIN Supply Current VFB = VREF +50mV, VEN=3V, LX=NC - 0.5 1.5 mA VIN Shutdown Supply Current VEN = 0V - - 3 A 3.9 4.1 4.3 V - 0.5 - V V POWER-ON-RESET (POR) VOLTAGE THRESHOLD VIN POR Voltage Threshold VIN rising VIN POR Hysteresis REFERENCE VOLTAGE VREF Reference Voltage Output Voltage Accuracy Regulated on FB pin - 0.8 - TJ = 25oC, IOUT=10mA, VIN=12V -1.0 - +1.0 IOUT=10mA~3A, VIN=4.75~14V -2.0 - +2.0 % Line Regulation VIN = 4.75V to 14V - +0.02 - %/V Load Regulation IOUT = 0.5A ~ 3A - -0.04 - %/A 450 500 550 kHz OSCILLATOR AND DUTY CYCLE FOSC TON_MIN Oscillator Frequency TJ = -40 ~ 125oC, VIN = 4.75 ~ 14V Foldback Frequency VOUT = 0V - 80 - kHz Maximum Converter's Duty - 99 - % Minimum Pulse Width of LX - 150 - ns Error Amplifier Transconductance VFB=VREF50mV - 200 - A/V Error Amplifier DC Gain - 80 - dB CURRENT-MODE PWM CONVERTER Gm Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 COMP = NC 3 www.anpec.com.tw APW7143 Electrical Characteristics (Cont.) Refer to the typical application circuits. These specifications apply over VIN=12V, VOUT=3.3V, and TA= -40 ~ 85C, unless otherwise specified. Typical values are at TA=25C. Symbol Parameter Current-Sense to COMP Voltage Transresistance P-Channel Switch Resistance APW7143 Test Conditions Unit Min Typ Max - 0.06 - VIN = 5V, TJ= 25C - 90 110 VIN = 12V, TJ= 25C - 70 90 V/A m PROTECTIONS ILIM VTH_UV TOTP P-Channel Switch Current-limit Peak Current 5.0 6.5 8.0 FB Under-Voltage Threshold VFB falling A 45 50 55 % FB Under-Voltage Debounce - 1 - s Over-Temperature Trip Point - 150 - o o Over-Temperature Hysteresis C - 40 - C 1.5 2 2.5 ms - 10 - 0.5 - - V - - 2.1 V SOFT-START, SOFTSTOP, ENABLE AND INPUT CURRENTS TSS Soft-Start LX Pull-Low Switch Resistance Switch is turned on for 2 ms (typ.) interval from the falling edge of enable signal. EN Shutdown Voltage Threshold VEN falling EN Enable Voltage Threshold P-Channel Switch Leakage Current IFB FB Pin Input Current IEN EN Pin Input Current Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 VEN = 0V, VLX = 0V VEN = 0V ~ VIN 4 - - 2 A -100 - +100 nA -100 - +100 nA www.anpec.com.tw APW7143 Typical Operating Characteristics (Refer to the application circuit 1 in the section "Typical Application Circuits", VIN=12V, VOUT=3.3V, L1=4.7H ) Output Voltage vs. Output Current 3.4 90 3.38 Output Voltage, VOUT (V) Efficiency, (%) Output Current vs. Efficiency 100 80 70 60 VIN=5V, VOUT=3.3V, L1=2.2H 50 40 VIN=12V, VOUT=5V, L1=6.8H 30 3.36 3.34 3.32 3.3 3.28 3.26 3.24 20 VIN=12V, VOUT=3.3V, L1=4.7H 10 3.22 3.2 0 0.001 0.01 0.1 1 0 10 1 2 3 Output Current, IOUT(A) Output Current, IOUT(A) Current-Limit Level (Peak Current) Output Voltage vs. Input Voltage vs. Junction Temperature 3.4 IOUT=500mA 3.38 Output Voltage, VOUT (V) Current Limit Level, ILIM(A) 7 6.5 6 5.5 5 3.36 3.34 3.32 3.3 3.28 3.26 3.24 3.22 4.5 3.2 -40 -20 0 20 40 60 80 4 100 120 140 6 o Junction Temperature, TJ ( C) VIN Input Current vs. Supply Voltage 10 12 14 Reference Voltage vs. Junction Temperature 2.0 0.816 VFB=0.85V 0.812 Reference Voltage, VREF (V) VIN Input Current, I VIN(mA) 8 Input Voltage, VIN (V) 1.5 1.0 0.5 0.0 0 2 4 6 8 10 12 0.804 0.800 0.796 0.792 0.788 0.784 -50 14 Supply Voltage, VIN (V) Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 0.808 -25 0 25 50 75 100 125 150 Junction Temperature, TJ (oC) 5 www.anpec.com.tw APW7143 Typical Operating Characteristics (Cont.) (Refer to the application circuit 1 in the section "Typical Application Circuits", VIN=12V, VOUT=3.3V, L1=4.7H ) Oscillator Frequency vs. Junction Temperature Oscillator Frequency, FOSC(KHz) 550 540 530 520 510 500 490 480 470 460 450 -50 -25 0 25 50 75 100 125 150 o Junction Temperature, TJ ( C) Operating Waveforms (Refer to the application circuit 1 in the section "Typical Application Circuits", VIN=12V, VOUT=3.3V, L1=4.7H ) Power On Power Off IOUT=3A IOUT=3A VIN VIN 1 1 VOUT 2 3 VOUT 2 IL1 IL1 3 CH1 : VIN , 5V/div CH2 : VOUT , 2V/div CH3 : IL1 , 2A/div Time : 5ms/div Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 CH1 : VIN , 5V/div CH2 : VOUT , 2V/div CH3 : IL1 , 2A/div Time : 10ms/div 6 www.anpec.com.tw APW7143 Operating Waveforms (Cont.) (Refer to the application circuit 1 in the section "Typical Application Circuits", VIN=12V, VOUT=3.3V, L1=4.7H ) Shutdown Enable IOUT=3A IOUT=3A VEN VEN 1 2 1 VOUT VOUT 2 IL1 IL1 3 3 CH1 : VEN , 5V/div CH2 : VOUT , 2V/div CH3 : IL1 , 2A/div Time : 1ms/div CH1 : VEN , 5V/div CH2 : VOUT , 2V/div CH3 : IL1, 2A/div Time : 100s/div Over Current Short Circuit VOUT is shorted to ground by a short wire IOUT =3~7A VLx VLX 1 1 VOUT VOUT 2 2 IL1 IL1 3 3 CH1 : VLX , 10V/div CH2 : VOUT , 2V/div CH3 : IL1 , 5A/div Time : 20s/div Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 CH1 : VLX , 5V/div CH2 : VOUT , 200mV/div CH3 : IL1 , 5A/div Time : 5ms/div 7 www.anpec.com.tw APW7143 Operating Waveforms (Cont.) (Refer to the application circuit 1 in the section "Typical Application Circuits", VIN=12V, VOUT=3.3V, L1=4.7H ) Load Transient Response Load Transient Response IOUT= 50mA-> 3A ->50mA IOUT rising/falling time=10s VOUT 1 1 IOUT= 0.5A-> 3A ->0.5A IOUT rising/falling time=10s VOUT IL1 IL1 2 2 CH1 : VOUT , 200mV/div CH2 : IL1 , 2A/div CH1 : VOUT , 100mV/div CH2 : IL1 , 2A/div Time : 100s/div Time : 100s/div Switching Waveform IOUT=0.2A Switching Waveform VLX VLX IOUT=3A 1 1 IL1 IL1 2 2 CH1 : VLX , 5V/div CH2 : IL1 , 2A/div Time : 1s/div Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 CH1 : VLX , 5V/div CH2 : IL1 , 2A/div Time : 1s/div 8 www.anpec.com.tw APW7143 Operating Waveforms (Cont.) (Refer to the application circuit 1 in the section "Typical Application Circuits", VIN=12V, VOUT=3.3V, L1=4.7H ) Line Transient VIN= 5~12V VIN rising/falling time=20s VIN 1 VOUT 2 IL1 3 CH1 : VIN , 5V/div CH2 : VOUT , 50mV/div (Voffset=3.3V) CH3 : IL1 , 2A/div Time : 100s/div Pin Description PIN No. NAME FUNCTION 1 VIN Power Input. VIN supplies the power (4.3V to 14V) to the control circuitry, gate driver, and step-down converter switch. Connecting a ceramic bypass capacitor and a suitably large capacitor between VIN and AGND eliminates switching noise and voltage ripple on the input to the IC. 2 NC No Connection. 3 AGND 4 FB Output feedback Input. The APW7143 senses the feedback voltage via FB and regulates the voltage at 0.8V. Connecting FB with a resistor-divider from the converter's output sets the output voltage from 0.8V to VIN. 5 COMP Output of the error amplifier. Connect a series RC network from COMP to AGND to compensate the regulation control loop. In some cases, an additional capacitor from COMP to AGND is required. 6 EN Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator, drive it low to turn it off. Connect this pin to VIN if it is not used. 7, 8 LX Power Switching Output. LX is the Drain of the P-Channel power MOSFET to supply power to the output LC filter. Ground of MOSFET Gate Driver and Control Circuitry. Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 9 www.anpec.com.tw APW7143 Block Diagram VIN Current Sense Amplifier Power-OnReset Current Limit POR 50%VREF UVP Soft-Start Soft-Start / Soft-Stop and Fault Logic UG Gate Driver Inhibit FB Gate Control Gm VREF Error Amplifier LX Current Compartor COMP Slope Compensation EN Over Temperature Protection Enable 1.5V FB Oscillator 500kHz AGND Typical Application Circuits 1. +12V Single Power Input Step-down Converter (with an Electrolytic Output Capacitor) C1 2.2F 2 C5 470F VIN 12V VIN L1 4.7H /3A Enable 6 8 LX EN U1 LX 7 APW7143 Shutdown 5 D1 R1 46.9K 1% COMP R3 62K C3 680pF Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 FB AGND 3 4 R2 15K 1% 10 VOUT 3.3V/3A C2 470F (ESR=30m) C4 47pF www.anpec.com.tw APW7143 Typical Application Circuits (Cont.) 2. 4.3~14V Single Power Input Step-down Converter(with ceramic Input/Output Capacitor) VIN 1 C1 VIN L1 Enable 6 8 LX LX 7 EN Shutdown VOUT U1 APW7143 5 D1 COMP R3 FB R1 1% 4 R2 1% AGND 3 C3 C2 C4 Optional a. Cost-effective Feedback Compensation (C4 is not connected) VIN(V) VOUT(V) 12 5 L1(H) 6.8 C2(F) 22 C2 ESR(m) 5 R1(k) 63.0 R2(k) 12 R3(k) 10.0 C3(pF) 1500 12 5 6.8 44 3 63.0 12 20.0 1500 12 3.3 4.7 22 5 46.9 15 10.0 1500 12 3.3 4.7 44 3 46.9 15 22.0 1500 12 2 3.3 22 5 30.0 20 10.0 1500 12 2 3.3 44 3 30.0 20 20.0 1500 12 1.2 2.2 22 5 7.5 15 8.2 1800 12 1.2 2.2 44 3 7.5 15 16.0 1800 5 3.3 2.2 22 5 46.9 15 8.2 680 5 3.3 2.2 44 3 46.9 15 20.0 680 5 1.2 2.2 22 5 7.5 15 3.0 1800 5 1.2 2.2 44 3 7.5 15 7.5 1800 C4(pF) R3(k) C3(pF) b. Fast-Transient-Response Feedback Compensation (C4 is connected) VIN(V) VOUT(V) L1(H) C2(F) C2 ESR(m) R1(k) R2(k) 12 5 6.8 22 5 63.0 12 47 33.0 470 12 5 6.8 44 3 63.0 12 47 68.0 470 12 3.3 4.7 22 5 46.9 15 47 22.0 680 12 3.3 4.7 44 3 46.9 15 47 47.0 680 12 2 3.3 22 5 30.0 20 47 13.0 1200 12 2 3.3 44 3 30.0 20 47 27.0 1200 12 1.2 2.2 22 5 7.5 15 150 7.5 2200 12 1.2 2.2 44 3 7.5 15 150 15.0 2200 5 3.3 2.2 22 5 46.9 15 56 20.0 220 5 3.3 2.2 44 3 46.9 15 56 43.0 220 5 1.2 2.2 22 5 7.5 15 330 3.3 1800 5 1.2 2.2 44 3 7.5 15 330 8.2 1500 Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 11 www.anpec.com.tw APW7143 Function Description VIN Power-On-Reset (POR) mal overload conditions, increasing lifetime of the APW7143. The APW7143 keeps monitoring the voltage on VIN pin to prevent wrong logic operations which may occur when VIN voltage is not high enough for the internal control Enable/Shutdown Driving EN to ground places the APW7143 in shutdown. When in shutdown, the internal P-Channel power MOSFET circuitry to operate. The VIN POR has a rising threshold of 4.1V (typical) with 0.5V of hysteresis. turns off, all internal circuitry shuts down and the quiescent supply current reduces to less than 3A. During start-up, the VIN voltage must exceed the enable voltage threshold. Then the IC starts a start-up process and ramps up the output voltage to the voltage target. Current-Limit Protection Digital Soft-Start The APW7143 monitors the output current, flows through the P-Channel power MOSFET, and limits the current peak The APW7143 has a built-in digital soft-start to control the rise rate of the output voltage and limit the input cur- at current-limit level to prevent loads and the IC from damages during overload or short-circuit conditions. rent surge during start-up. During soft-start, an internal voltage ramp (VRAMP), connected to one of the positive Frequency Foldback inputs of the error amplifier, rises up from 0V to 0.95V to replace the reference voltage (0.8V) until the voltage ramp The foldback frequency is controlled by the FB voltage. When the output is shorted to ground, the frequency of the oscillator will be reduced to about 80kHz. This lower reaches the reference voltage. Output Undervoltage Protection (UVP) frequency allows the inductor current to discharge safely and thereby prevent current runaway. The oscillator's fre- In the process of operation, if a short-circuit occurs, the output voltage will drop quickly. Before the current-limit quency will gradually increase to its designed rate when circuit responds, the output voltage will fall out of the re- the feedback voltage on FB again approaches 0.8V. quired regulation range. The undervoltage continually monitors the FB voltage after soft-start is completed. If a load step is strong enough to pull the output voltage lower than the undervoltage threshold, the IC shuts down converter's output. The undervoltage threshold is 50% of the nominal output voltage. The undervoltage comparator has a built-in 2s noise filter to prevent the chips from wrong UVP shutdown caused by noise. The undervoltage protection works in a hiccup mode without latched shutdown. The IC will initiate a new soft-start process at the end of the preceding delay. Over-Temperature Protection (OTP) The over-temperature circuit limits the junction temperature of the APW7143. When the junction temperature exceeds TJ = +150C, a thermal sensor turns off the power MOSFET, allowing the devices to cool. The thermal sensor allows the converters to start a start-up process and regulate the output voltage again after the junction temperature cools by 40C. The OTP is designed with a 40oC hysteresis to lower the average TJ during continuous therCopyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 12 www.anpec.com.tw APW7143 Application Information T=1/FOSC Setting Output Voltage The regulated output voltage is determined by: VOUT = 0.8 (1 + VLX R1 ) R2 DT (V) I IOUT Suggested R2 is in the range from 1K to 20k. For portable applications, a 10k resistor is suggested for R2. To prevent stray pickup, locate resistors R1 and R2 close to APW7143. IL IOUT IQ1 I Input Capacitor Selection ICOUT Each time, when the P-channel power MOSFET (Q1) turns on, small ceramic capacitors for high frequency decoupling and bulk capacitors are required to supply the surge current. The small ceramic capacitors have to be placed physically close to the VIN and between the VIN and the anode of the Schottky diode (D1). VOUT Figure 1 Converter Waveforms Output Capacitor Selection The important parameters for the bulk input capacitor are the voltage rating and the RMS current rating. For reliable operation, select the bulk capacitor with voltage and current ratings above the maximum input voltage and largest RMS current required by the circuit. The capacitor voltage rating should be at least 1.25 times greater than the maximum input voltage and a voltage rating of 1.5 times is a conservative guideline. The RMS current (IRMS) of the bulk input capacitor is calculated as the following equation: IRMS = IOUT D (1- D) VOUT (A) where D is the duty cycle of the power MOSFET. An output capacitor is required to filter the output and supply the load transient current. The filtering requirements are the functions of the switching frequency and the ripple current (I). The output ripple is the sum of the voltages, having phase shift, across the ESR and the ideal output capacitor. The peak-to-peak voltage of the ESR is calculated as the following equations: D= VOUT + VD VIN + VD ........... (1) I = VOUT *(1 - D) FOSC *L ........... (2) VESR = I *ESR For a through hole design, several electrolytic capacitors may be needed. For surface mount designs, solid tantalum capacitors can be used, but caution must be exercised with regard to the capacitor surge current where VD is the forward voltage drop of the diode. The peak-to-peak voltage of the ideal output capacitor is calculated as the following equation: rating. VCOUT = VIN VIN IQ1 Q1 IL VOUT ICOUT ........... (4) Therefore, the AC peak-to-peak output voltage (VOUT ) is shown below: IOUT L D1 I (V) 8 FOSC COUT For the applications, using bulk capacitors, the VCOUT is much smaller than the V ESR and can be ignored. CIN LX ........... (3) (V) ESR VOUT = I ESR (V) ........... (5) COUT Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 13 www.anpec.com.tw APW7143 Application Information (Cont.) Output Capacitor Selection (Cont.) VOUT *(VIN - VOUT) 1.2 500000 *L *VIN For the applications, using ceramic capacitors, the VESR is much smaller than the V COUT and can be ignored. L Therefore, the AC peak-to-peak output voltage (VOUT ) is close to VCOUT . VOUT *(VIN - VOUT ) 600000 *VIN (H) ........... (6) where VIN = VIN(MAX) The load transient requirements are the functions of the Output Diode Selection slew rate (di/dt) and the magnitude of the transient load current. These requirements generally met with a mix of The Schottky diode carries load current during the off-time. The average diode current is therefore dependent on the capacitors and careful layout. High frequency capacitors initially supply the transient and slow the current P-channel power MOSFET duty cycle. At high input voltages the diode conducts most of the time. As VIN approaches load rate seen by the bulk capacitors. The bulk filter capacitor values are generally determined by the ESR VOUT, the diode conducts only a small fraction of the time. The most stressful condition for the diode is when the (Effective Series Resistance) and voltage rating requirements rather than actual capacitance requirements. output is short-circuited. Therefore, it is important to adequately specify the diode peak current and average High frequency decoupling capacitors should be placed physically as close to the power pins of the load as power dissipation so as not to exceed the diode ratings. possible. Be careful not to add inductance in the circuit board wiring that could cancel the usefulness of these Under normal load conditions, the average current conducted by the diode is: low inductance components. An aluminum electrolytic capacitor's ESR value is related to the case size with lower ID = ESR available in larger case sizes. However, the VIN - VOUT IOUT VIN + VD The APW7143 is equipped with whole protections to Equivalent Series Inductance (ESL) of these capacitors increases with case size and can reduce the usefulness reduce the power dissipation during short-circuit condition. Therefore, the maximum power dissipation of of the capacitor to high slew-rate transient loading. the diode is calculated from the maximum output current as: Inductor Value Calculation The operating frequency and inductor selection are PDIODE(MAX) = VD *ID(MAX) interrelated in that higher operating frequencies permit the use of a smaller inductor for the same amount of where IOUT = IOUT(MAX) inductor ripple current. However, this is at the expense of efficiency due to an increase in MOSFET gate charge Remember to keep leading length short and observing proper grounding to avoid ringing and increasing dissipation. losses. The equation (2) shows that the inductance value has a direct effect on ripple current. Accepting larger values of ripple current allows the use of low inductances, but results in higher output voltage ripple and greater core losses. A reasonable starting point for setting ripple current is I 0.4 IOUT(MAX) . Remember, the maximum ripple current occurs at the maximum input voltage. The minimum inductance of the inductor is calculated as the following equation: Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 14 www.anpec.com.tw APW7143 Layout Consideration In high power switching regulator, a correct layout is important to ensure proper operation of the regulator. In 4. Place the decoupling ceramic capacitor C1 near the VIN as close as possible. The bulk capacitors C5 are also placed near VIN. Use a wide power ground plane general, interconnecting impedance should be minimized by using short, wide printed circuit traces. Signal and to connect the C1, C2, C5, and Schottky diode to provide a low impedance path between the com- power grounds are to be kept separate and finally combined using ground plane construction or single ponents for large and high slew rate current. point grounding. Figure 2 illustrates the layout, with bold lines indicating high current paths. Components along C2 D1 the bold lines should be placed close together. Below is a checklist for your layout: C1 VIN 1. Begin the layout by placing the power components 1 first. Orient the power circuitry to achieve a clean power flow path. If possible, make all the connections on Ground 4 8 SOP-8 2 3 7 6 VLX VOUT L1 5 APW7143 one side of the PCB with wide, copper filled areas. Ground 2. In Figure 2, the loops with same color bold lines conduct high slew rate current. These interconnecting Figure 3 Recommended Layout Diagram impedances should be minimized by using wide and short printed circuit traces. 3. Keep the sensitive small signal nodes (FB, COMP) away from switching nodes (LX or others) on the PCB. Therefore, place the feedback divider and the feedback compensation network close to the IC to avoid switching noise. Connect the ground of feedback divider directly to the AGND pin of the IC using a dedicated ground trace. + VIN - 1 VIN 6 Compensat ion Network C1 L1 LX 8 LX 7 EN + D1 U1 APW7143 C2 Load V OUT - 5 COMP C3 R1 FB 4 R3 AGND 3 R2 (Optional) Feedback Divider Figure 2 Current Path Diagram Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 15 www.anpec.com.tw APW7143 Package Information SOP-8 D E E1 SEE VIEW A h X 45 c A 0.25 b GAUGE PLANE SEATING PLANE A1 A2 e L VIEW A S Y M B O L SOP-8 MILLIMETERS MIN. INCHES MAX. A MIN. MAX. 1.75 0.069 0.004 0.25 0.010 A1 0.10 A2 1.25 b 0.31 0.51 0.012 0.020 c 0.17 0.25 0.007 0.010 D 4.80 5.00 0.189 0.197 E 5.80 6.20 0.228 0.244 E1 3.80 4.00 0.150 0.157 e 0.049 1.27 BSC 0.050 BSC h 0.25 0.50 0.010 0.020 L 0.40 1.27 0.016 0.050 0 0 8 0 8 Note: 1. Follow JEDEC MS-012 AA. 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. Inter-lead flash and protrusions shall not exceed 10 mil per side. Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 16 www.anpec.com.tw APW7143 Carrier Tape & Reel Dimensions P0 P2 P1 A B0 W F E1 OD0 K0 A0 A OD1 B B T SECTION A-A SECTION B-B H A d T1 Application A H 330.02.00 50 MIN. SOP-8(P) T1 C d D 12.4+2.00 13.0+0.50 1.5 MIN. -0.00 -0.20 P0 P1 P2 D0 D1 4.00.10 8.00.10 2.00.05 1.5+0.10 -0.00 1.5 MIN. W E1 20.2 MIN. 12.00.30 1.750.10 T A0 B0 F 5.50.05 K0 0.6+0.00 6.400.20 5.200.20 2.100.20 -0.40 (mm) Devices Per Unit Package Type Unit Quantity SOP-8 Tape & Reel 2500 Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 17 www.anpec.com.tw APW7143 Reflow Condition (IR/Convection or VPR Reflow) tp TP Critical Zone TL to TP Temperature Ramp-up TL tL Tsmax Tsmin Ramp-down ts Preheat t 25C to Peak 25 Time Reliability Test Program Test item SOLDERABILITY HOLT PCT TST ESD Latch-Up Method MIL-STD-883D-2003 MIL-STD-883D-1005.7 JESD-22-B, A102 MIL-STD-883D-1011.9 MIL-STD-883D-3015.7 JESD 78 Description 245C, 5 sec 1000 Hrs Bias @125C 168 Hrs, 100%RH, 121C -65C~150C, 200 Cycles VHBM > 2KV, VMM > 200V 10ms, 1tr > 100mA Classification Reflow Profiles Profile Feature Average ramp-up rate (TL to TP) Preheat - Temperature Min (Tsmin) - Temperature Max (Tsmax) - Time (min to max) (ts) Time maintained above: - Temperature (TL) - Time (tL) Peak/Classification Temperature (Tp) Time within 5C of actual Peak Temperature (tp) Ramp-down Rate Sn-Pb Eutectic Assembly Pb-Free Assembly 3C/second max. 3C/second max. 100C 150C 60-120 seconds 150C 200C 60-180 seconds 183C 60-150 seconds 217C 60-150 seconds See table 1 See table 2 10-30 seconds 20-40 seconds 6C/second max. 6C/second max. 6 minutes max. 8 minutes max. Time 25C to Peak Temperature Notes: All temperatures refer to topside of the package. Measured on the body surface. Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 18 www.anpec.com.tw APW7143 Classification Reflow Profiles (Cont.) Table 1. SnPb Eutectic Process - Package Peak Reflow Temperatures 3 Package Thickness Volume mm <350 <2.5 mm 240 +0/-5C 2.5 mm 225 +0/-5C 3 Volume mm 350 225 +0/-5C 225 +0/-5C Table 2. Pb-free Process - Package Classification Reflow Temperatures 3 3 3 Package Thickness Volume mm Volume mm Volume mm <350 350-2000 >2000 <1.6 mm 260 +0C* 260 +0C* 260 +0C* 1.6 mm - 2.5 mm 260 +0C* 250 +0C* 245 +0C* 2.5 mm 250 +0C* 245 +0C* 245 +0C* *Tolerance: The device manufacturer/supplier shall assure process compatibility up to and including the stated classification temperature (this means Peak reflow temperature +0C. For example 260C+0C) at the rated MSL level. Customer Service Anpec Electronics Corp. Head Office : No.6, Dusing 1st Road, SBIP, Hsin-Chu, Taiwan Tel : 886-3-5642000 Fax : 886-3-5642050 Taipei Branch : 2F, No. 11, Lane 218, Sec 2 Jhongsing Rd., Sindian City, Taipei County 23146, Taiwan Tel : 886-2-2910-3838 Fax : 886-2-2917-3838 Copyright ANPEC Electronics Corp. Rev. A.1 - Apr., 2008 19 www.anpec.com.tw