APW1173 2A SWITCH STEP DOWN SWITCHING REGULATOR Features General Description • • • • The APW 1173 is a step down monolithic power switching regulator with a switching current limit of 3.8A so it is able to deliver more than 2A DC current to the load depending on the application conditions. The output voltage can be set from 1.235V to 22V.The high current level is also achieved utilize an SO8 package with exposed pad frame. The type of package allows to re-duce the Rth (j-amb) down to approximately 45°C/W. An internal oscillator fixes the switching frequency at 500KHz. Having a minimum input voltage of 4.8V only, it is particularly suitable for 5V bus, available in all computer related applications. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short. circuit protection. 2A Internal Switch Operating Input Voltage from 4.8V to 22V 3.3V ±2% Reference Voltage Output Voltage : APW1173 - adjustable from 1.235V to 20V • • • • • • • • • • • • Low Dropout Operation: 100% Duty Cycle 500KHz Internally Fixed Frequency Voltage Feed-Forward Zero Load Current Operation Internal Current Limit Inhibit for Zero Current Consumption Synchronization Protection Against Feedback Disconnection Thermal Protection External Soft-Start Pin Description Over-Voltage Protection Lead Free Available (RoHS Compliant) Applications • Consumer: STB, DVD, TV, VCR, Car Radio, LCD monitors • • Networking: XDSL, Modems, DC-DC Modules OUT 1 8 VCC SYNC 2 7 GND INH 3 6 VREF COMP 4 5 FB SOP-8-P (Top View) Computer: Printers, Audio/Graphic Cards, Optical Storage, Hard Disk Drive • = Thermal Pad (connected to GND plane for better heat dissipation) Industrial: Chargers, Car Battery DC-DC Converters 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.5 - Aug., 2005 1 www.anpec.com.tw APW1173 Ordering and Marking Information Package Code KA : SOP-8-P Operating Ambient Temp. Range C : 0 to 70 °C I : -40 to 85 °C Handling Code TU : Tube TR : Tape & Reel Lead Free Code L : Lead Free Device Blank : Orginal Device APW1173 Lead Free Code Handling Code Temp. Range Package Code APW1173 XXXXX APW1173 KA : 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 and compatible with both SnPb and lead-free soldiering operations. 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. Block Diagram VREF VC C VREF Buffer Voltages Monitor Thermal Protection COMP Peak to Peak C urrent Limit FB E/A Driver PWM V REF =1.235V D OVP Q Ck Oscillator 1.25V REF Frequency Shifter SYNC OUT Inhibit GND INH Absolute Maximum Ratings Symbol VCC VOUT Parameter Input voltage (VCC to GND) Output DC voltage Value Unit 25 -1 to 25 V V -0.7 ~ VCC V VIO COMP and FB to GND IOUT Output current 0 to current limit A VREF VREF to GND 3.3 V PD Average Power Dissipation, TA < 50° 2.2 W TJ Junction Temperature 150 °C TSTG Storage Temperature -65 ~ 150 °C TSDR Soldering Temperature, 10 seconds 300 °C VESD Minimum ESD rating (Human body mode) ±3 KV Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 2 www.anpec.com.tw APW1173 Pin Function Description No. PIN Description 1 OUT 2 SYNC 3 INH 4 COMP 5 FB 6 VREF 3.3V reference voltage output, no Capacitor Is requested for stability. 7 GND Ground. 8 VCC Unregulated DC input voltage. Regulator Output. Master/Slave synchonization. A logical signal (active high) disables the device. If INH not used the pin must be connected to GND. When it is open an internal pull-up disable the device. E/A output for frequency compensation. Feedback input. Connecting directly to this pin results in an output voltage of 1.235V(APW1173). An external resistive divider is required for higher output voltages. Thermal Characteristics Parameter Symbol θJA Junction to ambient thermal resistance in free air Value Unit 45.7 °C/W * The area of the thermal pad is 4.5mm X 2mm and the GND plane is 60mm X 60mm. Connect the thermal pad and the GND plane by 8 vias. TA = 25°C. Electrical Characteristics The * denotes the specifications that apply over TA = -40 ~ 85oC. Typical values are at TA = 25oC. VCC = 12V unless otherwise specified. Symbol VCC V UVLO Parameter APW1173 Test condition Min Operating input voltage range V O = 1.235V; IO = 2A * 4.7 UVLO threshold voltage * 3.8 V CC rising Hysteresis Dropout voltage V CC = 4.8V; IO = 2A * ILIM Maximum limiting current V CC = 4.8V to 22V * Switching frequency Main design * Duty cycle Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 4.2 Max V 4.6 V V 1.0 1.2 V 3.3 3.8 4.3 A 400 500 600 410 500 590 0 3 Unit 22 0.3 Vd fs Typ 100 KHz % www.anpec.com.tw APW1173 Electrical Characteristics (Cont.) The * denotes the specifications that apply over TA = -40 ~ 85oC. Typical values are at TA = 25oC. VCC = 12V unless otherwise specified. Symbol Parameter APW1173 Test condition Unit Min Typ Max 1.22 1.235 1.25 Dynamic Characteristics VFB η Voltage feedback APW1173 4.8V < VCC < 22V, 20mA < IO <2A Efficiency VO = 5V, VCC = 12V, IOUT = 1A * 1.198 1.235 1.272 82 V % DC Characteristics Iqop Iq Total Operating Quiescent Current Quiescent Current Iqst-by Total Stand-by Quiescent Current * Duty Cycle = 0; VFB = 1.5V 12 mA 10 mA VINH > 2.2V * 50 100 µA VCC = 22V; VINH > 2.2V * 80 150 µA Inhibit VINH INH Threshold Voltage Device ON 1.1 1.3 1.5 V Device OFF 1.2 1.4 1.6 V INH Pull-Up Current VINH < 3V 1 µA Maximum INH Voltage IINH = 0A 4.3 V 3.8 V Error Amplifier VOH High Level Output Voltage VFB = 1V VOL Low Level Output Voltage VFB = 1.5V IO source Source Output Current IO sink Sink Output Current IFB gm 3.5 0.4 VCOMP = 1.9V; VFB = 1V VCOMP = 1.9V; VFB = 1.5V V 200 300 µA 1 1.5 mA 4 µA Source Bias Current VFB = 1.5V 2.5 Maximum FB Voltage IFB = 0µA 2.1 V Trans-conductance VFB = 1.255V to 1.215V, ICOMP = -0.1mA to 0.1mA VCOMP = 1.9V 2.3 mA/V SYNC Function High Input Voltage VCC = 4.8 to 22V Low Input Voltage VCC = 4.8V to 22V 2.5 VREF V 0.74 V VSYNC = 0.74V 0.11 0.25 VSYNC = 2.33V 0.21 0.45 Master Output Amplitude ISOURCE = 3mA 2.75 3 V Output Pulse Width No load, VSYNC =1.65V 0.2 0.35 µs Slave Sink Current Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 4 mA www.anpec.com.tw APW1173 Electrical Characteristics (Cont.) The * denotes the specifications that apply over TA = -40 ~ 85oC. Typical values are at TA = 25oC. VCC = 12V unless otherwise specified. Symbol Parameter APW1173 Test condition Unit Min Typ Max 3.234 3.3 3.366 V 3.2 3.3 3.399 V Reference Section IREF = 0mA VREF VREF Output Voltage IREF = 0mA to 5mA,VCC = 4.4A to * 22V Line Regulation IREF = 0mA,VCC = 4.4A to 22V 5 10 mV Load Regulation IREF = 0mA to 5mA 8 15 mV 18 30 mA Short Circuit Current 10 Other Thermal Limiting Protection 160 °C Hysteresis 30 °C Over-Voltage Protection Threshold Voltage VCOMP = 0.8V * 120 125 130 % Typical Application Circuit VREF = 3.3V VOUT = 3.3V L 22uH 1 2 3 4 COUT 100uF RC1 4.3K D1 1N5819 D2 1N4148 CC2 220pF Rev. A.5 - Aug., 2005 VCC SYNC GND INH VREF COMP FB 8 7 6 5 APW1173 R1 C1 137K 1uF CC1 2.2nF Copyright ANPEC Electronics Corp. OUT RF2 3.3K RF1 5.6K CIN VIN 22uF 4.8V to 22V Soft Start Circuit 5 www.anpec.com.tw APW1173 Other Application Circuits Dual output voltage application VOUT2 = 5V N1/N2=2 VOUT1 = 3.3V 1N4148 VREF = 3.3V L 22uH RF1 5.6K 1 OUT VCC 8 2 SYNC GND 7 3 INH 4 COUT2 47uF RF2 3.3K COUT1 100uF COMP FB 6 5 APW1173 RC1 4.3K D1 1N5819 VREF CIN 22uF CC1 2.2nF VIN=5V CC2 220pF BuckBoost regulator VREF = 3.3V VOUT = -12V L 15uH 1 OUT 2 D1 1N5819 RF2 24K RF1 2.7K COUT 100uF Rev. A.5 - Aug., 2005 INH 4 COMP RC1 4.3K CC1 2.2nF Copyright ANPEC Electronics Corp. SYNC 3 VCC GND VREF FB 8 7 6 5 APW1173 CIN2 CIN1 22uF25V 22uF VIN=5V CC2 220pF 6 www.anpec.com.tw APW1173 Typical Operating Characteristics Line regulation of VREF Load regulation of VREF 12 0 -2 Load regulation (mV) Line regulation (mV) 10 8 6 4 -4 -6 -8 -10 -12 2 -14 0 -16 -50 -25 0 25 50 75 100 125 -50 Junction Temperature (o C) -25 0 25 50 75 100 125 100 125 Junction Temperature (o C) Short circuit current of VREF VREF 3.40 0 3.38 -2 3.34 -6 3.32 VREF (V) Short circuit current (mA) 3.36 -4 -8 -10 3.30 3.28 3.26 -12 3.24 -14 3.22 -16 3.20 -50 -25 0 25 50 75 100 125 -50 Junction Temperature (o C) Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 -25 0 25 50 75 Junction Temperature (o C) 7 www.anpec.com.tw APW1173 Typical Operating Characteristics (Cont.) Source ability of EA Sink ability of EA 0.0 300 -0.5 Sink current (mA) Source current (uA) 250 200 150 100 -1.0 -1.5 -2.0 50 -2.5 0 -50 -25 0 25 50 75 100 -50 125 -25 0 25 50 75 100 Junction Temperature (o C) Junction Temperature (o C) Quiescent current Quiescent standby current 12 125 90 VCC=12V 80 10 VCC=12V 70 60 VCC=5V Iqst-by (V) IQ (mA) 8 6 4 50 40 30 VCC=5V 20 2 10 0 0 -50 -25 0 25 50 75 100 125 -50 o Junction Temperature ( C) Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 -25 0 25 50 75 100 125 o Junction Temperature ( C) 8 www.anpec.com.tw APW1173 Typical Operating Characteristics (Cont.) Efficiency vs. Output Current at VIN=5V Efficiency vs. Output Current at VIN=12V 80% 78% 76% 74% Efficiency (%) 72% Efficiency (%) 70% 68% 66% 64% 62% 60% VO=1.8V VO=2.5V VO=3.3V 58% 56% 54% 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 90% 88% 86% 84% 82% 80% 78% 76% 74% 72% 70% 68% 66% VO=2.5V VO=3.3V VO=5V 64% 62% 60% 58% 56% 54% 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 Output Current (A) Output Current (A) VCE vs. ICE VFB vs. Temperature 1.5 1.241 1.240 1.4 1.239 1.3 VIN=5V 1.238 1.237 VFB (V) VCE (V) 1.2 1.1 1.0 VIN=12V 1.236 1.235 1.234 0.9 1.233 0.8 1.232 0.7 1.231 0.0 0.5 1.0 1.5 2.0 2.5 3.0 -50 Rev. A.5 - Aug., 2005 0 25 50 75 100 125 o ICE (A) Copyright ANPEC Electronics Corp. -25 Junction Temperature ( C) 9 www.anpec.com.tw APW1173 Typical Operating Characteristics (Cont.) Switching Frequency 585 Switching Frequenct (KHz) 565 545 525 505 485 465 445 425 -50 -25 0 25 50 75 100 125 Junction Temperature (o C) Operating waveforms 1. Power ON (no SS) : - VIN = 12V,VOUT = 3.3V - CIN = 22µF, COUT = 220µF, L = 15 µH 2. Power ON (external SS) : - VIN = 12V,VOUT = 3.3V - CIN = 22µF, COUT = 220µF, L = 15 µH IL IL V OUT V IN V OUT COMP COMP Ch1 : VOUT,1V/div Ch1 : VOUT,1V/div Ch2 : COMP,2V/div Ch2 : COMP,2V/div Ch3 : VIN,5V/div Ch3 : VIN,5V/div Ch4 : IL,2A/div Ch4 : IL,2A/div Time : 400us/div Time : 1ms/div Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 V IN 10 www.anpec.com.tw APW1173 Operating waveforms (Cont.) 3. Current Limit : - VIN = 12V,VOUT = 3.3V - CIN = 22µF, COUT = 220µF, L = 15 µH 4. Load Transient : - VIN = 12V,VOUT = 3.3V - CIN = 22µF, COUT = 220µF, L = 15 µH IOUT IOUT V OUT V OUT COMP Ch1 : VOUT,2V/div Ch1 : VOUT,200mV/div,offset 3.3V Ch2 : COMP,2V/div Ch2 : IOUT,1A/div,100mA-3A Ch3 : IOUT,2A/div Ch2 rising time : 4us Time : 2ms/div Ch2 falling time : 4us Time : 10us/div Functional Description Power-On-Reset comparator and compared with internal saw tooth wave. It generates a PWM control signal by the PWM comparator. The PWM signal feeds into the logic A Power-On-Reset circuit monitors input voltages at VCC pin to prevent wrong logic controls. The POR function initiates immediately by the inductor current with it’s limit after the supply voltage exceed firstly it’s threshold voltage after powering on. depends on the previous mechanism. Output Voltage Regulation Current Limit An error amplifier working with a temperature-compensated 1.235V reference. The error amplifier designed with high bandwidth and DC gain provides very fast transient response and less load regulation. It compares the reference with the feedback voltage and amplifies the difference in it’s output called error signal. The error signal feeds into the input terminal of PWM The APW1173 monitors the current flow through the pass element and limits the maximum output current to prevent damages during overload or short-circuit conditions. Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 circuit and turns on or off the pass element. The Buck type output stage regulates the correct output voltage Over-Voltage Protection (OVP) The over voltage protection is realized by using an 11 www.anpec.com.tw APW1173 Functional Description (Cont.) Over-Voltage Protection (OVP) (Cont.) The thermal protection function generates a control signal to shut off the APW1173. It prevents the damages caused by over heat situation. The thermal func-tion was acted when the temperature of chip reaching 160°C. A hysteresis of the thermal protection function is approximately 30°C, in order to avoid pass element turns on and off immediately. the current limit function acting and VOUT dropping. This results the switching frequency decreased. In the practical application, when the load current increase big enough such that current limit occurring. In this situation,more load current cause the output voltage get away the regulatory point and begin dropping until it’s limitation. In this time, the actual duty was very small in general. But the on time period limited by the minimum on time limitation of the control circuit. This on time limitation induce the load current runs away the limiting boundary. To prevent this drawback, the frequency fold back is used to ensure that load current was limited by the setup value. Voltage Feed Forward Inhibit Function The Voltage Feed Forward is acting when VCC goes higher than 10V. This will increases the upper bond of the internal sawtooth wave and results duty keeping constant. The change of the upper bond is linear and proportion with VCC. The Inhibit function disables when the Inhibit voltage lower than 1.3V. APW1173 entered the standby mode with Inhibit voltage higher than 1.4V. The quiescent current in the standby mode is less than 100uA to saving power. If the Inhibit pin left floating, the Inhibit voltage will be pull up by internal current source. internal comparator. The input of the OVP comparator connects to the feedback, that turns off the pass element when the OVP threshold is reached. This threshold is typically 25% higher than the feedback voltage Thermal protection Frequency Fold Back The Frequency Fold Back function acts when both Application Description Input Capacitor sary to use low-ESR capacitors. More capacitance reduce the variations of the input voltage of VCC pin. The APW1173 requires proper input capacitors to supply current surge during stepping load transients to prevent the input rail from dropping. Due to the wide range of input voltage, the input capacitor must be able to support the input operating voltage. Ultra-lowESR capacitors, such as ceramic chip capacitors, are very good for the input capacitors. An aluminum electrolytic capacitor (>100µF, ESR<300mΩ) is recommended as the input capacitor. It is not neces- Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 Inductor Inductor is an important component in the application. In the switching regulator, energy stored in the inductor by magnetic field when the pass element conducting. This behavior cause the ripple current cycle by cycle, the ripple current flowing through the output capacitor induce the output ripple voltage. In general, the ripple 12 www.anpec.com.tw APW1173 Application Description (Cont.) Inductor (Cont.) dimension of inductor to save the board space. In other way, devote the performance by higher ripple current. If select a greater inductor, the ripple current will be smaller and a better performance is got. This tradeoff is an useful method to decide a better performance or a smaller inductor size. current is usually fixed at 20%~40% of maximum output current,that is 0.6A~1.2A with maximum output current equal 3A. The value of inductor can approximate by (1) L= VIN − VCE − VO Ton ∆I (1) Output Capacitor The APW1173 requires a proper output capacitor to maintain stability and improve transient response over temperature and current. The output capacitor selection is dependent upon ESR (equivalent series resistance) and capacitance of the output capacitor over the operating temperature. Where VIN is the input voltage, VCE is the voltage across the pass element when it conduct, VO is the output voltage, ∆I is the ripple current flowing through the inductor and Ton is the on period that determined by VO and VIN. The exact Ton can obtained by (2) and (3) D= VO + VD VIN − VCE + VD (2) Consider the output ripple voltage that absorbed in the application.Output ripple voltage consist of two parts.It show as (4) Where VD is the forward voltage of the wheeling diode. Ton = DTS Vripple = V1 + V2 (3) In previously,use the parameter ∆I to decide the value of the inductor. As the same manner,use the parameter ∆I to approximate the value of output capacitor. The first part of output ripple voltage,V1,is related to the ESR of output capacitor.It show as (5) Where TS is the period of whole cycle. It equal 1/FS where FS is the switching frequency of APW1173. For example, VIN =12V, VO =3.3V, VD =0.7V, IO =3A, ripple current is IO(20%~40%) =0.6A~1.2A, VCE =1.2V, FS =250KHz D= 3.3V + 0.7V = 34.78% 12V − 1.2V + 0.7V V1 = ESR × ∆I by (2) V2 = For the worst case ripple current equal 0.6A ~ 1.2A 12V − 1.2V − 3.3V 0.696µs = 8.7 µH 0.6 A for ripple current is 0.6A… … L2 = by (1) for ripple current is 1.2A… … by (1) Use the worst case to approximate the minimum value of inductor. In worst ripple current condition, smaller Rev. A.5 - Aug., 2005 ∆I TS 8C (6) These two parameters determine the value of output ripple voltage and the efficiency. More output ripple voltage cause the efficiency decreased.The output ripple voltage means the energy loss in the ESR and the energy loss in the transition path while the energy stored and removed in the output capacitor.In other aspect,the ESR and the value of output capacitor gen 12V − 1.2V − 3.3V 0.696µs = 4.35µH 1.2 A Copyright ANPEC Electronics Corp. (5) The second part of output ripple voltage,V2,can calculated by (6) Ton = DTS = 34.78% × 2µs = 0.696 µs by (3) L1 = (4) 13 www.anpec.com.tw APW1173 Application Description (Cont.) PD = VD × I D × (1 − D ) Output Capacitor (Cont.) erate a zero to provide a positive phase for control loop.This zero improved the stability without extra PID compensator, if the zero is lower enough. Where V D is the forward voltage of the wheeling diode, ID is current flowing through the wheeling diode when it conducting. In the PCB layout,usually place the wheeling diode near the APW1173, the power dissipation of wheeling diode will increase the ambient temperature and limit the maximum power dissipation of APW1173.These power dissipations are the major energy loss in the voltage conversion. Switch diode APW1173 is an non-synchronous type buck regulator and needs a Shottky diode as the wheeling diode. This diode will conduct when the pass element turned off.Current flows through the diode in the conducted period, the order of the maximum peak current reaches few Amperes. The diode requires the ability to flow the great forward current. The peak forward current of the diode denote in the specification must great than 15A, and the conducting time in this situation must great than 8ms. 1N5818 is a suitable component. To improve the thermal resistance by increasing copper area is a suitable method. Design a copper area according to the following curve to improve the thermal resistance. Thermal Resistance of Junction to Ambient ( o C/W) 48 Thermal Consideration APW1173 is a switching regulator whose pass element inside, it have the ability to provide 3 Amperes.As the show in the block diagram, the structure of the pass element consist of a NPN and a PNP transistors. The voltage across the pass element, VCE, is about 0.8V to 1.3V in the light load to heavy load. The product of VCE and IL, where IL is current flowing through the inductor, generate thermal cause the junction temperature increased. The thermal stream conduct via the thermal pad of SOP-8-P to the printed circuit board.The power dissipation of APW1173 can be approximated by (7) 44 42 40 38 36 34 32 0 2 4 6 8 10 12 Top Copper Area (cm^2) Frequency Compensation In the Buck converter,there is a LPF(Low Pass Filter) in the output stage to filtering the switching noise. The LPF consist of an inductor and a capacitor. These two components generate the double poles in the frequency domain. Where VCE is the voltage across the pass element, IL is the current flowing through the inductor, D is the duty. TR and TF are the transition time. f natural = The wheeling diode is another thermal source. It’s power dissipation approximated by (8) Rev. A.5 - Aug., 2005 46 30 P = (VCE × I L × D ) + (VIN × I L × FS )(TR + TF ) (7) Copyright ANPEC Electronics Corp. (8) 1 2π LC (9) Where L is the inductance of the LPF and C is the capacitance of the output capacitor. These double poles 14 www.anpec.com.tw APW1173 Application Description (Cont.) L Frequency Compensation (Cont.) VOUT issue. cause the phase decrease rapidly at the natural frequency and lead the phase margin not enough to maintain the stable status. The stable issue improved by apply a zero in the frequency domain to increase the phase margin. ESR Loading CO U T Ceramic type FB PIN EA COMP PIN Consider the Figure-2, find the transfer function H(s) as: 1.235V H ( s) = RC1 SCOUT ( ESR) + 1 S LCOUT + SCOUT ( ESR) + 1 2 CC2 pole1, 2 = CC1 zero1 = Adding a resistor and a capacitor at the COMP pin is the simplest way to generate a zero. The placement of the components is the show of Figure-1. The frequency of the zero is f zero = 1 2πRC1CC1 Q= (11) CC 2 1 2π( ESR)COUT 1 L ( ESR) COUT The frequency response of the output stage show as Figure-3. Locate the zero before the natural frequency to compensate the phase. The another capacitor CC2 used to bypass the noise. In general 1 = CC1 10 2π LCOUT The pole1 and pole2 are the conjugate roots of the denominator and the zero1 is the root of the numerator. Find the Q factor from the quadratic function and the description of Q factor as above. (10) The relation of the zero and the natural frequency is f zero = 0.8 ⋅ f natural 1 0db (12) In the other applications, use the ceramic capacitor as the output capacitor is very popular. Because the small dimension of the ceramic capacitor save the PCB (Printed Circuit Board) area, the low ESR(Equivalent Series Resistance) of the ceramic one decrease the power dissipation of the output capacitor.But the serious drawbacks of the ceramic one is the stable slope=-40db/ decade 0d phase -90d -135d -180d f Pole1,2 Zero1 Figure-3 Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 15 www.anpec.com.tw APW1173 Application Description (Cont.) The frequency response of the PID compensator presented as Figure-5: Frequency Compensation (Cont.) The problem is the phase nearly –180 degrees at the natural frequency especially in the high Q situation. If the Q factor is high, the phase decrease vary sharp at the location of the double poles. This problem leads the regulator oscillating when use ceramic one as the output capacitor without compensation. The purpose of the compensation is saving the phase. The manner is added additional zeros to achieve the goal. A zero have the ability that contribute the maximum phase of 90 degrees. According this characteristic, needs two zeros to compensate the phase loss. The PID compensator is good for this.It shows as Figure-4. 0db slope=-20db/ decade 270d phase 180d 90d 45d 0d f C3 Zero2 Zero3 Pole3 Pole4 Figure-5 C2 R2 R3 The assumption is 10(zero2)<zero3,10(zero3)<pole3, 10(pole3)<pole4.In order to compensate the phase, place the two zeros closely and located before the natural frequency. In general C1 FB R1 EA zero 2 ≅ zero3 = k ⋅ pole1, 2 COMP (11) Vref Where k is a constant, the value of k is almost 0.7 to 0.8. The useful rules are: (1) Determine the value of C2,the value must smaller than 5nF to get fast response time. (2) Find R3 by the equation Figure-4 The transfer function H(s) is H ( s) = (SC2 R3 + 1)[SC1 (R1 + R2 ) + 1] S (SC1 R2 + 1)[SC 2C3 R3 + (C2 + C3 )] R3 = (2π ⋅ C2 ⋅ k ⋅ pole1, 2 ) −1 1 zero2 = 2π ⋅ C2 R3 (3) Determine the value of C1 from 470pF to 1uF. This range of C1 is for reference. (4) The range of pole3 is from 150KHz to 300KHz. Use this range to find the value of R2. (5) Find R1 by the equation 1 zero3 = 2π ⋅ C1 ( R1 + R2 ) pole3 = 1 2π ⋅ C1R2 R1 = (2π ⋅ C1 ⋅ k ⋅ pole1,2 ) −1 − R2 C2 + C3 pole4 = 2π ⋅ C2C3 R3 Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 (6) The location of pole4 is 5 times pole3. Use this result to find the value of R3. 16 www.anpec.com.tw APW1173 Layout Consideration 1. Please solder the Exposed Pad on the PCB.The heat generated by the power consumption will conduct by the thermal pad. 2. Please place the input capacitors for VCC pin nearly as close as possible. 3. Connect the switching inductor and the Schottky diode and OUT pin by a wide track. 4. Place the output capacitor close to the inductor as possible and with a wide and short track. 5.The thermal pad is needed to improve the power dissipation. VREF = 3.3V VOUT = 3.3V 1 2 L 22uH 3 4 COUT 100uF D1 1N5819 RC1 4.3K CC1 2.2nF Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 OUT VCC SYNC GND INH COMP VREF FB 8 7 6 5 APW1173 RF1 5.6K RF2 3.3K CIN 22uF V IN 4.8V to 22V CC2 220pF 17 www.anpec.com.tw APW1173 Packaging Information E E1 0.015X45 SOP-8-P pin ( Reference JEDEC Registration MS-012) H D1 e1 e2 D A1 A L 0.004max. Dim 1 Millimeters Inches Min. Max. Min. Max. A 1.35 1.75 0.053 0.069 A1 D 0 4.80 0.15 5.00 0 0.189 0.006 0.197 D1 E 3.00REF 3.80 0.118REF 4.00 0.150 2.60REF 0.157 E1 H 0.102REF 5.80 6.20 0.228 0.244 L e1 0.40 0.33 1.27 0.51 0.016 0.013 0.050 0.020 e2 1.27BSC 0.50BSC φ1 8° 8° Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 18 www.anpec.com.tw APW1173 Physical Specifications Terminal Material Lead Solderability Solder-Plated Copper (Solder Material : 90/10 or 63/37 SnPb), 100%Sn Meets EIA Specification RSI86-91, ANSI/J-STD-002 Category 3. Reflow Condition (IR/Convection or VPR Reflow) tp TP Critical Zone T L to T P Temperature Ramp-up TL tL Tsmax Tsmin Ramp-down ts Preheat 25 t 25 °C to Peak Time 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 (T L) - Time (tL) Peak/Classificatioon Temperature (Tp) Time within 5°C of actual Peak Temperature (tp) Ramp-down Rate Sn-Pb Eutectic Assembly Pb-Free Assembly 3°C/second max. 3°C/second max. 100°C 150°C 60-120 seconds 150°C 200°C 60-180 seconds 183°C 60-150 seconds 217°C 60-150 seconds See table 1 See table 2 10-30 seconds 20-40 seconds 6°C/second max. 6°C/second max. 6 minutes max. 8 minutes max. Time 25°C to Peak Temperature Notes: All temperatures refer to topside of the package .Measured on the body surface. Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 19 www.anpec.com.tw APW1173 Classification Reflow Profiles(Cont.) Table 1. SnPb Entectic Process – Package Peak Reflow Temperature s Package Thickness Volume mm 3 Volume mm 3 <350 ≥350 <2.5 mm 240 +0/-5°C 225 +0/-5°C ≥2.5 mm 225 +0/-5°C 225 +0/-5°C 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 +0°C* 260 +0°C* 260 +0°C* 1.6 mm – 2.5 mm 260 +0°C* 250 +0°C* 245 +0°C* ≥2.5 mm 250 +0°C* 245 +0°C* 245 +0°C* *Tolerance: The device manufacturer/supplier shall assure process compatibility up to and including the stated classification temperature (this means Peak reflow temperature +0°C. For example 260°C+0°C) at the rated MSL level. 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 245°C , 5 SEC 1000 Hrs Bias @ 125 °C 168 Hrs, 100 % RH , 121°C -65°C ~ 150°C, 200 Cycles VHBM > 2KV, VMM > 200V 10ms , Itr > 100mA Carrier Tape t D P Po E P1 Bo F W Ko Ao Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 D1 20 www.anpec.com.tw APW1173 Carrier Tape(Cont.) T2 J C A B T1 Application SOP-8-P A 330±1 Application SOP-8-P F 5.5 ± 0.1 B 62 ± 1.5 C 12.75 + 0.1 5 J 2 + 0.5 D D1 Po 1.55±0.1 1.55+ 0.25 4.0 ± 0.1 T1 12.4 +0.2 T2 2± 0.2 P1 Ao 2.0 ± 0.1 6.4 ± 0.1 W 12 + 0.3 - 0.1 Bo 5.2± 0.1 P 8± 0.1 E 1.75± 0.1 Ko t 2.1± 0.1 0.3±0.013 (mm) Cover Tape Dimensions Application SOP- 8-P Carrier Width 12 Cover Tape Width 9.3 Devices Per Reel 2500 Customer Service Anpec Electronics Corp. Head Office : 5F, No. 2 Li-Hsin Road, SBIP, Hsin-Chu, Taiwan, R.O.C. Tel : 886-3-5642000 Fax : 886-3-5642050 Taipei Branch : 7F, No. 137, Lane 235, Pac Chiao Rd., Hsin Tien City, Taipei Hsien, Taiwan, R. O. C. Tel : 886-2-89191368 Fax : 886-2-89191369 Copyright ANPEC Electronics Corp. Rev. A.5 - Aug., 2005 21 www.anpec.com.tw