APW1172

APW1172 ANPEC | Alldatasheet

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 21

Technical content

Features

• Consumer: STB, DVD, TV, VCR, Car Radio, LCD monitors
• Networking: XDSL, Modems, DC-DC Modules
• Computer: Printers, Audio/Graphic Cards, Optical Storage, Hard Disk Drive
• Industrial: Chargers, Car Battery DC-DC Converters
• 2.5A Internal Switch
• Operating Input Voltage from 4.8V to 22V
• 3.3V ±2% Reference Voltage
• Output Voltage : APW1172 - adjustable from 1.235V to 20V
• Low Dropout Operation: 100% Duty Cycle
• 250KHz 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
• Over-Voltage Protection
• Lead Free Available (RoHS Compliant)

Applications

The APW1172 is a step down monolithic power switching regulator with a switching current limit of 3.8A so it is able to deliver more than 2.5A 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 250KHz. 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. General Description = Thermal Pad (connected to GND plane for better heat dissipation) SOP-8-P (Top View) VCC GND VREF FB OUT SYNC INH COMP

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw2 Absolute Maximum Ratings Ordering and Marking Information 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. APW1172 Handling Code Temp. Range Package Code 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 APW1172 KA : APW1172 XXXXX XXXXX - Date Code Lead Free Code ° ° Block Diagram Voltages Monitor VREF Buffer Peak to Peak Current Limit Oscillator Frequency Shifter Inhibit Driver INH COMP FB SYNC VREF VCC OUT GND VREF =1.235V OVP E/A PWM 1.25VREF Thermal Protection D Q Ck Symbol Parameter Value Unit VCC Input voltage (VCC to GND) 25 V VOUT Output DC voltage -1 to 25 V VIO COMP and FB to GND -0.7 ~ VCC V 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.4 - Aug., 2005 APW1172 www.anpec.com.tw3 Pin Function Description No. PIN Description 1 OUT Regulator Output. 2 SYNC Master/Slave synchonization. 3 INH 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. 4 COMP E/A output for frequency compensation. 5 FB Feedback input. Connecting directly to this pin results in an output voltage of 1.235V(APW1172). An external resistive divider is required for higher output voltages. 6 VREF 3.3V reference voltage ou tput, no Capacitor Is requested for stability. 7 GND Ground. 8 VCC Unregulated DC input voltage. Thermal Characteristics Symbol Parameter Value Unit θ JA Junction to ambient thermal resistance in free air 45.7 °C/W The * denotes the specifications that apply over TA = -40 ~ 85oC. Typical values are at TA = 25oC. VCC = 12V unless otherwise specified.

Electrical Characteristics

Symbol Parameter Test condition Min Typ Max Unit VCC Operating input voltage range VO = 1.235V; IO = 2A * 4.7 22 V UVLO threshold voltage VCC rising * 3.8 4.2 4.6 V VUVLO Hysteresis 0.3 V Vd Dropout voltage VCC = 4.8V; IO = 2A * 1.0 1.2 V ILIM Maximum limiting current VCC = 4.8V to 22V * 3.3 3.8 4.3 A * 200 250 300 fs Switching frequency Main design 205 250 295 KHz Duty cycle 0 100 % * 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.

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw4 APW1172 Symbol Parameter Test condition Min Typ Max Unit Dynamic Characteristics 1.22 1.235 1.25 VFB Voltage feedback APW1172 4.8V < VCC < 22V, 20Ma < IO < 2A * 1.198 1.235 1.272 V η Efficiency VO = 5V, VCC = 12V, IOUT = 1A 84 % DC Characteristics Iqop Total Operating Quiescent Current * 12 mA Iq Quiescent Current Duty Cycle = 0; VFB = 1.5V 10 mA VINH > 2.2V * 50 100 µA Iqst-by Total Stand-by Quiescent Current VCC = 22V; VINH > 2.2V * 80 150 µA Inhibit Device ON 1.1 1.3 1.5 V VINH INH Threshold Voltage 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 Error Amplifier VOH High Level Output Voltage VFB = 1V 3.5 3.8 V VOL Low Level Output Voltage VFB = 1.5V 0.4 V IO source Source Output Current VCOMP = 1.9V; VFB = 1V 200 300 µA IO sink Sink Output Current VCOMP = 1.9V; VFB = 1.5V 1 1.5 mA IFB Source Bias Current VFB = 1.5V 2.5 4 µA Maximum FB Voltage IFB = 0µA 2.1 V gm 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 2.5 VREF V Low Input Voltage VCC = 4.8V to 22V 0.74 V VSYNC = 0.74V 0.11 0.25 Slave Sink Current VSYNC = 2.33V 0.21 0.45 mA Master Output Amplitude ISOURCE = 3mA 2.75 3 V Output Pulse Width No load, VSYNC = 1.65V 0.2 0.35 µs Electrical Characteristics (Cont.) The * denotes the specifications that apply over TA = -40 ~ 85oC. Typical values are at TA = 25oC. VCC = 12V unless otherwise specified.

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw5 APW1172 Symbol Parameter Test condition Min Typ Max Unit Reference Section IREF = 0mA 3.234 3.3 3.366 V VREF VREF Output Voltage IREF = 0mA to 5mA, VCC = 4.4A to 22V * 3.2 3.3 3.399 V Line Regulation IREF = 0mA, VCC = 4.4A to 22V 5 10 mV Load Regulation IREF = 0mA to 5mA 8 15 mV Short Circuit Current 10 18 30 mA Other Thermal Limiting Protection 160 °C Hysteresis 30 °C Over-Voltage Protection Threshold Voltage VCOMP = 0.8V * 120 125 130 % Electrical Characteristics (Cont.) Typical Application Circuit L 22uH 1N5819 VIN 4.8V to 22V CIN 22uF VOUT = 3.3V RF1 5.6K RF2 3.3K COUT 100uF VREF = 3.3V RC1 4.3K CC1 2.2nF CC2 220pF APW1172 OUT1 SYNC INH COMP GND VCC FB VREF 1N4148 1uF 137K Soft Start Circuit The * denotes the specifications that apply over TA = -40 ~ 85oC. Typical values are at TA = 25oC. VCC = 12V unless otherwise specified.

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw6 Other Application Circuits Dual output voltage application BuckBoost regulator L 22uH 1N5819 VIN=5VCIN 22uF VOUT1 = 3.3V RF1 5.6K RF2 3.3K COUT1 100uF VREF = 3.3V RC1 4.3K CC1 2.2nF CC2 220pF APW1172 OUT1 SYNC INH COMP GND VCC FB VREF 1N4148VOUT2 = 5V N1/N2=2 COUT2 47uF L 15uH 1N5819 CIN2 22uF 25V VOUT = -12V RF1 2.7K RF2 24K COUT 100uF VREF = 3.3V RC1 4.3K CC1 2.2nF CC2 220pF APW1172 OUT1 SYNC INH COMP GND VCC FB VREF CIN1 22uF VIN=5V

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw7 3.20 3.22 3.24 3.26 3.28 3.30 3.32 3.34 3.36 3.38 3.40 -50 -25 0 25 50 75 100 125 -16 -14 -12 -10 -50 -25 0 25 50 75 100 125 -50 -25 0 25 50 75 100 125 -16 -14 -12 -10 -50 -25 0 25 50 75 100 125 Typical Operating Characteristics Junction Temperature (o C) Junction Temperature (o C) Line regulation (mV) Load regulation (mV) Load regulation of VREFLine regulation of VREF Junction Temperature (o C)Junction Temperature (o C) Short circuit current (mA) VREF (V) VREFShort circuit current of VREF

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw8 -50 -25 0 25 50 75 100 125 -50 -25 0 25 50 75 100 125 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 -50 -25 0 25 50 75 100 125 100 150 200 250 300 -50 -25 0 25 50 75 100 125 Typical Operating Characteristics (Cont.) Junction Temperature (o C) Junction Temperature (o C) Source current (uA) Sink current (mA) Sink ability of EASource ability of EA Junction Temperature (o C)Junction Temperature (o C) IQ (mA) Iqst-by (V) Quiescent standby currentQuiescent current VCC=12VVCC=12V VCC=5VVCC=5V VCC=12VVCC=12V VCC=5VVCC=5V

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw9 1.231 1.232 1.233 1.234 1.235 1.236 1.237 1.238 1.239 1.240 1.241 -50 -25 0 25 50 75 100 125 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 Typical Operating Characteristics (Cont.) ICE (A) VCE (V) VCE vs. ICE VIN=12VVIN=12V VIN=5VVIN=5V Junction Temperature (o C) VFB (V) VFB vs. Temperature Output Current (A) Output Current (A) Efficiency (%) Efficiency (%) Efficiency vs. Output Current at VIN=12VEfficiency vs. Output Current at VIN=5V 60% 62% 64% 66% 68% 70% 72% 74% 76% 78% 80% 60% 62% 64% 66% 68% 70% 72% 74% 76% 78% 80% 82% 84% 86%

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw10 Typical Operating Characteristics (Cont.) Junction Temperature (o C) Switching Frequenct (KHz) Switching Frequency 244 246 248 250 252 254 256 258 -50 -25 0 25 50 75 100 125 Operating waveforms Ch1 : VOUT,1V/div Ch2 : COMP,2V/div Ch3 : VIN,5V/div Ch4 : IL,2A/div Time : 400us/div Ch1 : VOUT,1V/div Ch2 : COMP,2V/div Ch3 : VIN,5V/div Ch4 : IL,2A/div Time : 1ms/div 2. Power ON (external SS) : - VIN = 12V,VOUT = 3.3V - CIN = 22µF, COUT = 220µF, L = 15 µH 1. Power ON (no SS) : - VIN = 12V,VOUT = 3.3V - CIN = 22µF, COUT = 220µF, L = 15 µH VOUT VIN IL COMP VOUT VIN IL COMP IL VOUT VIN COMP IL VOUT VIN COMP

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw11 Ch1 : VOUT,200mV/div,offset 3.3V Ch2 : IOUT,1A/div,100mA-3A Ch2 rising time : 4us Ch2 falling time : 4us Time : 10us/div Ch1 : VOUT,2V/div Ch2 : COMP,2V/div Ch3 : IOUT,2A/div Time : 2ms/div 4. Load Transient : - VIN = 12V,VOUT = 3.3V - CIN = 22µF, COUT = 220µF, L = 15 µH 3. Current Limit : - VIN = 12V,VOUT = 3.3V - CIN = 22µF, COUT = 220µF, L = 15 µH IOUT VOUT IOUT VOUT Operating waveforms (Cont.) Functional Description Power-On-Reset 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. Output Voltage Regulation An error amplifier working with a temperature-compen- sated 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 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 circuit and turns on or off the pass element. The Buck type output stage regulates the correct output voltage depends on the previous mechanism. Current Limit The APW1172 monitors the current flow through the pass element and limits the maximum output current to prevent damages during overload or short-circuit conditions. Over-Voltage Protection (OVP) The over voltage protection is realized by using an COMPCOMP V OUTV OUT IOUTIOUT

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw12 Functional Description (Cont.) 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 The thermal protection function generates a control signal to shut off the APW1172. It prevents the damages caused by over heat situation. The thermal function 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. Voltage Feed Forward 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. Frequency Fold Back The Frequency Fold Back function acts when both the current limit function acting and VOUT dropping. This results the switching frequency decreased. In the prac- tical 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 cur- rent was limited by the setup value. Inhibit Function The Inhibit function disables when the Inhibit voltage lower than 1.3V. APW1172 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. Over-Voltage Protection (OVP) (Cont.) Application Description Input Capacitor The APW1172 requires proper input capacitors to sup- ply 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-low- ESR 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 necessary to use low-ESR capacitors. More capacitance reduce the variations of the input voltage of VCC pin. 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

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw13 Application Description (Cont.) (3)Son DTT = (3)Son DTT = (2) DCEIN DO VVV VVD +− += (2) DCEIN DO VVV VVD +− (1)on OCEIN TI VVVL Δ −−= (1)on OCEIN TI VVVL Δ −−= %78.34V7.0V2.1V12 V7.0V3.3D =+− V7.0V3.3D =+− += by (2) s3912.1s4%78.34DTT Son µ=µ×== by (3)s3912.1s4%78.34DTT Son µ=µ×== by (3) H39.17s3912.1A6.0 V3.3V2.1V12L1 µ=µ−−= by (1) H695.8s3912.1A2.1 V3.3V2.1V12L2 µ=µ−−= by (1) H39.17s3912.1A6.0 V3.3V2.1V12L1 µ=µ−−= by (1) H695.8s3912.1A2.1 V3.3V2.1V12L2 µ=µ−−= by (1) output capacitor induce the output ripple voltage. In general, the ripple 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) Where VIN is the input voltage, VCE is the voltage across the pass element when it conduct, VO is the output voltage, Δ 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) Where VD is the forward voltage of the wheeling diode. Where TS is the period of whole cycle. It equal 1/FS where FS is the switching frequency of APW1172. 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 For the worst case ripple current equal 0.6A ~ 1.2A for ripple current is 0.6A… … for ripple current is 1.2A… … Use the worst case to approximate the minimum value of inductor. In worst ripple current condition, smaller 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. Output Capacitor The APW1172 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. Consider the output ripple voltage that absorbed in the application.Output ripple voltage consist of two parts.It show as (4) In previously,use the parameter Δ I to decide the value of the inductor. As the same manner,use the parameter Δ 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) The second part of output ripple voltage,V2,can calculated by (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 Inductor (Cont.) (5)IESRV Δ×=1 (5)IESRV Δ×=1 S2 TC8 IV Δ= (6)S2 TC8 IV Δ= (6)

21 VVVripple += (4)21 VVVripple += (4)

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw14 0 2 4 6 8 10 12 Application Description (Cont.) ))(()( FRSLINLCE TTFIVDIVP +××+××= (7)))(()( FRSLINLCE TTFIVDIVP +××+××= (7) generate 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. Switch diode APW1172 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. Thermal Consideration APW1172 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 APW1172 can be approximated by (7) 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. The wheeling diode is another thermal source. It’s power dissipation approximated by (8) Output Capacitor (Cont.) Where VD 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 APW1172, the power dissipation of wheeling diode will increase the ambient temperature and limit the maximum power dissipation of APW1172.These power dissipations are the major energy loss in the voltage conversion. 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. 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 L is the inductance of the LPF and C is the capacitance of the output capacitor. These double poles LC fnatural 1= (9) LC fnatural 1= (9) Top Copper Area (cm^2) Thermal Resistance of Junction to Ambient (o C/W) )1( DIVP DDD −××= (8)

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw15 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. 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 The relation of the zero and the natural frequency is Locate the zero before the natural frequency to compensate the phase. The another capacitor CC2 used to bypass the noise. In general 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 issue. Application Description (Cont.) Frequency Compensation (Cont.) 112 CC zero CRf p= (10) 112 CC zero CRf p= (10) (11)naturalzero ff ⋅= 8.0 (11)naturalzero ff ⋅= 8.0 Consider the Figure-2, find the transfer function H (s) as: 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. The frequency response of the output stage show as Figure-3. CC CC = (12)12 CC CC = (12) ESR COUT L Loading V OUT Ceramic type Figure-3 EA FB PIN 1.235V COMP PIN RC1 CC1 CC2 OUT OUT OUT OUTOUT OUT C L ESRQ CESRzero LC pole ESRSCLCS ESRSCsH )(2 1)( 1)()( 2,1 π f slope=-40db/ decade 0db -180d Pole1,2 Zero1 phase-90d -135d

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw16 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 com- pensator is good for this.It shows as Figure-4. The transfer function H(s) is The frequency response of the PID compensator pre- Application Description (Cont.) Frequency Compensation (Cont.) Vref C1R2 R3C2 COMP EA FB Figure-4 ( ) ( )[ ] ( ) ( )[ ]3233221 21132 11)( CCRCSCRSCS RRSCRSCsH +++ +++= 332 211 )(2 RCC CCpole RCpole RRCzero RCzero +⋅= p p p p sented as Figure-5: 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 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 (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 (6) The location of pole4 is 5 times pole3. Use this result to find the value of R3. f slope=-20db/ decade0db 180d Pole3Zero2 phase 90d 45d 270d Pole4Zero3 Figure-5 2,132 polekzerozero ⋅=≅ (11)2,132 polekzerozero ⋅=≅ (11) 2,123 )2( −⋅⋅⋅= polekCR p 2,111 )2( RpolekCR −⋅⋅⋅π= −

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw17 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. L 22uH 1N5819 V IN 4.8V to 22V CIN 22uF VOUT = 3.3V RF1 5.6K RF2 3.3K COUT 100uF VREF = 3.3V RC1 4.3K CC1 2.2nF CC2 220pF APW1172 OUT1 SYNC INH COMP GND VCC FB VREF

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw18 Packaging Information Millimeters Inches Dim Min. Max. Min. Max. A 1.35 1.75 0.053 0.069 A1 0 0.15 0 0.006 D 4.80 5.00 0.189 0.197 D1 3.00REF 0.118REF E 3.80 4.00 0.150 0.157 E1 2.60REF 0.102REF H 5.80 6.20 0.228 0.244 L 0.40 1.27 0.016 0.050 e1 0.33 0.51 0.013 0.020 e2 1.27BSC 0.50BSC φ 1 8° 8° SOP-8-P pin ( Reference JEDEC Registration MS-012) HE e1 e2 0.015X45 D AA1 0.004max. L

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw19 t 25 C to Peak tp Ramp-up tL Ramp-down ts Preheat Tsmax Tsmin TL TP Temperature Time Critical Zone TL to T P Physical Specifications Terminal Material Solder-Plated Copper (Solder Material : 90/10 or 63/37 SnPb) , 100%Sn Lead Solderability Meets EIA Specification RSI86 -91, ANSI/J-STD-002 Category 3. Reflow Condition (IR/Convection or VPR Reflow) Classification Reflow Profiles Profile Feature Sn-Pb Eutectic Assembly Pb-Free Assembly Average ramp-up rate (TL to TP) 3°C/second max. 3°C/second max. Preheat - Temperature Min (Tsmin) - Temperature Max (Tsmax) - Time (min to max) (ts) 100°C 150°C 60-120 seconds 150°C 200°C 60-180 seconds Time maintained above: - Temperature (TL) - Time (tL) 183°C 60-150 seconds 217°C 60-150 seconds Peak/Classificatioon Temperature (Tp) See table 1 See table 2 Time within 5°C of actual Peak Temperature (tp) 10-30 seconds 20-40 seconds Ramp-down Rate 6°C/second max. 6°C/second max. Time 25°C to Peak Temperature 6 minutes max. 8 minutes max. Note: All temperatures refer to topside of the package .Measured on the body surface.

Copyright  ANPEC Electronics Corp. Table 1. SnPb Entectic Process – Package Peak Reflow Temperature s Table 2. Pb -free Process – Package Classification Reflow Temperatures including the stated classification temperature (this means Peak reflow temperature +0 °C. For example 260 °C+0 °C) at the rated MSL level.

Copyright  ANPEC Electronics Corp. Rev. A.4 - Aug., 2005 APW1172 www.anpec.com.tw21 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 Cover Tape Dimensions Application Carrier Width Cover Tape Width Devices Per Reel SOP- 8-P 12 9.3 2500 Carrier Tape(Cont.) A J B C Application A B C J T1 T2 W P E SOP-8-P 330±1 62 ± 1.5 12.75 + 0.1 5 - 0.1 8± 0.1 1.75± 0.1 Application F D D1 Po P1 Ao Bo Ko t (mm)