《嵌入式应用开发》课程教学资源（文献资料）Advanced Monolithic Systems AMS1117 1A LOW DROPOUT VOLTAGE REGULATOR.pdf_大学文库

Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 Advanced AMS1117 Monolithic 1A LOW DROPOUT VOLTAGE REGULATOR Systems RoHs Compliant FEATURES APPLICATIONS • Three Terminal Adjustable or Fixed Voltages* • High Efficiency Linear Regulators 1.5V, 1.8V, 2.5V, 2.85V, 3.3V and 5.0V • Post Regulators for Switching Supplies • Output Current of 1A • 5V to 3.3V Linear Regulator • Operates Down to 1V Dropout • Battery Chargers • Line Regulation: 0.2% Max. • Active SCSI Terminators • Load Regulation: 0.4% Max. • Power Management for Notebook • SOT-223, TO-252 and SO-8 package available • Battery Powered Instrumentation GENERAL DESCRIPTION The The AMS1117 series of adjustable and fixed voltage regulators are designed to provide 1A output current and to operate down to 1V input-to-output differential. The dropout voltage of the device is guaranteed maximum 1.3V at maximum output current, decreasing at lower load currents. On-chip trimming adjusts the reference voltage to 1.5%. Current limit is also trimmed, minimizing the stress under overload conditions on both the regulator and power source circuitry. The AMS1117 devices are pin compatible with other three-terminal SCSI regulators and are offered in the low profile surface mount SOT-223 package, in the 8L SOIC package and in the TO-252 (DPAK) plastic package. ORDERING INFORMATION: PACKAGE TYPE OPERATING JUNCTION TO-252 SOT-223 8L SOIC TEMPERATURE RANGE AMS1117CD AMS1117 AMS1117CS -40 to 125° C AMS1117CD-1.5 AMS1117-1.5 AMS1117CS-1.5 -40 to 125° C AMS1117CD-1.8 AMS1117-1.8 AMS1117CS-1.8 -40 to 125° C AMS1117CD-2.5 AMS1117-2.5 AMS1117CS-2.5 -40 to 125° C AMS1117CD-2.85 AMS1117-2.85 AMS1117CS-2.85 -40 to 125° C AMS1117CD-3.3 AMS1117-3.3 AMS1117CS-3.3 -40 to 125° C AMS1117CD-5.0 AMS1117-5.0 AMS1117CS-5.0 -40 to 125° C *For additional available fixed voltages contact factory. PIN CONNECTIONS 3 PIN FIXED/ADJUSTABLE VERSION 1- Ground/Adjust 2- VOUT 3- VIN SOT-223 Top View 1 2 3 8L SOIC Top View 1 2 8 4 3 7 5 6 VOUT N/C VOUT GND/ADJ VOUT VOUT N/C VIN TAB IS OUTPUT TO-252 FRONT VIEW 1 2 3

Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 AMS1117 ABSOLUTE MAXIMUM RATINGS (Note 1) Power Dissipation Internally limited Soldering information Input Voltage 15V Lead Temperature (25 sec) 265°C Operating Junction Temperature Range Thermal Resistance Control Section -40°C to 125°C SO-8 package ϕ JA= 160°C/W Power Transistor -40°C to 125°C TO-252 package ϕ JA= 80°C/W Storage temperature - 65°C to +150°C SOT-223 package ϕ JA= 90°C/W* * With package soldering to copper area over backside ground plane or internal power plane ϕ JA can vary from 46°C/W to >90°C/W depending on mounting technique and the size of the copper area. ELECTRICAL CHARACTERISTICS Electrical Characteristics at IOUT = 0 mA, and TJ = +25°C unless otherwise specified. Parameter Device Conditions Min Typ Max Units Reference Voltage (Note 2) AMS1117 IOUT = 10 mA 1.5V≤ (VIN - VOUT) ≤ 12V 1.232 1.2125 1.250 1.250 1.268 1.2875 V V Output Voltage (Note 2) AMS1117-1.5 3.0V≤ VIN ≤ 12V 1.478 1.455 1.500 1.500 1.522 1.545 V V AMS1117-1.8 3.3V≤ VIN ≤ 12V 1.773 1.746 1.800 1.800 1.827 1.854 V V AMS1117-2.5 4.0V≤ VIN ≤ 12V 2.463 2.425 2.500 2.500 2.537 2.575 V V AMS1117-2.85 4.35V≤ VIN ≤ 12V 2.808 2.7645 2.850 2.850 2.892 2.9355 V V AMS1117-3.3 4.75V ≤ VIN ≤ 12V 3.251 3.201 3.300 3.300 3.349 3.399 V V AMS1117-5.0 6.5V ≤ VIN ≤ 12V 4.925 4.850 5.000 5.000 5.075 5.150 V V Line Regulation AMS1117 1.5V≤ (VIN - VOUT) ≤ 12V 0.015 0.035 0.2 0.2 % % AMS1117-1.5 3.0V≤ VIN ≤ 12V 0.3 0.6 5 6 mV mV AMS1117-1.8 3.3V≤ VIN ≤ 12V 0.3 0.6 5 6 mV mV AMS1117-2.5 4.0V≤ VIN ≤ 12V 0.3 0.6 6 6 mV mV AMS1117-2.85 4.35V≤ VIN ≤ 12V 0.3 0.6 6 6 mV mV AMS1117-3.3 4.75V≤ VIN ≤ 12V 0.5 1.0 10 10 mV mV AMS1117-5.0 6.5V≤ VIN ≤ 12V 0.5 1.0 10 10 mV mV Load Regulation (Notes 2, 3) AMS1117 (VIN - VOUT) =1.5V, 10mA ≤ IOUT ≤ 1A 0.1 0.2 0.3 0.4 % % AMS1117-1.5 VIN = 3V, 0 ≤ IOUT ≤ 1A 3 6 10 20 mV mV AMS1117-1.8 VIN = 3.3V, 0 ≤ IOUT ≤ 1A 3 6 10 20 mV mV AMS1117-2.5 VIN = 5V, 0 ≤ IOUT ≤ 1A 3 6 12 20 mV mV

AMS1117ELECTRICALCHARACTERISTICSElectrical Characteristics at Iour=0 mA, and T,=+25°C unless otherwise specified.DeviceConditionsMinTypMaxUnitsParameter3612mVLoad RegulationAMS1117-2.85VIN=4.35V,0≤loUT≤1A20mV(Notes 2, 3)315mvAMS1117-3.3ViN=4.75V,0≤lour≤1A725mV5mv20AMS1117-5.0ViN=6.5V,0≤louT≤1A1035mVV1.11.3Dropout VoltageAMS1117-1.5/-1.8/-2.5/-△VouT, △VREF =1%, louT= 1A (Note 4)2.85/-3.3/-5.0(VIN -Vour)9001,500mACurrent LimitAMS1117-1.5/-1.8/-2.5/-(VIN - Vour)= 1.5V1,1002.85/-3.3/-5.05AMS111710mAMinimum Load(Vin -Vour)=1.5V (Note 5)Current(ViN - Vour)= 1.5V5AMS1117-1.5/-1.8/-2.5/-11mAQuiescent Current2.85/-3.3/-5.06075dBRipple RejectionAMS1117f=120Hz,Cour=22μF Tantalum, lour=1A,(VIN-VouT)=3V,CAD)=10uFAMS1117-1.5/-1.8/-2.5/-6072dBf=120Hz,Cour=22μF Tantalum, lour = 1A,2.85ViN =4.35V6072dBAMS1117-3.3f=120Hz,Cour=22μF Tantalum, lour =1AViN =4.75V68dBf=120Hz, Cour= 22μF Tantalum, lour = 1A60AMS1117-5.0VIN =6.5V0.0080.04%WThermal RegulationAMS1117TA = 25°C, 30ms pulse55AMS1117μAAdjust Pin Currentlour =10mA, 1.5V≤(Vin - Vour)≤12V120μA50.2 AMS1117MAAdjust Pin CurrentIour =10mA, 1.5V≤ (ViN- Vour)≤ 12VChange0.5%Temperature Stability1%0.3Long Term StabilityTA=125°C, 1000Hrs%0.003RMS Output NoiseTA=25C,10Hz≤f ≤10kHz(% of Vour)All packagesThermal Resistance15°C/WJunction-to-CaseParameters identified with boldface type apply over the full operating temperature range.Note l: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. For guaranteed specifications and test conditions, see theElectrical Characteristics. The guaranteed specifications apply only for the test conditions listed.Note 2: Line and Load regulation are guaranteed up to the maximum power dissipation of 1.2 W for SOT-223, 2.2W for TO-252 and 780mW for 8-LeadSOIC. Power dissipation is determined by the input/output differential and the output current. Guaranteed maximum power dissipation will not be availableover the full input/output range.Note 3: See thermal regulation specifications for changes in output voltage due to heating effects. Line and load regulation are measured at a constantjunction temperature by low duty cycle pulse testing. Load regulation is measured at the output lead -1/8" from the package.Note 4: Dropout voltage is specified over the full output current range ofthe device.Note 5: Minimum load current is defined as the minimum output current required to maintain regulation. When 1.5V ≤ (Vin - Vour) ≤ 12V the device isguaranteed to regulate if the output current is greater than 10mA.Advanced Monolithic Systems, Inc.www.advanced-monolithic.comPhone(925)443-0722Fax(925)443-0723

Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 AMS1117 ELECTRICAL CHARACTERISTICS Electrical Characteristics at IOUT = 0 mA, and TJ = +25°C unless otherwise specified. Parameter Device Conditions Min Typ Max Units Load Regulation (Notes 2, 3) AMS1117-2.85 VIN = 4.35V, 0 ≤ IOUT ≤ 1A 3 6 12 20 mV mV AMS1117-3.3 VIN = 4.75V, 0 ≤ IOUT ≤ 1A 3 7 15 25 mV mV AMS1117-5.0 VIN = 6.5V, 0 ≤ IOUT ≤ 1A 5 10 20 35 mV mV Dropout Voltage (VIN - VOUT) AMS1117-1.5/-1.8/-2.5/- 2.85/-3.3/-5.0 ∆VOUT , ∆VREF = 1%, IOUT = 1A (Note 4) 1.1 1.3 V Current Limit AMS1117-1.5/-1.8/-2.5/- 2.85/-3.3/-5.0 (VIN - VOUT) = 1.5V 900 1,100 1,500 mA Minimum Load Current AMS1117 (VIN - VOUT) = 1.5V (Note 5) 5 10 mA Quiescent Current AMS1117-1.5/-1.8/-2.5/- 2.85/-3.3/-5.0 (VIN - VOUT) = 1.5V 5 11 mA Ripple Rejection AMS1117 f =120Hz , COUT = 22µF Tantalum, IOUT = 1A, (VIN-VOUT ) = 3V, CADJ =10µF 60 75 dB AMS1117-1.5/-1.8/-2.5/- 2.85 f =120Hz , COUT = 22µF Tantalum, IOUT = 1A, VIN = 4.35V 60 72 dB AMS1117-3.3 f =120Hz , COUT = 22µF Tantalum, IOUT = 1A VIN = 4.75V 60 72 dB AMS1117-5.0 f =120Hz , COUT = 22µF Tantalum, IOUT = 1A VIN = 6.5V 60 68 dB Thermal Regulation AMS1117 TA = 25°C, 30ms pulse 0.008 0.04 %W Adjust Pin Current AMS1117 IOUT =10mA , 1.5V≤ (VIN - VOUT) ≤ 12V 55 120 µA µA Adjust Pin Current Change AMS1117 IOUT =10mA, 1.5V≤ (VIN - VOUT) ≤ 12V 0.2 5 µA Temperature Stability 0.5 % Long Term Stability TA =125°C, 1000Hrs 0.3 1 % RMS Output Noise (% of VOUT ) TA = 25°C , 10Hz ≤ f ≤ 10kHz 0.003 % Thermal Resistance Junction-to-Case All packages 15 °C/W Parameters identified with boldface type apply over the full operating temperature range. Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Note 2: Line and Load regulation are guaranteed up to the maximum power dissipation of 1.2 W for SOT-223, 2.2W for TO-252 and 780mW for 8-Lead SOIC. Power dissipation is determined by the input/output differential and the output current. Guaranteed maximum power dissipation will not be available over the full input/output range. Note 3: See thermal regulation specifications for changes in output voltage due to heating effects. Line and load regulation are measured at a constant junction temperature by low duty cycle pulse testing. Load regulation is measured at the output lead ~1/8” from the package. Note 4: Dropout voltage is specified over the full output current range of the device. Note 5: Minimum load current is defined as the minimum output current required to maintain regulation. When 1.5V ≤ (VIN - VOUT) ≤ 12V the device is guaranteed to regulate if the output current is greater than 10mA

AMS1117APPLICATIONHINTSThe AMS1117 series of adjustable and fixed regulators are easy touse and are protected against short circuit and thermal overloadsD1Thermal protectioncircuitrywill shut-downtheregulator should+the junction temperature exceed 165°C at the sense point.Pin compatible with older three terminal adjustable regulators,these devices offer the advantage of a lower dropout voltage,moreAMS1117VouTprecise reference tolerance and improved reference stability withViNINOUTTtemperature.tLCorADJMR11StabilityKCHiTThe circuit design used in the AMS1117 series requires the use ofan output capacitor as part of the device frequency compensation.Theaddition of 22μF solid tantalum on the outputwill ensurestability for all operating conditions.Figure 1.When the adjustment terminal is bypassed with a capacitor toimprove the ripple rejection, the requirement for an outputcapacitor increases.The value of 22μF tantalum covers all cases ofOutput Voltagebypassing the adjustment terminal. Without bypassing theadjustment terminal smaller capacitors can be used with equallyThe AMS1117 series develops a 1.25V reference voltage betweengood results.the output and the adjust terminal. Placing a resistor between theseTo further improve stability and transient response of thesetwo terminals causes a constant current to flowthrough R1 anddevices larger values of output capacitor can be used.down through R2 to set the overall output voltage.This current isnormally the specified minimum load current of 1OmA.BecauseIADy is very small and constant itrepresents a small error and itProtection Diodescan usually be ignored.Unlike older regulators, the AMS1117 family does not need anyAMS1117protection diodes between the adjustment pin and the output andhVOUTINOUTfrom the output to the input to prevent over-stressing the die.HHADJVREFR1Intermal resistors are limiting the internal current paths on the1Y★ILAMS1117 adjustment pin, therefore even with capacitors on theTapi5SOμAadjustment pin no protection diode is needed to ensure deviceR2safety under short-circuit conditions.1Diodes between the input and output are not usually needed.VoUT=VREF(1+R2/R1)+IADJR2Microsecond surge currents of 50Ato 100A can be handled by theinternal diodebetweenthe inputand outputpinsof thedevice.Innormal operations it is difficult to get those values of surgeFigure 2.Basic Adjustable Regulatorcurrents even with the use of large output capacitances. If highvalue output capacitors are used, such as 1000μF to 5000μF andLoad Regulationthe input pin is instantaneously shorted to ground, damage canoccur. A diode from output to input is recommended, when aTrue remote load sensing it is not possible to provide, because thecrowbar circuit at the input of the AMS1117 is used (Figure 1).AMS1117 is a three terminal device.The resistance of the wireconnecting the regulator to the load will limit the load regulation.Thedata sheet specification forload regulation is measured at thebottom of thepackage.Negativesidesensingis atrue Kelvinconnection, with the bottom of the output divider returned to thenegative side of the load.The best load regulation is obtained when the top of the resistordividerR1is connected directlyto thecase notto the load.If R1were connected to the load, the effective resistance between theregulator and the load would be:Rpx (R2+RI).Rp=Parasitic Line ResistanceR1Phone(925)443-0722Advanced Monolithic Systems, Inc.www.advanced-monolithic.comFax(925)443-0723

Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 AMS1117 APPLICATION HINTS The AMS1117 series of adjustable and fixed regulators are easy to use and are protected against short circuit and thermal overloads. Thermal protection circuitry will shut-down the regulator should the junction temperature exceed 165°C at the sense point. Pin compatible with older three terminal adjustable regulators, these devices offer the advantage of a lower dropout voltage, more precise reference tolerance and improved reference stability with temperature. Stability The circuit design used in the AMS1117 series requires the use of an output capacitor as part of the device frequency compensation. The addition of 22µF solid tantalum on the output will ensure stability for all operating conditions. When the adjustment terminal is bypassed with a capacitor to improve the ripple rejection, the requirement for an output capacitor increases. The value of 22µF tantalum covers all cases of bypassing the adjustment terminal. Without bypassing the adjustment terminal smaller capacitors can be used with equally good results. To further improve stability and transient response of these devices larger values of output capacitor can be used. Protection Diodes Unlike older regulators, the AMS1117 family does not need any protection diodes between the adjustment pin and the output and from the output to the input to prevent over-stressing the die. Internal resistors are limiting the internal current paths on the AMS1117 adjustment pin, therefore even with capacitors on the adjustment pin no protection diode is needed to ensure device safety under short-circuit conditions. Diodes between the input and output are not usually needed. Microsecond surge currents of 50A to 100A can be handled by the internal diode between the input and output pins of the device. In normal operations it is difficult to get those values of surge currents even with the use of large output capacitances. If high value output capacitors are used, such as 1000µF to 5000µF and the input pin is instantaneously shorted to ground, damage can occur. A diode from output to input is recommended, when a crowbar circuit at the input of the AMS1117 is used (Figure 1). AMS1117 IN OUT ADJ + COUT 22µF VOUT R1 R2 CADJ 10µF D1 VIN Figure 1. Output Voltage The AMS1117 series develops a 1.25V reference voltage between the output and the adjust terminal. Placing a resistor between these two terminals causes a constant current to flow through R1 and down through R2 to set the overall output voltage. This current is normally the specified minimum load current of 10mA. Because IADJ is very small and constant it represents a small error and it can usually be ignored. AMS1117 IN OUT ADJ R1 R2 VOUT VREF VIN IADJ 50µA VOUT = VREF (1+ R2/R1)+IADJR2 Figure 2. Basic Adjustable Regulator Load Regulation True remote load sensing it is not possible to provide, because the AMS1117 is a three terminal device. The resistance of the wire connecting the regulator to the load will limit the load regulation. The data sheet specification for load regulation is measured at the bottom of the package. Negative side sensing is a true Kelvin connection, with the bottom of the output divider returned to the negative side of the load. The best load regulation is obtained when the top of the resistor divider R1 is connected directly to the case not to the load. If R1 were connected to the load, the effective resistance between the regulator and the load would be: RP x ( R2+R1 ) , RP = Parasitic Line Resistance R1

AMS1117APPLICATIONHINTSConnected as shown , Rp is not multiplied by the divider ratioThe total thermal resistance from junction to ambient can be aslow as 45°C/W.This requires a reasonable sized PC board with atRpleast on layer of copperto spread theheat across the board andPARASITICcouple it into the surrounding air.LINE RESISTANCEAMS1117Experiments have shown that the heat spreading copper layer doesVINMINOUTnot need to be electrically connected to the tab of the device. TheADJPC material can be very effective at transmitting heat between thepad area, attached to the pad of the device, and a ground planeMRItMlayereitherinsideorontheoppositesideoftheboard.Althoughthe actual thermal resistance of the PC material is high, the2Length/Area ratio of the thermal resistance between layers issmall.The data in Table 1, was taken using 1/16" FR-4 board with1 oz.copper foil, and it can be used as a rough guideline for>R2Westimating thermal resistance.For each application the thermal resistance will be affected bythermal interactions with other components on the board. Todetermine the actualvaluesomewillbeexperimentationnecessaryThe power dissipation of the AMS1117 is equal to:*CONNECTR1TOCASEPp =(VIN - Vour)(IouT)CONNECTR2TOLOADMaximum junction temperature will be equal to:Figure3.Connections forBest Load RegulationT, = Ta(MAx) + Pp(Thermal Resistance (junction-to-ambient)Maximum junction temperaturemustnotexceed125°CIn the case of fixed voltage devices the top of RI is connectedKelvin internally, and the ground pin can be used for negative sidesensing.Ripple RejectionThe ripple rejection values are measured with the adjustment pinThermal Considerationsbypassed.The impedance of the adjust pin capacitor at the ripplefrequencyshouldbelessthanthe valueofR1(normally10o2toThe AMS1117 series have internal power and thermal limiting2002)for a proper bypassing and ripple rejection approaching thecircuitry designed to protect the device under overload conditions.values shown. The size of the required adjust pin capacitor is aHowever maximum junction temperature ratings of 125°C shouldfunction of the input ripple frequency.If R1=1002 at 120Hz thenot be exceeded under continuous normal load conditions.adjust pin capacitor should be >13μF.At 10kHzonly0.16μF isCareful consideration must be given to all sources of thermalneeded.resistancefromjunction to ambient.For the surface mountpackage SOT-223 additional heat sources mounted near the deviceThe ripple rejection will be a function of output voltage, in circuitsmust be considered. The heat dissipation capability of the PCwithout an adjust pin bypass capacitor.The output ripple willboard and its copper traces is used as a heat sink for the device.increasedirectlyasaratioof theoutputvoltagetothereferenceThe thermal resistance from thejunctionto the tabfor theVoltage (VoUT / VREF).AMS1117 is15°C/W.Thermal resistancefromtabtoambientcanbeas lowas 30°C/WTable 1.COPPERAREATHERMAL RESISTANCETOPSIDE*BACK SIDEBOARDAREA(JUNCTION-TO-AMBIENT)2500Sq.mm2500Sq.mm2500Sq.mm55°C/W1000Sq.mm2500Sq.mm2500 Sq.mm55C/W225 Sq.mm2500 Sq.mm2500Sq.mm65C/W100 Sq.mm2500Sq.mm2500 Sq.mm80°C/W1000 Sq.mm1000 Sq.mm1000 Sq.mm60°C/W01000Sq.mm1000 Sq.mm65°C/W* Tab of device attached to topside copper.Phone(925)443-0722Advanced Monolithic Systems, Inc.www.advanced-monolithic.comFax(925)443-0723

Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 AMS1117 APPLICATION HINTS Connected as shown , RP is not multiplied by the divider ratio AMS1117 IN OUT ADJ R1* RL R2* VIN RP PARASITIC LINE RESISTANCE *CONNECT R1 TO CASE CONNECT R2 TO LOAD Figure 3. Connections for Best Load Regulation In the case of fixed voltage devices the top of R1 is connected Kelvin internally, and the ground pin can be used for negative side sensing. Thermal Considerations The AMS1117 series have internal power and thermal limiting circuitry designed to protect the device under overload conditions. However maximum junction temperature ratings of 125°C should not be exceeded under continuous normal load conditions. Careful consideration must be given to all sources of thermal resistance from junction to ambient. For the surface mount package SOT-223 additional heat sources mounted near the device must be considered. The heat dissipation capability of the PC board and its copper traces is used as a heat sink for the device. The thermal resistance from the junction to the tab for the AMS1117 is 15°C/W. Thermal resistance from tab to ambient can be as low as 30°C/W. The total thermal resistance from junction to ambient can be as low as 45°C/W. This requires a reasonable sized PC board with at least on layer of copper to spread the heat across the board and couple it into the surrounding air. Experiments have shown that the heat spreading copper layer does not need to be electrically connected to the tab of the device. The PC material can be very effective at transmitting heat between the pad area, attached to the pad of the device, and a ground plane layer either inside or on the opposite side of the board. Although the actual thermal resistance of the PC material is high, the Length/Area ratio of the thermal resistance between layers is small. The data in Table 1, was taken using 1/16” FR-4 board with 1 oz. copper foil, and it can be used as a rough guideline for estimating thermal resistance. For each application the thermal resistance will be affected by thermal interactions with other components on the board. To determine the actual value some experimentation will be necessary. The power dissipation of the AMS1117 is equal to: PD = ( VIN - VOUT )( IOUT ) Maximum junction temperature will be equal to: TJ = TA(MAX) + PD(Thermal Resistance (junction-to-ambient)) Maximum junction temperature must not exceed 125°C. Ripple Rejection The ripple rejection values are measured with the adjustment pin bypassed. The impedance of the adjust pin capacitor at the ripple frequency should be less than the value of R1 (normally 100Ω to 200Ω) for a proper bypassing and ripple rejection approaching the values shown. The size of the required adjust pin capacitor is a function of the input ripple frequency. If R1=100Ω at 120Hz the adjust pin capacitor should be >13µF. At 10kHz only 0.16µF is needed. The ripple rejection will be a function of output voltage, in circuits without an adjust pin bypass capacitor. The output ripple will increase directly as a ratio of the output voltage to the reference voltage (VOUT / VREF ). Table 1. COPPER AREA THERMAL RESISTANCE TOP SIDE* BACK SIDE BOARD AREA (JUNCTION-TO-AMBIENT) 2500 Sq. mm 2500 Sq. mm 2500 Sq. mm 55°C/W 1000 Sq. mm 2500 Sq. mm 2500 Sq. mm 55°C/W 225 Sq. mm 2500 Sq. mm 2500 Sq. mm 65°C/W 100 Sq. mm 2500 Sq. mm 2500 Sq. mm 80°C/W 1000 Sq. mm 1000 Sq. mm 1000 Sq. mm 60°C/W 1000 Sq. mm 0 1000 Sq. mm 65°C/W * Tab of device attached to topside copper