AMS1117中文版本
LM1117
800mA
Low-Dropout Linear Regulator
General Description
The LM1117is a series of low dropout voltage regulators with a dropout of 1.2V at 800mA of load current.It has the same pin-out as National Semiconductor’s industry standard LM317.
The LM1117is available in an adjustable version,which can set the output voltage from 1.25V to 13.8V with only two ex-ternal resistors.In addition,it is also available in three fixed voltages,2.85V,3.3V,and 5V.
The LM1117offers current limiting and thermal shutdown.Its circuit includes a zener trimmed bandgap reference to as-sure output voltage accuracy to within ±1%.
The LM1117series is available in SOT-223,TO-220,and TO-252D-PAK packages.A minimum of 10μF tantalum ca-pacitor is required at the output to improve the transient re-sponse and stability.
Features
n Available in 2.85V,3.3V,5V,and Adjustable Versions n Space Saving SOT-223Package
n Current Limiting and Thermal Protection n Output Current 800mA n Temperature Range 0?C to 125?C n Line Regulation 0.2%(Max)n
Load Regulation 0.4%(Max)
Applications
n 2.85V Model for SCSI-2Active Termination n Post Regulator for Switching DC/DC Converter n High Efficiency Linear Regulators n Battery Charger
n
Battery Powered Instrumentation
Typical Application
Active Terminator for SCSI-2Bus
Fixed Output Regulator
1
Ordering
Information
Package
Temperature Range Packing
0?C to +125?C 3-lead SOT-223
LM1117-ADJ -223 Tape and Reel LM1117-2.85-223 T ape and Reel
LM1117-3.3-223 Tape and Reel LM1117-5.0-223
Tape and Reel
3-lead TO-220
LM1117-ADJ -220 Rails 5 lead available
LM1117-2.85-220 Rails suffix add 220-5L LM1117-3.3-220 Rails LM1117-5.0-220
Rails
3-lead TO-252
LM1117-ADJ -252 Tape and Reel 5 lead available LM1117-2.85-252 Tape and Reel suffix add 252-5L LM1117-3.3-252 Tape and Reel LM1117-5.0-252
Tape and Reel
Block Diagram
2
Connection Diagrams
SOT-223
DS100919-4
Top View TO-220
DS100919-2
Top View TO-252
DS100919-38
Top View
3
Absolute Maximum Ratings
(Note
1)
If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/Distributors for availability and specifications.Maximum Input Voltage (V IN to GND)LM1117-ADJ,LM1117-3.3,LM1117-5.0
20V
Power Dissipation (Note 2)Internally Limited
Junction Temperature (T J )(Note 2)
150?C
Storage Temperature Range -65?C to 150?C
Lead Temperature
TO-220Package 260?C,10sec SOT-223Package 260?C,4sec
ESD Tolerance (Note 3)
2000V
Operating Ratings (Note 1)
Input Voltage (V IN to GND)LM1117-ADJ,LM1117-3.3,LM1117-5.015V LM1117-2.85
10V
Junction Temperature Range (T J )(Note 2)
0?C to 125?C
Electrical Characteristics
Typicals and limits appearing in normal type apply for T J
=25?C.Limits appearing in Boldface type apply over the entire junc-tion temperature range for operation,0?C to 125?C.Symbol Parameter Conditions
Min (Note 5)Typ (Note 4)Max (Note 5)Units V REF
Reference Voltage
LM1117-ADJ
I OUT =10mA,V IN -V OUT =2V,T J =25?C 10mA ≤I OUT ≤800mA,1.4V ≤V IN -V OUT ≤10V
1.2381.225
1.2501.250
1.2621.270
V V
V OUT Output Voltage
LM1117-2.85
I OUT =10mA,V IN =4.85V,T J =25?C O ≤I OUT ≤800mA,4.25V ≤V IN ≤10V O ≤I OUT ≤500mA,V IN =4.10V 2.8202.7902.790 2.8502.8502.850 2.8802.9102.910V V V LM1117-3.3
I OUT =10mA,V IN =5V T J =25?C O ≤I OUT ≤800mA,4.75V ≤V IN ≤10V 3.2673.235 3.3003.300 3.3333.365V V LM1117-5.0
I OUT =10mA,V IN =7V,T J =25?C O ≤I OUT ≤800mA,6.5V ≤V IN ≤12V
4.9504.900
5.0005.000 5.0505.100V V ?V OUT
Line Regulation (Note 6)LM1117-ADJ
I OUT =10mA,1.5V ≤V IN -V OUT ≤13.75V 0.0350.2%LM1117-2.85
I OUT =0mA,4.25V ≤V IN ≤10V 16mV LM1117-3.3
I OUT =0mA,4.75V ≤V IN ≤15V 16mV LM1117-5.0
I OUT =0mA,6.5V ≤V IN ≤15V
110mV ?V OUT
Load Regulation (Note 6)LM1117-ADJ
V IN -V OUT =3V,10≤I OUT ≤800mA 0.20.4%LM1117-2.85
V IN =4.25V,0≤I OUT ≤800mA 110mV LM1117-3.3
V IN =4.75V,0≤I OUT ≤800mA 110mV LM1117-5.0
V IN =6.5V,0≤I OUT ≤800mA
115mV V IN -V OUT
Dropout Voltage (Note 7)I OUT =100mA 1.10 1.20V I OUT =500mA 1.15 1.25V I OUT =800mA
1.20
1.30V I LIMIT Current Limit V IN -V OUT =5V,T J =25?C 800
12001500mA Minimum Load Current (Note 8)
LM1117-ADJ V IN =15V
1.7
5
mA
4
Electrical Characteristics
(Continued)Typicals and limits appearing in normal type apply for T
J
=25?C.Limits appearing in Boldface type apply over the entire junc-tion temperature range for operation,0?C to 125?C.Symbol
Parameter Conditions
Min (Note 5)
Typ (Note 4)
Max
(Note 5)
Units Quiescent Current
LM1117-2.85
V IN ≤10V 510mA LM1117-3.3V IN ≤15V 510mA LM1117-5.0V IN ≤15V
510mA Thermal Regulation T A =25?C,30ms Pulse 0.010.1
%/W Ripple Regulation f RIPPLE =120Hz,V IN -V OUT =3V V RIPPLE =1V PP
60
75dB Adjust Pin Current 60120μA Adjust Pin Current Change
10≤I OUT ≤800mA,1.4V ≤V IN -V OUT ≤10V 0.25μA Temperature Stability 0.5%Long Term Stability T A =125?C,1000Hrs 0.3%RMS Output Noise (%of V OUT ),10Hz ≤f ≤10kHz 0.003%Thermal Resistance Junction-to-Case 3-Lead SOT-2233,5 -Lead TO-2203,5 -Lead TO-25215.0
3.010?C/W ?C/W ?C/W Thermal Resistance Junction-to-Ambient (No heat sink;No air flow)
3-Lead SOT-2233,5 -Lead TO-220
3,5 -Lead TO-252(Note 9)1367992
?C/W ?C/W ?C/W
Note 1:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.Operating Ratings indicate conditions for which the device is in-tended to be functional,but specific performance is not guaranteed.For guaranteed specifications and the test conditions,see the Electrical Characteristics.Note 2:The maximum power dissipation is a function of T J(max),θJA ,and T A .The maximum allowable power dissipation at any ambient temperature is P D =(T J -(max)–T A )/θJA .All numbers apply for packages soldered directly into a PC board.
Note 3:For testing purposes,ESD was applied using human body model,1.5k ?in series with 100pF.Note 4:Typical Values represent the most likely parametric norm.Note 5:All limits are guaranteed by testing or statistical analysis.
Note 6:Load and line regulation are measured at constant junction room temperature.
Note 7:The dropout voltage is the input/output differential at which the circuit ceases to regulate against further reduction in input voltage.It is measured when the output voltage has dropped 100mV from the nominal value obtained at V IN =V OUT +1.5V.Note 8:The minimum output current required to maintain regulation.Note 9:Minimum pad size of 0.038in 2
5
Typical Performance
Characteristics
Dropout
Voltage (V IN -V
OUT )
DS100919-22Short-Circuit Current
DS100919-23
Load Regulation LM1117-ADJ Ripple Rejection
LM1117-ADJ Ripple Rejection vs.Current Temperature Stability
6
Typical Performance Characteristics
(Continued)
LM1117-2.85
Load Transient Response
LM1117-5.0Load Transient Response LM1117-2.85Line Transient Response
LM1117-5.0Line Transient Response
7
Adjust Pin Current
APPLICATION NOTE
1.0External Capacitors/Stability
1.1Input Bypass Capacitor
An input capacitor is recommended.A 10μF tantalum on the input is a suitable input bypassing for almost all applications.1.2Adjust Terminal Bypass Capacitor
The adjust terminal can be bypassed to ground with a by-pass capacitor (C ADJ )to improve ripple rejection.This by-pass capacitor prevents ripple from being amplified as the output voltage is increased.At any ripple frequency,the im-pedance of the C ADJ should be less than R1to prevent the
ripple from being amplified:(2π*f RIPPLE *C ADJ ) The R1is the resistor between the output and the adjust pin.Its value is normally in the range of 100-200?.For example,with R1=124?and f RIPPLE =120Hz,the C ADJ should be >11μF. 1.3Output Capacitor The output capacitor is critical in maintaining regulator stabil-ity,and must meet the required conditions for both minimum amount of capacitance and ESR (Equivalent Series Resis-tance).The minimum output capacitance required by the LM1117is 10μF,if a tantalum capacitor is used.Any increase of the output capacitance will merely improve the loop stabil-ity and transient response.The ESR of the output capacitor should be less than 0.5?.In the case of the adjustable regu-lator,when the C ADJ is used,a larger output capacitance (22μf tantalum)is required. 2.0Output Voltage The LM1117adjustable version develops a 1.25V reference voltage,V REF ,between the output and the adjust terminal.As shown in Figure 1,this voltage is applied across resistor R1to generate a constant current I1.The current I ADJ from the adjust terminal could introduce error to the output.But since it is very small (60μA)compared with the I1and very constant with line and load changes,the error can be ig-nored.The constant current I1then flows through the output set resistor R2and sets the output voltage to the desired level. For fixed voltage devices,R1and R2are integrated inside the devices. 3.0Load Regulation The LM1117regulates the voltage that appears between its output and ground pins,or between its output and adjust pins.In some cases,line resistances can introduce errors to the voltage across the load.To obtain the best load regula-tion,a few precautions are needed. Figure 2,shows a typical application using a fixed output regulator.The Rt1and Rt2are the line resistances.It is ob-vious that the V LOAD is less than the V OUT by the sum of the voltage drops along the line resistances.In this case,the load regulation seen at the R LOAD would be degraded from the data sheet specification.To improve this,the load should be tied directly to the output terminal on the positive side and directly tied to the ground terminal on the negative side. When the adjustable regulator is used (Figure 3),the best performance is obtained with the positive side of the resistor R1tied directly to the output terminal of the regulator rather than near the load.This eliminates line drops from appearing effectively in series with the reference and degrading regula-tion.For example,a 5V regulator with 0.05?resistance be-tween the regulator and load will have a load regulation due to line resistance of 0.05?x I L .If R1(=125?)is connected near the load,the effective line resistance will be 0.05?(1+R2/R1)or in this case,it is 4times worse.In addition,the ground side of the resistor R2can be returned near the ground of the load to provide remote ground sensing and im-prove load regulation. 4.0Protection Diodes Under normal operation,the LM1117regulators do not need any protection diode.With the adjustable device,the internal resistance between the adjust and output terminals limits the current.No diode is needed to divert the current around the regulator even with capacitor on the adjust terminal.The ad-just pin can take a transient signal of ±25V with respect to the output voltage without damaging the device. When a output capacitor is connected to a regulator and the input is shorted to ground,the output capacitor will discharge FIGURE 1.Basic Adjustable Regulator FIGURE 2.Typical Application using Fixed Output Regulator FIGURE 3.Best Load Regulation using Adjustable Output Regulator 8 APPLICATION NOTE (Continued) into the output of the regulator.The discharge current de-pends on the value of the capacitor,the output voltage of the regulator,and rate of decrease of V IN .In the LM1117regu-lators,the internal diode between the output and input pins can withstand microsecond surge currents of 10A to 20A.With an extremely large output capacitor (≥1000μF),and with input instantaneously shorted to ground,the regulator could be damaged. In this case,an external diode is recommended between the output and input pins to protect the regulator,as shown in Figure 4. 5.0Heatsink Requirements When an integrated circuit operates with an appreciable cur-rent,its junction temperature is elevated.It is important to quantify its thermal limits in order to achieve acceptable per-formance and reliability.This limit is determined by summing the individual parts consisting of a series of temperature rises from the semiconductor junction to the operating envi-ronment.A one-dimensional steady-state model of conduc-tion heat transfer is demonstrated in Figure 5.The heat gen-erated at the device junction flows through the die to the die attach pad,through the lead frame to the surrounding case material,to the printed circuit board,and eventually to the ambient environment.Below is a list of variables that may af-fect the thermal resistance and in turn the need for a heat-sink. R θJC (Component Vari-ables)R θCA (Application Vari-ables)Leadframe Size &Material Mounting Pad Size,Material,&Location No.of Conduction Pins Placement of Mounting Pad Die Size PCB Size &Material Die Attach Material Traces Length &Width Molding Compound Size and Material Adjacent Heat Sources Volume of Air Ambient Temperatue Shape of Mounting Pad The LM1117regulators have internal thermal shutdown to protect the device from over-heating.Under all possible op-erating conditions,the junction temperature of the LM1117must be within the range of 0?C to 125?C.A heatsink may be required depending on the maximum power dissipation and maximum ambient temperature of the application.To deter-mine if a heatsink is needed,the power dissipated by the regulator,P D ,must be calculated:I IN =I L +I G P D =(V IN -V OUT )I L +V IN I G Figure 6shows the voltages and currents which are present in the circuit. FIGURE 4.Regulator with Protection Diode FIGURE 5.Cross-sectional view of Integrated Circuit Mounted on a printed circuit board.Note that the case temperature is measured at the point where the leads contact with the mounting pad surface FIGURE 6.Power Dissipation Diagram 9 APPLICATION NOTE (Continued) The next parameter which must be calculated is the maxi-mum allowable temperature rise,T R (max): T R (max)=T J (max)-T A (max) where T J (max)is the maximum allowable junction tempera-ture (125?C),and T A (max)is the maximum ambient tem-perature which will be encountered in the https://www.sodocs.net/doc/c22875835.html,ing the calculated values for T R (max)and P D ,the maxi-mum allowable value for the junction-to-ambient thermal re-sistance (θJA )can be calculated: θJA =T R (max)/P D If the maximum allowable value for θJA is found to be ≥136?C/W for SOT-223package or ≥79?C/W for TO-220package or ≥92?C/W for TO-252package,no heatsink is needed since the package alone will dissipate enough heat to satisfy these requirements.If the calculated value for θJA falls below these limits,a heatsink is required. As a design aid,Table 1shows the value of the θJA of SOT-223and TO-252for different heatsink area.The copper pat-terns that we used to measure these θJA s are shown at the end of the Application Notes Section.Figure 7and Figure 8reflects the same test results as what are in the Table 1Figure 9and Figure 10shows the maximum allowable power dissipation vs.ambient temperature for the SOT-223and TO-252device.Figures Figure 11and Figure 12shows the maximum allowable power dissipation vs.copper area (in 2)for the SOT-223and TO-252devices.Please see AN1028for power enhancement techniques to be used with SOT-223and TO-252packages. TABLE 1.θJA Different Heatsink Area Layout Copper Area Thermal Resistance Top Side (in 2 )* Bottom Side (in 2 ) (θJA ,?C/W)SOT-223 (θJA ,?C/W)TO-252 10.0123013610320.0660*******.30846040.530755450.76069526106647700.211584800.49870900.689631000.8825711017957120.0660.0661*******.1750.1759372140.2840.2848361150.3920.392755516 0.5 0.5 70 53 *Tab of device attached to topside copper FIGURE 7.θJA vs.1oz Copper Area for SOT-223 FIGURE 8.θJA vs.2oz Copper Area for TO-252 10 APPLICATION NOTE (Continued) FIGURE 9.Maximum Allowable Power Dissipation vs. Ambient Temperature for SOT-223FIGURE 10.Maximum Allowable Power Dissipation vs. Ambient Temperature for TO-252 FIGURE 11.Maximum Allowable Power Dissipation vs. 1oz Copper Area for SOT-223 FIGURE 12.Maximum Allowable Power Dissipation vs. 2oz Copper Area for TO-25211 Typical Application Circuits Adjusting Output of Fixed Regulators Regulator with Reference 1.25V to 10V Adjustable Regulator with Improved Ripple Rejection 5V Logic Regulator with Electronic Shutdown* Battery Backed-Up Regulated Supply 12 Low Dropout Negative Supply Battery Backed-Up Regulated Supply 13 Physical Dimensions inches (millimeters)unless otherwise noted (Continued) 3-Lead TO-220Package Physical Dimensions inches (millimeters)unless otherwise noted (Continued) 3-Lead TO-252 Package 3-Lead SOT-223 Package 1 4 Physical Dimensions inches (millimeters)unless otherwise noted