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LM1117 800mA Low-Dropout Linear Regulator
February 2000
LM1117 800mA Low-Dropout Linear Regulator
General Description
The LM1117 is 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 LM1117 is available in an adjustable version, which can set the output voltage from 1.25V to 13.8V with only two external resistors. In addition, it is also available in five fixed voltages, 1.8V, 2.5V, 2.85V, 3.3V, and 5V. The LM1117 offers current limiting and thermal shutdown. Its circuit includes a zener trimmed bandgap reference to assure output voltage accuracy to within ± 1%. The LM1117 series is available in SOT-223, TO-220, and TO-252 D-PAK packages. A minimum of 10µF tantalum capacitor is required at the output to improve the transient response and stability.
Features
n Available in 1.8V, 2.5V, 2.85V, 3.3V, 5V, and Adjustable Versions n Space Saving SOT-223 Package 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 n n n n 2.85V Model for SCSI-2 Active Termination Post Regulator for Switching DC/DC Converter High Efficiency Linear Regulators Battery Charger Battery Powered Instrumentation
Typical Application
Active Terminator for SCSI-2 Bus
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Fixed Output Regulator
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© 2000 National Semiconductor Corporation
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LM1117
Ordering Information
Package 3-lead SOT-223 Temperature Range 0°C to +125°C LM1117MPX-ADJ LM1117MPX-1.8 * LM1117MPX-2.5 LM1117MPX-2.85 LM1117MPX-3.3 LM1117MPX-5.0 3-lead TO-220 LM1117T-ADJ LM1117T-2.85 LM1117T-3.3 LM1117T-5.0 3-lead TO-252 LM1117DTX-ADJ LM1117DTX-1.8 * LM1117DTX-2.5 LM1117DTX-2.85 LM1117DTX-3.3 LM1117DTX-5.0
Note: * Contact factory for availability.
Packaging Marking N03A N12A N13A N04A N05A N06A LM1117T-ADJ LM1117T-2.85 LM1117T-3.3 LM1117T-5.0 LM1117DT-ADJ LM1117DT-1.8 LM1117DT-2.5 LM1117DT-2.85 LM1117DT-3.3 LM1117DT-5.0
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NSC Drawing MA04A
T03B
TD03B
Block Diagram
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LM1117
Connection Diagrams
SOT-223
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Top View TO-220
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Top View TO-252
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Top View
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LM1117
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 (VIN to GND) LM1117-ADJ, LM1117-1.8, LM1117-2.5, LM1117-3.3, LM1117-5.0 Power Dissipation (Note 2) Junction Temperature (TJ) (Note 2) Storage Temperature Range Lead Temperature
TO-220 (T) Package SOT-223 (IMP) Package ESD Tolerance (Note 3)
260°C, 10 sec 260°C, 4 sec 2000V
Operating Ratings (Note 1)
Input Voltage (VIN to GND) 20V Internally Limited 150°C -65°C to 150°C LM1117-ADJ, LM1117-1.8, LM1117-2.5, LM1117-3.3, LM1117-5.0 LM1117-2.85 Junction Temperature Range (TJ)(Note 2) 15V 10V 0°C to 125°C
Electrical Characteristics
Typicals and limits appearing in normal type apply for TJ = 25°C. Limits appearing in Boldface type apply over the entire junction temperature range for operation, 0°C to 125°C. Symbol VREF Parameter Reference Voltage Conditions LM1117-ADJ IOUT = 10mA, VIN-VOUT = 2V, TJ = 25°C 10mA IOUT 800mA, 1.4V VIN-VOUT 10V LM1117-1.8 IOUT = 10mA, VIN = 3.8V, TJ = 25°C 0 IOUT 800mA, 3.2V VIN 10V LM1117-2.5 IOUT = 10mA, VIN = 4.5V, TJ = 25°C 0 IOUT 800mA, 3.9V VIN 10V LM1117-2.85 IOUT = 10mA, VIN = 4.85V, TJ = 25°C 0 IOUT 800mA, 4.25V VIN 10V 0 IOUT 500mA, VIN = 4.10V LM1117-3.3 IOUT = 10mA, VIN = 5V TJ = 25°C 0 IOUT 800mA, 4.75V VIN 10V LM1117-5.0 IOUT = 10mA, VIN = 7V, TJ = 25°C 0 IOUT 800mA, 6.5V VIN 12V VOUT Line Regulation (Note 6) LM1117-ADJ IOUT = 10mA, 1.5V VIN-VOUT 13.75V LM1117-1.8 IOUT = 0mA, 3.2V VIN 10V LM1117-2.5 IOUT = 0mA, 3.9V VIN 10V LM1117-2.85 IOUT = 0mA, 4.25V VIN 10V LM1117-3.3 IOUT = 0mA, 4.75V VIN 15V LM1117-5.0 IOUT = 0mA, 6.5V VIN 15V Min (Note 5) 1.238 1.225 Typ (Note 4) 1.250 1.250 Max (Note 5) 1.262 1.270 Units
V V
VOUT
Output Voltage
1.782 1.746 2.475 2.450 2.820 2.790 2.790 3.267 3.235 4.950 4.900
1.800 1.800 2.500 2.500 2.850 2.850 2.850 3.300 3.300 5.000 5.000 0.035 1 1
1.818 1.854 2.525 2.550 2.880 2.910 2.910 3.333 3.365 5.050 5.100 0.2 6 6
V V V V V V V V V V V % mV mV
1 1 1
6 6 10
mV mV mV
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LM1117
Electrical Characteristics
(Continued)
Typicals and limits appearing in normal type apply for TJ = 25°C. Limits appearing in Boldface type apply over the entire junction temperature range for operation, 0°C to 125°C. Symbol VOUT Parameter Load Regulation (Note 6) Conditions LM1117-ADJ VIN-VOUT = 3V, 10 IOUT 800mA LM1117-1.8 VIN = 3.2V, 0 IOUT 800mA LM1117-2.5 VIN = 3.9V, 0 IOUT 800mA LM1117-2.85 VIN = 4.25V, 0 IOUT 800mA LM1117-3.3 VIN = 4.75V, 0 IOUT 800mA LM1117-5.0 VIN = 6.5V, 0 IOUT 800mA VIN-V OUT Dropout Voltage (Note 7) Current Limit Minimum Load Current (Note 8) Quiescent Current IOUT = 100mA IOUT = 500mA IOUT = 800mA ILIMIT VIN-VOUT = 5V, TJ = 25°C LM1117-ADJ VIN = 15V LM1117-1.8 VIN 15V LM1117-2.5 VIN 15V LM1117-2.85 VIN 10V LM1117-3.3 VIN 15V LM1117-5.0 VIN 15V Thermal Regulation Ripple Regulation Adjust Pin Current Adjust Pin Current Change Temperature Stability Long Term Stability RMS Output Noise Thermal Resistance Junction-to-Case Thermal Resistance Junction-to-Ambient (No heat sink; No air flow) TA = 125°C, 1000Hrs (% of VOUT), 10Hz f 10kHz 3-Lead SOT-223 3-Lead TO-220 3-Lead TO-252 3-Lead SOT-223 3-Lead TO-220 3-Lead TO-252 (Note 9) 10 IOUT 800mA, 1.4V VIN-VOUT 10V TA = 25°C, 30ms Pulse fRIPPLE =1 20Hz, VIN-VOUT = 3V VRIPPLE = 1VPP 60 800 Min (Note 5) Typ (Note 4) 0.2 1 1 Max (Note 5) 0.4 10 10 Units
% mV mV
1 1 1 1.10 1.15 1.20 1200 1.7 5 5
10 10 15 1.20 1.25 1.30 1500 5 10 10
mV mV mV V V V mA mA mA mA
5 5 5 0.01 75 60 0.2 0.5 0.3 0.003 15.0 3.0 10 136 79 92
10 10 10 0.1
mA mA mA %/W dB
120 5
µA µA % % % °C/W °C/W °C/W °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 intended 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 TJ(max) , JA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(max)TA)/JA. 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.
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LM1117
Electrical Characteristics
(Continued)
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 VIN = VOUT +1.5V. Note 8: The minimum output current required to maintain regulation. Note 9: Minimum pad size of 0.038in2
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LM1117
Typical Performance Characteristics
Dropout Voltage (VIN-V
OUT)
Short-Circuit Current
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Load Regulation
LM1117-ADJ Ripple Rejection
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LM1117-ADJ Ripple Rejection vs. Current
Temperature Stability
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LM1117
Typical Performance Characteristics
Adjust Pin Current
(Continued) LM1117-2.85 Load Transient Response
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LM1117-5.0 Load Transient Response
LM1117-2.85 Line Transient Response
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LM1117-5.0 Line Transient Response
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LM1117
APPLICATION NOTE
1.0 External Capacitors/Stability 1.1 Input Bypass Capacitor An input capacitor is recommended. A 10µF tantalum on the input is a suitable input bypassing for almost all applications. 1.2 Adjust Terminal Bypass Capacitor The adjust terminal can be bypassed to ground with a pass capacitor (CADJ) to improve ripple rejection. This pass capacitor prevents ripple from being amplified as output voltage is increased. At any ripple frequency, the pedance of the CADJ should be less than R1 to prevent ripple from being amplified: (2*fRIPPLE*CADJ) < R1 bybythe imthe
Figure 2, shows a typical application using a fixed output regulator. The Rt1 and Rt2 are the line resistances. It is obvious that the VLOAD is less than the VOUT by the sum of the voltage drops along the line resistances. In this case, the load regulation seen at the RLOAD 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.
The R1 is 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 fRIPPLE=120Hz, the CADJ should be > 11µF. 1.3 Output Capacitor The output capacitor is critical in maintaining regulator stability, and must meet the required conditions for both minimum amount of capacitance and ESR (Equivalent Series Resistance). The minimum output capacitance required by the LM1117 is 10µF, if a tantalum capacitor is used. Any increase of the output capacitance will merely improve the loop stability and transient response. The ESR of the output capacitor should be less than 0.5. In the case of the adjustable regulator, when the CADJ is used, a larger output capacitance (22µf tantalum) is required. 2.0 Output Voltage The LM1117 adjustable version develops a 1.25V reference voltage, VREF, between the output and the adjust terminal. As shown in Figure 1, this voltage is applied across resistor R1 to generate a constant current I1. The current IADJ from the adjust terminal could introduce error to the output. But since it is very small (60µA) compared with the I1 and very constant with line and load changes, the error can be ignored. The constant current I1 then flows through the output set resistor R2 and sets the output voltage to the desired level. For fixed voltage devices, R1 and R2 are integrated inside the devices.
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FIGURE 2. Typical Application using Fixed Output Regulator When the adjustable regulator is used (Figure 3), the best performance is obtained with the positive side of the resistor R1 tied 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 regulation. For example, a 5V regulator with 0.05 resistance between the regulator and load will have a load regulation due to line resistance of 0.05 x IL. 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 4 times worse. In addition, the ground side of the resistor R2 can be returned near the ground of the load to provide remote ground sensing and improve load regulation.
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FIGURE 3. Best Load Regulation using Adjustable Output Regulator 4.0 Protection Diodes Under normal operation, the LM1117 regulators 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 adjust 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
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FIGURE 1. Basic Adjustable Regulator 3.0 Load Regulation The LM1117 regulates 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 regulation, a few precautions are needed.
LM1117
APPLICATION NOTE
(Continued)
into the output of the regulator. The discharge current depends on the value of the capacitor, the output voltage of the regulator, and rate of decrease of VIN. In the LM1117 regulators, the internal diode between the output and input pins can withstand microsecond surge currents of 10A to 20A. With an extremely large output capacitor (1000 µF), 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.
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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 The LM1117 regulators have internal thermal shutdown to protect the device from over-heating. Under all possible operating conditions, the junction temperature of the LM1117 must 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 determine if a heatsink is needed, the power dissipated by the regulator, PD , must be calculated: IIN = IL + IG PD = (VIN-VOUT)I L + VINIG Figure 6 shows the voltages and currents which are present in the circuit.
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FIGURE 4. Regulator with Protection Diode 5.0 Heatsink Requirements When an integrated circuit operates with an appreciable current, its junction temperature is elevated. It is important to quantify its thermal limits in order to achieve acceptable performance 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 environment. A one-dimensional steady-state model of conduction heat transfer is demonstrated in Figure 5. The heat generated 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 affect the thermal resistance and in turn the need for a heatsink. RJC(Component Variables) Leadframe Size & Material No. of Conduction Pins Die Size Die Attach Material Molding Compound Size and Material RCA (Application Variables) Mounting Pad Size, Material, & Location Placement of Mounting Pad PCB Size & Material Traces Length & Width Adjacent Heat Sources Volume of Air Ambient Temperatue Shape of Mounting Pad
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FIGURE 6. Power Dissipation Diagram
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LM1117
APPLICATION NOTE
TR(max)=TJ(max)-TA(max)
(Continued)
The next parameter which must be calculated is the maximum allowable temperature rise, TR(max): where TJ(max) is the maximum allowable junction temperature (125°C), and TA(max) is the maximum ambient temperature which will be encountered in the application. Using the calculated values for TR(max) and PD, the maximum allowable value for the junction-to-ambient thermal resistance (JA) can be calculated: JA = TR(max)/PD If the maximum allowable value for JA is found to be 136°C/W for SOT-223 package or 79°C/W for TO-220 package or 92°C/W for TO-252 package, no heatsink is
needed since the package alone will dissipate enough heat to satisfy these requirements. If the calculated value for JA falls below these limits, a heatsink is required. As a design aid, Table 1 shows the value of the JA of SOT223 and TO-252 for different heatsink area. The copper patterns that we used to measure these JAs are shown at the end of the Application Notes Section. Figure 7 and Figure 8 reflects the same test results as what are in the Table 1 Figure 9 and Figure 10 shows the maximum allowable power dissipation vs. ambient temperature for the SOT-223 and TO-252 device. Figures Figure 11 and Figure 12 shows the maximum allowable power dissipation vs. copper area (in2) for the SOT-223 and TO-252 devices. Please see AN1028 for power enhancement techniques to be used with SOT-223 and TO-252 packages.
TABLE 1. JA Different Heatsink Area Layout
2
Copper Area Top Side (in )* Bottom Side (in ) 0 0 0 0 0 0 0.2 0.4 0.6 0.8 1 0.066 0.175 0.284 0.392 0.5
2
Thermal Resistance (JA,°C/W) SOT-223 136 123 84 75 69 66 115 98 89 82 79 125 93 83 75 70 (JA,°C/W) TO-252 103 87 60 54 52 47 84 70 63 57 57 89 72 61 55 53
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
0.0123 0.066 0.3 0.53 0.76 1 0 0 0 0 0 0.066 0.175 0.284 0.392 0.5
*Tab of device attached to topside copper
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LM1117
APPLICATION NOTE
(Continued)
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FIGURE 10. Maximum Allowable Power Dissipation vs. Ambient Temperature for TO-252
FIGURE 7. JA vs. 1oz Copper Area for SOT-223
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FIGURE 8. JA vs. 2oz Copper Area for TO-252
FIGURE 11. Maximum Allowable Power Dissipation vs. 1oz Copper Area for SOT-223
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FIGURE 9. Maximum Allowable Power Dissipation vs. Ambient Temperature for SOT-223
FIGURE 12. Maximum Allowable Power Dissipation vs. 2oz Copper Area for TO-252
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LM1117
APPLICATION NOTE
(Continued)
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FIGURE 13. Top View of the Thermal Test Pattern in Actual Scale
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LM1117
APPLICATION NOTE
(Continued)
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FIGURE 14. Bottom View of the Thermal Test Pattern in Actual Scale
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LM1117
Typical Application Circuits
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Adjusting Output of Fixed Regulators
Regulator with Reference
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5V Logic Regulator with Electronic Shutdown*
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1.25V to 10V Adjustable Regulator with Improved Ripple Rejection
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Battery Backed-Up Regulated Supply
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LM1117
Typical Application Circuits
(Continued)
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Low Dropout Negative Supply
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LM1117
Physical Dimensions
inches (millimeters) unless otherwise noted
3-Lead SOT-223 Package Order Number LM1117MPX-ADJ, LM1117MPX-1.8, LM1117MPX-2.5, LM1117MPX-2.85, LM1117MPX-3.3, or LM1117MPX-5.0 NSC Package Number MA04A
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LM1117
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
3-Lead TO-220 Package Order Number LM1117T-ADJ, LM1117T-2.85, LM1117T-3.3, or LM1117T-5.0 NSC Package Number T03B
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LM1117 800mA Low-Dropout Linear Regulator
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
3-Lead TO-252 Package Order Number LM1117DTX-ADJ, LM1117DTX-1.8, LM1117DTX-2.5, LM1117DTX-2.85, LM1117DTX-3.3, or LM1117DTX-5.0 NSC Package Number TD03B
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