( )
OUT ADJ
R
V = 1.25 V I R
R2
2
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intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM317A
SNVSAC2A –MARCH 2015–REVISED JUNE 2020
LM317A 1% Accurate 1.5A Adjustable Voltage Regulator
1
1 Features
1• For a newer drop-in alternative, see the LM317
• Typical 0.005%/V line regulation
• 1% output voltage tolerance
• 1.5-A output current
• Adjustable output down to 1.25 V
• Input-output differential up to 40 V
• Current limit constant with temperature
• No output capacitor required
• Short-circuit protected output
•−40°C to 125°C operating temperature range
2 Applications
• Automotive LED lighting
• Battery chargers
• Post regulation for switching supplies
• Constant-current regulator
• Microprocessor supplies
Typical Application
*Needed if device is more than 6 inches from filter
capacitors.
†Optional—improves transient response
††
3 Description
The LM317A adjustable 3-terminal, positive-voltage
regulators are capable of supplying current in excess
of 1.5 A over a 1.25-V to 37-V output range and
provide 1% output-voltage accuracy. Both line
regulation and load regulation are better achieved
with the LM317A device than with standard fixed
regulators.
The LM317A offers full overload protection such as
over current, thermal-overload protection, and safe-
area protection. All overload protection circuitry
remains fully functional even if the adjustment
terminal is disconnected.
Typically, no capacitors are needed unless the device
is situated more than 6 inches from the input filter
capacitors, in which case an input bypass is needed.
An optional output capacitor can be added to improve
transient response and can be replaced with a
ceramic and appropriate ESR. The adjustment
terminal can be bypassed to achieve very high ripple-
rejection ratios that are difficult to achieve with
standard 3-terminal regulators.
Because the LM317A regulator is floating and detects
only the input-to-output differential voltage, supplies
of several hundred volts can be regulated as long as
the maximum input-to-output differential is not
exceeded. Exceeding the maximum input-to-output
deferential will result in short-circuiting the output. By
connecting a fixed resistor between the adjustment
pin and output, the LM317A can be also used as a
precision current regulator.
For applications requiring greater output current, see
the LM150 series (3A) and LM138 series (5A) data
sheets. For the negative complement, see the LM137
series data sheet.
Device Information(1)
PART
NUMBER PACKAGE BODY SIZE (NOM)
LM317A
TO-220 (3) 14.986 mm × 10.16 mm
SOT-223 (4) 6.50 mm × 3.50 mm
TO (3) 8.255 mm × 8.255 mm
TO-252 (3) 6.58 mm × 6.10 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
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Table of Contents
1 Features.................................................................. 1
2 Applications ........................................................... 1
3 Description............................................................. 1
4 Revision History..................................................... 2
5 Device Comparison Table..................................... 3
6 Pin Configuration and Functions......................... 4
7 Specifications......................................................... 5
7.1 Absolute Maximum Ratings ...................................... 5
7.2 ESD Ratings.............................................................. 5
7.3 Recommended Operating Conditions....................... 5
7.4 Thermal Information.................................................. 5
7.5 Electrical Characteristics........................................... 6
7.6 Typical Characteristics.............................................. 7
8 Detailed Description............................................ 10
8.1 Overview................................................................. 10
8.2 Functional Block Diagram....................................... 11
8.3 Feature Description................................................. 12
8.4 Device Functional Modes........................................ 12
9 Application and Implementation ........................ 14
9.1 Application Information............................................ 14
9.2 Typical Applications ................................................ 14
10 Power Supply Recommendations ..................... 25
11 Layout................................................................... 25
11.1 Layout Guidelines ................................................. 25
11.2 Layout Examples................................................... 30
12 Device and Documentation Support................. 32
12.1 Documentation Support ........................................ 32
12.2 Receiving Notification of Documentation Updates 32
12.3 Support Resources ............................................... 32
12.4 Trademarks........................................................... 32
12.5 Electrostatic Discharge Caution............................ 32
12.6 Glossary................................................................ 32
13 Mechanical, Packaging, and Orderable
Information........................................................... 32
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Original (October 2015) to Revision A Page
• Added alternative device Features bullet ............................................................................................................................... 1
• Changed Device Comparison Table ...................................................................................................................................... 3
• Changed Related Documentation section............................................................................................................................ 32
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5 Device Comparison Table
IOUT PARAMETER LM317 LM317-N LM317A LM317HV UNIT
1.5 A
Input voltage range 4.25 - 40 4.25 - 40 4.25 - 40 4.25 - 60 V
Load regulation accuracy 1.5 1.5 1 1.5 %
PSRR (120 Hz) 64 80 80 65 dB
Recommended operating temperature 0 to 125 0 to 125 –40 to 125 0 to 125 °C
TO-220 (NDE) TJA 23.5 23.2 23.3 23 °C/W
TO-200 (KCT) TJA 37.9 N/A N/A N/A °C/W
TO-252 TJA N/A 54 54 N/A °C/W
TO-263 TJA 38 41 N/A N/A °C/W
SOT-223 TJA 66.8 59.6 59.6 N/A °C/W
TO-92 TJA N/A 186 186 N/A °C/W
0.5 A
LM317M
Input voltage range 3.75 - 40 V
Load regulation accuracy 1.5 %
PSRR (120 Hz) 80 dB
Recommended operating temperature -40 - 125 °C
SOT-223 TJA 60.2 °C/W
TO-252 TJA 56.9 °C/W
0.1 A
LM317L LM317L-N
Input voltage range 3.75 - 40 4.25 - 40 V
Load regulation accuracy 1 1.5 %
PSRR (120 Hz) 62 80 dB
Recommended operating temperature –40 to 125 –40 to 125 °C
SOT-23 TJA 167.8 N/A °C/W
SO-8 TJA N/A 165 °C/W
DSBGA TJA N/A 290 °C/W
TO-92 TJA N/A 180 °C/W
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6 Pin Configuration and Functions
Metal Can NDT Package
3-Pin TO
Bottom View
CASE IS OUTPUT
Plastic NDE Package
3-Pin TO-220
Front View
Surface-Mount DCY Package
4-Pin SOT-223
Top View
Surface-Mount NDP Package
4-Pin TO-252
Front View
Pin Functions
PIN I/O DESCRIPTION
NAME TO-220 SOT-223 TO-252 TO
ADJ 1 1 1 2 — Adjust pin
VIN 3 3 3 1 I Input voltage pin for the regulator
VOUT 2, TAB 2, 4 2, TAB 3, CASE O Output voltage pin for the regulator
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(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)(1)(2)
MIN MAX UNIT
Power dissipation Internally Limited
Input-output voltage differential −0.3 40 V
Storage temperature, Tstg −65 150 °C
(1) Manufacturing with less than 500-V HBM is possible with the necessary precautions. Pins listed as ±3000 V may actually have higher
performance.
7.2 ESD Ratings VALUE UNIT
V(ESD) Electrostatic discharge Human body model (HBM)(1) ±3000 V
7.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) MIN MAX UNIT
Operating temperature −40 125 °C
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC package thermal metrics application
report.
(2) When surface mount packages are used (SOT-223, TO-252), the junction to ambient thermal resistance can be reduced by increasing
the PCB copper area that is thermally connected to the package. See Heatsink Requirements for heatsink techniques.
(3) No heatsink.
7.4 Thermal Information
THERMAL METRIC(1)(2)
LM317A
UNIT
NDE
(TO-220) DCY
(SOT-223) NDT
(TO) NDP
(TO-252)
3 PINS 4 PINS 3 PINS 3 PINS
RθJA Junction-to-ambient thermal resistance 23.3 59.6 186(3) 54.0 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 16.2 39.3 21 51.3 °C/W
RθJB Junction-to-board thermal resistance 4.9 8.4 — 28.6 °C/W
ψJT Junction-to-top characterization parameter 2.7 1.8 — 3.9 °C/W
ψJB Junction-to-board characterization parameter 4.9 8.3 — 28.1 °C/W
RθJC(bot) Junction-to-case (bottom) thermal resistance 1.1 — — 0.9 °C/W
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(1) IMAX = 1.5 A for the NDE (TO-220). IMAX = 1.0 A for the DCY (SOT-223) package.
IMAX = 0.5 A for the NDT (TO) and NDP (TO-252) packages. Device power dissipation (PD) is limited by ambient temperature (TA),
device maximum junction temperature (TJ), and package thermal resistance (θJA). The maximum allowable power dissipation at any
temperature is : PD(MAX) = ((TJ(MAX) – TA) / θJA). All minimum and maximum limits are ensured to TI's Average Outgoing Quality Level
(AOQL).
(2) Regulation is measured at a constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to
heating effects are covered under the specifications for thermal regulation.
7.5 Electrical Characteristics
Some specifications apply over full operating temperature range as noted. Unless otherwise specified, TJ= 25°C, VIN −VOUT
= 5 V, and IOUT = 10 mA.(1)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
Reference voltage
TJ= 25°C 1.238 1.250 1.262 V
3 V ≤(VIN −VOUT)≤40 V,
10 mA ≤IOUT ≤IMAX(1)
over full operating temperature range 1.225 1.250 1.270 V
Line regulation 3 V ≤(VIN −VOUT)≤40 V(2) TJ= 25°C 0.005 0.01 %/V
over full operating
temperature range 0.01 0.02
Load regulation 10 mA ≤IOUT ≤IMAX(1) (2) TJ= 25°C 0.1% 0.5%
over full operating
temperature range 0.3% 1%
Thermal regulation 20-ms pulse 0.04 0.07 %/W
Adjustment pin current over full operating temperature range 50 100 μA
Adjustment pin current change 10 mA ≤IOUT ≤IMAX(1)
3 V ≤(VIN −VOUT)≤40 V
(over full operating temperature range) 0.2 5 μA
Temperature stability TMIN ≤TJ≤TMAX, over full operating temperature range 1%
Minimum load current (VIN −VOUT) = 40 V
over full operating temperature range 3.5 10 mA
Current limit
(VIN −VOUT)≤15 V
SOT-223, TO-220
Packages, over full
operating temperature
range 1.5 2.2 3.4
A
TO, TO-252 Packages,
over full operating
temperature range 0.5 0.8 1.8
(VIN −VOUT) = 40 V SOT-223, TO-220
Packages 0.15 0.40 A
TO, TO-252 Packages 0.075 0.20
RMS output noise, % of VOUT 10 Hz ≤f≤10 kHz 0.003%
Ripple rejection ratio
VOUT = 10 V, f = 120 Hz, CADJ = 0 μF
over full operating temperature range 65 dB
VOUT = 10 V, f = 120 Hz, CADJ = 10 μF
over full operating temperature range 66 80 dB
Long-term stability TJ= 125°C, 1000 hrs 0.3% 1%
NDE PACKAGE
DEVICE
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7.6 Typical Characteristics
output capacitor = 0 μF (unless otherwise noted)
Figure 1. Load Regulation Figure 2. Current Limit
Figure 3. Adjustment Current Figure 4. Dropout Voltage
Figure 5. VOUT vs VIN, VOUT = VREF Figure 6. VOUT vs VIN, VOUT = 5V
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Typical Characteristics (continued)
output capacitor = 0 μF (unless otherwise noted)
Figure 7. Temperature Stability Figure 8. Minimum Operating Current
Figure 9. Ripple Rejection Figure 10. Ripple Rejection
Figure 11. Ripple Rejection Figure 12. Output Impedance
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Typical Characteristics (continued)
output capacitor = 0 μF (unless otherwise noted)
Figure 13. Line Transient Response Figure 14. Load Transient Response
( )
OUT ADJ
R
V = 1.25 V I R
R2
2
1
1
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8 Detailed Description
8.1 Overview
In operation, the LM317A develops a nominal 1.25-V reference voltage, VREF, between the output and
adjustment terminal. The reference voltage is impressed across program resistor R1 and, because the voltage is
constant, a constant current I1then flows through the output set resistor R2 giving an output voltage calculated
by Equation 1:
(1)
Figure 15. Setting the VOUT Voltage
Because the 100-μA current from the adjustment terminal represents an error term, the LM317A was designed to
minimize IADJ and make it very constant with line and load changes. To do this, all quiescent operating current is
returned to the output, establishing a minimum load current requirement. If there is insufficient load on the output,
the output will rise.
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8.3 Feature Description
8.3.1 Load Regulation
The LM317A is capable of providing extremely good load regulation but a few precautions are needed to obtain
maximum performance. The current set resistor, R1, should be connected near the output terminal of the
regulator rather than near the load. If R1 is placed too far from the output terminal, then the increased trace
resistance, RS, will cause an error voltage drop in the adjustment loop and degrade load regulation performance.
Therefore, R1 should be placed as close as possible to the output terminal to minimize RSand maximize load
regulation performance.
Figure 16 shows the effect of the trace resistance, RS, when R1 is placed far from the output terminal of the
regulator. It is clear that RSwill cause an error voltage drop especially during higher current loads, so it is
important to minimize the RStrace resistance by keeping R1 close to the regulator output terminal.
Figure 16. Regulator with Line Resistance in Output Lead
With the TO package, care should be taken to minimize the wire length of the output lead. The ground of R2 can
be returned near the ground of the load to provide remote ground sensing and improve load regulation.
8.4 Device Functional Modes
8.4.1 External Capacitors
An input-bypass capacitor is recommended. A 0.1-μF disc or 1-μF solid tantalum on the input is suitable input
bypassing for almost all applications. The device is more sensitive to the absence of input bypassing when
adjustment or output capacitors are used, but the above values will eliminate the possibility of problems.
The adjustment terminal can be bypassed to ground on the LM317A to improve ripple rejection. This bypass
capacitor prevents ripple from being amplified as the output voltage is increased. With a 10-μF bypass capacitor,
80-dB ripple rejection is obtainable at any output level. Increases over 10 μF do not appreciably improve the
ripple rejection at frequencies above 120 Hz. If the bypass capacitor is used, it is sometimes necessary to
include protection diodes to prevent the capacitor from discharging through internal low current paths and
damaging the device.
In general, the best type of capacitor to use is solid tantalum. Solid tantalum capacitors have low impedance
even at high frequencies. Depending upon capacitor construction, it takes about 25 μF in aluminum electrolytic to
equal 1-μF solid tantalum at high frequencies. Ceramic capacitors are also good at high frequencies. However,
some types have a large decrease in capacitance at frequencies around 0.5 MHz. For this reason, 0.01-μF disc
may seem to work better than a 0.1-μF disc as a bypass.
Although the LM317A is stable with no output capacitors, like any feedback circuit, certain values of external
capacitance can cause excessive ringing. This occurs with values between 500 pF and 5000 pF. A 1-μF solid
tantalum (or 25-μF aluminum electrolytic) on the output swamps this effect and insures stability. Any increase of
the load capacitance larger than 10 μF will merely improve the loop stability and output impedance.
( )
OUT ADJ
R
V = 1.25 V I R
R2
2
1
1
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Device Functional Modes (continued)
8.4.2 Protection Diodes
When external capacitors are used with any IC regulator, it is sometimes necessary to add protection diodes to
prevent the capacitors from discharging through low-current points into the regulator. Most 10-μF capacitors have
low enough internal series resistance to deliver 20-A spikes when shorted. Although the surge is short, there is
enough energy to damage parts of the IC.
When an output capacitor is connected to a regulator and the input is shorted, the output capacitor will discharge
into the output of the regulator. The discharge current depends on the value of the capacitor, the output voltage
of the regulator, and the rate of decrease of VIN. In the LM317A, this discharge path is through a large junction
that is able to sustain 15-A surge with no problem. This is not true of other types of positive regulators. For
output capacitors of 25 μF or less, there is no need to use diodes.
The bypass capacitor on the adjustment terminal can discharge through a low current junction. Discharge occurs
when either the input, or the output, is shorted. Internal to the LM317A is a 50-Ωresistor which limits the peak
discharge current. No protection is needed for output voltages of 25 V or less and 10-μF capacitance. Figure 17
shows an LM317A with protection diodes included for use with outputs greater than 25 V and high values of
output capacitance.
D1 protects against C1
D2 protects against C2
Figure 17. Regulator With Protection Diodes
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The LM317A is a versatile, high-performance, linear regulator with 1% output-voltage accuracy. An output
capacitor can be added to further improve transient response, and the ADJ pin can be bypassed to achieve very
high ripple-rejection ratios. Its functionality can be utilized in many different applications that require high
performance regulation, such as battery chargers, constant-current regulators, and microprocessor supplies.
9.2 Typical Applications
9.2.1 1.25-V to 25-V Adjustable Regulator
The LM317A can be used as a simple, low-dropout regulator to enable a variety of output voltages needed for
demanding applications. By using an adjustable R2 resistor, a variety of output voltages can be made possible
as shown in Figure 18.
NOTE: Full output current not available at high input-output voltages
*Needed if device is more than 6 inches from filter capacitors.
†Optional—improves transient response. Output capacitors in the range of 1 μF to 1000 μF of aluminum or tantalum
electrolytic are commonly used to provide improved output impedance and rejection of transients.
Figure 18. 1.25-V to 25-V Adjustable Regulator
9.2.1.1 Design Requirements
The device component count is very minimal, employing two resistors as part of a voltage-divider circuit and an
output capacitor for load regulation. An input capacitor is needed if the device is more than 6 inches from filter
capacitors. An optional bypass capacitor across R2 can also be used to improve PSRR.
9.2.1.2 Detailed Design Procedure
The output voltage is set based on the selection of the two resistors, R1 and R2, as shown in Figure 18. For
details on capacitor selection, refer to External Capacitors.
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Typical Applications (continued)
9.2.1.3 Application Curve
As shown in Figure 19, VOUT will rise with VIN minus some dropout voltage. This dropout voltage during startup
will vary with ROUT.
Figure 19. VOUT vs VIN, VOUT =5V
9.2.2 5-V Logic Regulator With Electronic Shutdown
Figure 20 shows a variation of the 5-V output regulator application uses the LM317A, along with an NPN
transistor, to provide shutdown control. The NPN will either block or sink the current from the ADJ pin by
responding to the TTL pin logic. When TTL is pulled high, the NPN is on and pulls the ADJ pin to GND, and the
LM317A outputs about 1.25 V. When TTL is pulled low, the NPN is off and the regulator outputs according to the
programmed adjustable voltage.
NOTE: * Min. output ≊1.25 V
Figure 20. 5-V Logic Regulator With Electronic Shutdown
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Typical Applications (continued)
9.2.3 Slow Turnon 15-V Regulator
An application of LM317A includes a PNP transistor with a capacitor to implement slow turnon functionality (see
Figure 21). As VIN rises, the PNP sinks current from the ADJ rail. The output voltage at start up is the addition of
the 1.25-V reference plus the drop across the base to emitter. While this is happening, the capacitor begins to
charge and eventually opens the PNP. At this point, the device functions normally, regulating the output at 15 V.
A diode is placed between C1 and VOUT to provide a path for the capacitor to discharge. Such controlled turnon
is useful for limiting the in-rush current.
Figure 21. Slow Turnon 15-V Regulator
9.2.4 Adjustable Regulator With Improved Ripple Rejection
To improve ripple rejection, a capacitor is used to bypass the ADJ pin to GND (see Figure 22). This is used to
smooth output ripple by cleaning the feedback path and stopping unnecessary noise from being fed back into the
device, propagating the noise.
NOTE: †Solid tantalum
*Discharges C1 if output is shorted to ground
Figure 22. Adjustable Regulator With Improved Ripple Rejection
three LM195 devices in parallel
LM317A
R3
267
1%
R2
1.5 k
1%
R1
2 k
5%
C1
0.1 µF
LM329
VIN
15 V
VOUT
10 V
VIN VOUT
LM317A
ADJ
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Typical Applications (continued)
9.2.5 High-Stability 10-V Regulator
Using a high-stability shunt voltage reference in the feedback path, such as the LM329, provides damping
necessary for a stable, low noise output (see Figure 23).
Figure 23. High-Stability 10-V Regulator
9.2.6 High-Current Adjustable Regulator
Using the LM195 power transistor in parallel with the LM317A can increase the maximum possible output load
current (see Figure 24). Sense resistor R1 provides the 0.6 V across base to emitter to turn on the PNP. This on
switch allows current to flow, and the voltage drop across R3 drives three LM195 power transistors designed to
carry an excess of 1 A each.
NOTE
The selection of R1 determines a minimum load current for the PNP to turn on. The higher
the resistor value, the lower the load current must be before the transistors turn on.
NOTE: ‡Optional—improves ripple rejection
†Solid tantalum
*Minimum load current = 30 mA
Figure 24. High-Current Adjustable Regulator
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Typical Applications (continued)
9.2.7 Emitter-Follower Current Amplifier
The LM317A is used as a constant-current source in the emitter-follower circuit (see Figure 25). The LM195
power transistor is being used as a current-gain amplifier, boosting the INPUT current. The LM317A provides a
more stable current bias than a current bias from a system using only a resistor.
Figure 25. Emitter-Follower Current Amplifier
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Typical Applications (continued)
9.2.8 1-A Current Regulator
A simple, fixed-current regulator can be made by placing a resistor between the VOUT and ADJ pins of the
LM317A (see Figure 26). By regulating a constant 1.25 V between these two terminals, a constant current is
delivered to the load.
Figure 26. 1-A Current Regulator
9.2.9 Common-Emitter Amplifier
Sometimes it is necessary to use a power transistor for high current gain. In this case, the LM317A provides
constant current at the collector of the LM195 in this common emitter application (see Figure 27). The 1.25-V
reference between VOUT and ADJ is maintained across the 2.4-Ωresistor, providing about 500-mA constant bias
current into the collector of the LM195.
Figure 27. Common-Emitter Amplifier
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Typical Applications (continued)
9.2.10 Low-Cost 3-A Switching Regulator
The LM317A can be used in a switching buck regulator application in cost sensitive applications that require high
efficiency. The switch node above D1 oscillates between ground and VIN, as the voltage across sense resistor
R1 drives the power transistor on and off. Figure 28 exhibits self-oscillating behavior by negative feedback
through R6 and C3 to the ADJ pin of the LM317A.
NOTE: †Solid tantalum
*Core—Arnold A-254168-2 60 turns
Figure 28. Low-Cost 3-A Switching Regulator
mV
Short circuit current is approximately , or 210 mA
R
600
3
-
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Typical Applications (continued)
9.2.11 Current-Limited Voltage Regulator
A maximum limit on output current can be set using Figure 29. The load current travels through R3 and R4. As
the load current increases, the voltage drop across R3 increases until the NPN transistor is driven, during which
the ADJ pin is pulled down to ground and the output voltage is pulled down to the reference voltage of 1.25 V.
(Compared to LM117's higher current limit)
—At 50 mA output only ¾ volt of drop occurs in R3and R4
Figure 29. Current-Limited Voltage Regulator
9.2.12 Adjusting Multiple On-Card Regulators With Single Control
Figure 30 shows how multiple LM317A regulators can be controlled by setting one resistor. Because each device
maintains the reference voltage of about 1.25 V between its VOUT and ADJ pins, we can connect each ADJ rail to
a single resistor, setting the same output voltage across all devices. This allows for independent outputs, each
responding to its corresponding input only. Designers must also consider that by the nature of the circuit,
changes to R1 and R2 will affect all regulators.
NOTE: *All outputs within ±100 mV
†Minimum load—10 mA
Figure 30. Adjusting Multiple On-Card Regulators With Single Control
LM317A
LM317A
LM317A
22
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Typical Applications (continued)
9.2.13 AC Voltage Regulator
In Figure 31, the top regulator is 6 V above the bottom regulator. It is clear that when the input rises above 6 V
plus the dropout voltage, only the top LM317A regulates 6 V at the output. When the input falls below –6 V minus
the dropout voltage, only the bottom LM317A regulates –6 V at the output. For regions where the output is not
clipped, there is no regulation taking place, so the output follows the input.
Figure 31. AC Voltage Regulator
9.2.14 12-V Battery Charger
The LM317A can be used in a battery charger application shown in Figure 32, where the device maintains either
constant voltage or constant current mode depending on the current charge of the battery. To do this, the part
senses the voltage drop across the battery and delivers the maximum charging current necessary to charge the
battery. When the battery charge is low, there exists a voltage drop across the sense resistor RS, providing
constant current to the battery at that instant. As the battery approaches full charge, the potential drop across RS
approaches zero, reducing the current and maintaining the fixed voltage of the battery.
Use of RSallows low charging rates with fully charged battery.
Figure 32. 12-V Battery Charger
LM317A
LM317A
LM317A
23
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Typical Applications (continued)
9.2.15 Adjustable 4-A Regulator
Using three LM317A devices in parallel increases load-current capability (see Figure 33). Output voltage is set by
the variable resistor tied to the noninverting terminal of the operational amplifier, and reference current to the
transistor is developed across the 100-Ωresistor. When output voltage rises, the operational amplifier corrects by
drawing current from the base, closing the transistor. This effectively pulls ADJ down and lowers the output
voltage through negative feedback.
Figure 33. Adjustable 4-A Regulator
LM317A
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Typical Applications (continued)
9.2.16 Current-Limited 6-V Charger
The current in a battery charger application is limited by switching between constant current and constant voltage
states (see Figure 34). When the battery pulls low current, the drop across the 1 Ωresistor is not substantial and
the NPN remains off. A constant voltage is seen across the battery, as regulated by the resistor divider. When
current through the battery rises past peak current, the 1 Ωprovides enough voltage to turn the transistor on,
pulling ADJ close to ground. This results in limiting the maximum current to the battery.
NOTE: *Sets peak current (0.6A for 1Ω)
**The 1000-μF is recommended to filter out input transients
Figure 34. Current-Limited 6-V Charger
9.2.17 Digitally-Selected Outputs
Figure 35 demonstrates a digitally-selectable output voltage. In its default state, all transistors are off and the
output voltage is set based on R1 and R2. By driving certain transistors, the associated resistor is connected in
parallel to R2, modifying the output voltage of the regulator.
NOTE: *Sets maximum VOUT
Figure 35. Digitally-Selected Outputs
25
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10 Power Supply Recommendations
The input supply to the LM317A should be kept at a voltage level lower than the maximum input-to-output
differential voltage of 40 V. When possible, the minimum dropout voltage should also be met with extra
headroom to keep the LM317A in regulation. TI recommends the use of an input capacitor, especially when the
input pin is located more than 6 inches away from the power supply source. For more information regarding
capacitor selection, refer to External Capacitors.
11 Layout
11.1 Layout Guidelines
Some layout guidelines should be followed to ensure proper regulation of the output voltage with minimum noise.
Traces carrying the load current should be wide to reduce the amount of parasitic trace inductance and the
feedback loop from VOUT to ADJ should be kept as short as possible. To improve PSRR, a bypass capacitor can
be placed at the ADJ pin and should be located as close as possible to the IC. In cases when VIN shorts to
ground, an external diode should be placed from VOUT to VIN to divert the surge current from the output capacitor
and protect the IC. Similarly, in cases when a large bypass capacitor is placed at the ADJ pin and VOUT shorts to
ground, an external diode should be placed from ADJ to VOUT to provide a path for the bypass capacitor to
discharge. These diodes should be placed close to the corresponding IC pins to increase their effectiveness.
11.1.1 Thermal Considerations
11.1.1.1 Heatsink Requirements
The LM317A regulators have internal thermal shutdown to protect the device from over-heating. Under all
operating conditions, the junction temperature of the LM317A should not exceed the rated maximum junction
temperature (TJ) of 125°C. A heatsink may be required depending on the maximum device power dissipation and
the maximum ambient temperature of the application. To determine if a heatsink is needed, the power dissipated
by the regulator, PD, must be calculated by Equation 2:
PD= ((VIN −VOUT) × IL) + (VIN × IG) (2)
Figure 36 shows the voltage and currents which are present in the circuit.
The next parameter which must be calculated is the maximum allowable temperature rise, TR(MAX) in Equation 3:
TR(MAX) = TJ(MAX) −TA(MAX)
where
• TJ(MAX) is the maximum allowable junction temperature (125°C for the LM317A),
• and TA(MAX) is the maximum ambient temperature that will be encountered in the application. (3)
Using the calculated values for TR(MAX) and PD, the maximum allowable value for the junction-to-ambient thermal
resistance (θJA) can be calculated by Equation 4:
θJA = (TR(MAX) / PD) (4)
Figure 36. Power Dissipation Diagram
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Layout Guidelines (continued)
If the calculated maximum allowable thermal resistance is higher than the actual package rating, then no
additional work is needed. If the calculated maximum allowable thermal resistance is lower than the actual
package rating, either the power dissipation (PD) needs to be reduced, the maximum ambient temperature
TA(MAX) needs to be reduced, the thermal resistance (θJA) must be lowered by adding a heatsink, or some
combination of these measures should be implemented.
If a heatsink is needed, the value can be calculated from Equation 5:
θHA ≤(θJA – (θCH +θJC))
where
•θCH is the thermal resistance of the contact area between the device case and the heatsink surface
•θJC is thermal resistance from the junction of the die to surface of the package case (5)
When a value for θHA is found using the equation shown, a heatsink must be selected that has a value that is
less than or equal to this number.
The θHA rating is specified numerically by the heatsink manufacturer in the catalog, or shown in a curve that plots
temperature rise vs power dissipation for the heatsink.
11.1.1.2 Heatsinking Surface Mount Packages
The SOT-223 (DCY) and TO-252 (NDP) packages use a copper plane on the PCB and the PCB itself as a
heatsink. To optimize the heat-sinking ability of the plane and PCB, solder the tab of the package to the plane.
11.1.1.2.1 Heatsinking the SOT-223 (DCY) Package
Figure 37 and Figure 38 show the information for the SOT-223 package. Figure 38 assumes a θJA of 74°C/W for
1-oz. copper and 59.6°C/W for 2-oz. copper and a maximum junction temperature of 125°C. See the AN-1028
Maximum Power Enhancement Techniques for Power Packages application note for thermal enhancement
techniques to be used with SOT-223 and TO-252 packages.
Figure 37. θJA vs Copper (2-oz.) Area for the SOT-223
Package
Figure 38. Maximum Power Dissipation vs TAMB for the
SOT-223 Package
11.1.1.2.2 Heatsinking the TO-252 (NDP) Package
If the maximum allowable value for θJA is found to be ≥54°C/W (typical rated value) for the TO-252 package, no
heatsink is needed because 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 1 shows the value of the θJA of NDP the package for different heatsink area. The copper
patterns that we used to measure these θJAs are shown in Figure 43.Figure 39 reflects the same test results as
what are in Table 1.
27
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Layout Guidelines (continued)
(1) Tab of device attached to topside of copper.
Figure 40 shows the maximum allowable power dissipation versus ambient temperature for the TO-252 device.
Figure 41 shows the maximum allowable power dissipation versus copper area (in2) for the TO-252 device. See
the AN-1028 Maximum Power Enhancement Techniques for Power Packages application note for thermal
enhancement techniques to be used with SOT-223 and TO-252 packages.
Table 1. θJA Different Heatsink Area
Layout Copper Area Thermal Resistance
Top Side (in2)(1) Bottom Side (in2) (θJA°C/W) TO-252
1 0.0123 0 103
2 0.066 0 87
3 0.3 0 60
4 0.53 0 54
5 0.76 0 52
6 1 0 47
7 0.066 0.2 84
8 0.066 0.4 70
9 0.066 0.6 63
10 0.066 0.8 57
11 0.066 1 57
12 0.066 0.066 89
13 0.175 0.175 72
14 0.284 0.284 61
15 0.392 0.392 55
16 0.5 0.5 53
Figure 39. θJA vs 2-oz. Copper Area for TO-252 Figure 40. Maximum Allowable Power Dissipation vs
Ambient Temperature for TO-252
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Figure 41. Maximum Allowable Power Dissipation vs 2-oz. Copper Area for TO-252
Figure 42. Top View of the Thermal Test Pattern in Actual Scale
32
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12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Related Documentation
For related documentation see the following:
• Texas Instruments, LM150/LM350A/LM350 3-Amp Adjustable Regulators data sheet
• Texas Instruments, LM138 and LM338 5-Amp Adjustable Regulators data sheet
• Texas Instruments, LM137, LM337-N 3-Terminal Adjustable Negative Regulators data sheet
• Texas Instruments, AN-1028 Maximum Power Enhancement Techniques for Power Packages application
note
12.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.3 Support Resources
TI E2E™ support forums are an engineer's go-to source for fast, verified answers and design help — straight
from the experts. Search existing answers or ask your own question to get the quick design help you need.
Linked content is provided "AS IS" by the respective contributors. They do not constitute TI specifications and do
not necessarily reflect TI's views; see TI's Terms of Use.
12.4 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.5 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
12.6 Glossary
SLYZ022 —TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
PACKAGE OPTION ADDENDUM
www.ti.com 11-Jan-2021
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead finish/
Ball material
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LM317AEMP NRND SOT-223 DCY 4 1000 Non-RoHS
& Green Call TI Call TI -40 to 125 N07A
LM317AEMP/NOPB ACTIVE SOT-223 DCY 4 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 N07A
LM317AEMPX NRND SOT-223 DCY 4 2000 Non-RoHS
& Green Call TI Call TI N07A
LM317AEMPX/NOPB ACTIVE SOT-223 DCY 4 2000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 N07A
LM317AH ACTIVE TO NDT 3 500 RoHS & Green AU Level-1-NA-UNLIM -40 to 125 ( LM317AHP+, LM317
AHP+)
LM317AH/NOPB ACTIVE TO NDT 3 500 RoHS & Green AU Level-1-NA-UNLIM -40 to 125 ( LM317AHP+, LM317
AHP+)
LM317AMDT NRND TO-252 NDP 3 75 Non-RoHS
& Green Call TI Call TI -40 to 125 LM317
AMDT
LM317AMDT/NOPB ACTIVE TO-252 NDP 3 75 RoHS & Green SN Level-2-260C-1 YEAR -40 to 125 LM317
AMDT
LM317AMDTX NRND TO-252 NDP 3 2500 Non-RoHS
& Green Call TI Call TI -40 to 125 LM317
AMDT
LM317AMDTX/NOPB ACTIVE TO-252 NDP 3 2500 RoHS & Green SN Level-2-260C-1 YEAR -40 to 125 LM317
AMDT
LM317AT NRND TO-220 NDE 3 45 Non-RoHS
& Green Call TI Call TI -40 to 125 LM317AT P+
LM317AT/NOPB ACTIVE TO-220 NDE 3 45 RoHS-Exempt
& Green SN Level-1-NA-UNLIM -40 to 125 LM317AT P+
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
PACKAGE OPTION ADDENDUM
www.ti.com 11-Jan-2021
Addendum-Page 2
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two
lines if the finish value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LM317AEMP SOT-223 DCY 4 1000 330.0 16.4 7.0 7.5 2.2 12.0 16.0 Q3
LM317AEMP/NOPB SOT-223 DCY 4 1000 330.0 16.4 7.0 7.5 2.2 12.0 16.0 Q3
LM317AEMPX SOT-223 DCY 4 2000 330.0 16.4 7.0 7.5 2.2 12.0 16.0 Q3
LM317AEMPX/NOPB SOT-223 DCY 4 2000 330.0 16.4 7.0 7.5 2.2 12.0 16.0 Q3
LM317AMDTX TO-252 NDP 3 2500 330.0 16.4 6.9 10.5 2.7 8.0 16.0 Q2
LM317AMDTX/NOPB TO-252 NDP 3 2500 330.0 16.4 6.9 10.5 2.7 8.0 16.0 Q2
PACKAGE MATERIALS INFORMATION
www.ti.com 9-Jun-2020
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LM317AEMP SOT-223 DCY 4 1000 367.0 367.0 35.0
LM317AEMP/NOPB SOT-223 DCY 4 1000 367.0 367.0 35.0
LM317AEMPX SOT-223 DCY 4 2000 367.0 367.0 35.0
LM317AEMPX/NOPB SOT-223 DCY 4 2000 367.0 367.0 35.0
LM317AMDTX TO-252 NDP 3 2500 367.0 367.0 35.0
LM317AMDTX/NOPB TO-252 NDP 3 2500 367.0 367.0 38.0
PACKAGE MATERIALS INFORMATION
www.ti.com 9-Jun-2020
Pack Materials-Page 2
MECHANICAL DATA
NDE0003B
www.ti.com
MECHANICAL DATA
MPDS094A – APRIL 2001 – REVISED JUNE 2002
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
DCY (R-PDSO-G4) PLASTIC SMALL-OUTLINE
4202506/B 06/2002
6,30 (0.248)
6,70 (0.264)
2,90 (0.114)
3,10 (0.122)
6,70 (0.264)
7,30 (0.287) 3,70 (0.146)
3,30 (0.130)
0,02 (0.0008)
0,10 (0.0040)
1,50 (0.059)
1,70 (0.067)
0,23 (0.009)
0,35 (0.014)
1 2 3
4
0,66 (0.026)
0,84 (0.033)
1,80 (0.071) MAX
Seating Plane
0°–10°
Gauge Plane
0,75 (0.030) MIN
0,25 (0.010)
0,08 (0.003)
0,10 (0.004) M
2,30 (0.091)
4,60 (0.181) M
0,10 (0.004)
NOTES: A. All linear dimensions are in millimeters (inches).
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or protrusion.
D. Falls within JEDEC TO-261 Variation AA.
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PACKAGE OUTLINE
C
10.42
9.40
6.73
6.35
6.22
5.97 1.27
0.88
5.46
4.96
2.285
4.57
1.02
0.64
3X 0.88
0.64
2.55 MAX
0.88
0.46
8
8
1.14
0.89
0.60
0.46
0.17
0.51 MIN
4.32 MIN
(2.345)
(2.5)
TO-252 - 2.55 mm max heightNDP0003B
TRANSISTOR OUTLINE
4219870/A 03/2018
NOTES:
1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing
per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. Reference JEDEC registration TO-252.
0.25 C A B
TOP & BOTTOM
PKG
1
2
3
OPTIONAL
SEATING PLANE
4
3
2
1
SCALE 1.500
A
B
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EXAMPLE BOARD LAYOUT
0.07 MAX
ALL AROUND 0.07 MIN
ALL AROUND
(4.57)
2X (1.3) 2X (2.15) (5.7)
(5.5)
(2.285)(4.38)
(R0.05) TYP
TO-252 - 2.55 mm max heightNDP0003B
TRANSISTOR OUTLINE
4219870/A 03/2018
NOTES: (continued)
4. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature numbers
SLMA002(www.ti.com/lit/slm002) and SLMA004 (www.ti.com/lit/slma004).
5. Vias are optional depending on application, refer to device data sheet. It is recommended that vias under paste be filled, plugged or tented.
LAND PATTERN EXAMPLE
EXPOSED METAL SHOWN
SCALE: 8X
SYMM
PKG
1
3
4
SEE SOLDER MASK
DETAIL
EXPOSED
METAL
METAL EDGE
SOLDER MASK
OPENING
NON SOLDER MASK
DEFINED
(PREFERRED) SOLDER MASK DETAIL
EXPOSED
METAL
METAL UNDER
SOLDER MASK
SOLDER MASK
OPENING
SOLDER MASK DEFINED
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EXAMPLE STENCIL DESIGN
2X (2.15)
2X (1.3)
(4.57)
(4.38)
(1.32) TYP
(1.35) TYP
(0.26) (R0.05) TYP
16X (1.12)
16X (1.15)
TO-252 - 2.55 mm max heightNDP0003B
TRANSISTOR OUTLINE
4219870/A 03/2018
NOTES: (continued)
6. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
7. Board assembly site may have different recommendations for stencil design.
PKG
SOLDER PASTE EXAMPLE
BASED ON 0.125 MM THICK STENCIL
SCALE: 8X
MECHANICAL DATA
NDT0003A
www.ti.com
H03A (Rev D)
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