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An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.

LM117

LM317-N

SNVS774Q –MAY 2004–REVISED JUNE 2020

LM117, LM317-N Wide Temperature Three-Pin Adjustable Regulator

1 Features

1• For a newer drop-in alternative, see the LM317

• Typ. 0.1% load regulation

• Typ. 0.01%/V line regulation

• 1.5-A output current

• Adjustable output down to 1.25 V

• Current limit constant with temperature

• 80-dB ripple rejection

• Short-circuit protected output

•−55°C to 150°C operating temperature range

(LM117)

2 Applications

•Multifunction printers

•AC drive power stage modules

•Electricity meters

•Servo drive control modules

•Merchant network and server PSU

Typical Application

*Needed if device is more than 6 inches from filter

capacitors.

†Optional—improves transient response

††

3 Description

The LM117 and LM317-N series of adjustable 3-pin

positive voltage regulators are capable of supplying in

excess of 1.5 A over a 1.25-V to 37-V output range

and a wide temperature range. They are

exceptionally easy to use and require only two

external resistors to set the output voltage. Further,

both line and load regulation are better than standard

fixed regulators.

The LM117 and LM317-N offer full overload

protection such as current limit, 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. 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 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.

That is, avoid short-circuiting the output.

By connecting a fixed resistor between the

adjustment pin and output, the LM117 and LM317-N

can be also used as a precision current regulator.

Supplies with electronic shutdown can be achieved

by clamping the adjustment terminal to ground, which

programs the output to 1.25 V where most loads draw

little current.

For applications requiring greater output current, see

the LM150 series (3 A) and LM138 series (5 A) data

sheets. For the negative complement, see the LM137

series data sheet.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)

LM117 TO-3 (2) 38.94 mm x 25.40 mm

TO (3) 8.255 mm × 8.255 mm

LM317-N

TO-3 (2) 38.94 mm x 25.40 mm

TO-220 (3) 14.986 mm × 10.16 mm

TO-263 (3) 10.18 mm × 8.41 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.

LM117

LM317-N

SNVS774Q –MAY 2004–REVISED JUNE 2020

www.ti.com

Product Folder Links: LM117 LM317-N

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......................................................... 6

7.1 Absolute Maximum Ratings ...................................... 6

7.2 ESD Ratings.............................................................. 6

7.3 Recommended Operating Conditions....................... 6

7.4 Thermal Information, LM117..................................... 6

7.5 Thermal Information, LM317-N................................. 7

7.6 LM117 Electrical Characteristics............................... 7

7.7 LM317-N Electrical Characteristics........................... 8

7.8 Typical Characteristics.............................................. 9

8 Detailed Description............................................ 12

8.1 Overview................................................................. 12

8.2 Functional Block Diagram....................................... 13

8.3 Feature Description................................................. 14

8.4 Device Functional Modes........................................ 14

9 Application and Implementation ........................ 16

9.1 Application Information............................................ 16

9.2 Typical Applications ................................................ 16

10 Power Supply Recommendations ..................... 28

11 Layout................................................................... 28

11.1 Layout Guidelines ................................................. 28

11.2 Layout Examples................................................... 34

12 Device and Documentation Support................. 36

12.1 Documentation Support ........................................ 36

12.2 Related Links ........................................................ 36

12.3 Receiving Notification of Documentation Updates 36

12.4 Support Resources ............................................... 36

12.5 Trademarks........................................................... 36

12.6 Electrostatic Discharge Caution............................ 36

12.7 Glossary................................................................ 36

13 Mechanical, Packaging, and Orderable

Information........................................................... 37

4 Revision History

NOTE: Page numbers for previous revisions may differ from page numbers in the current version.

Changes from Revision P (October 2015) to Revision Q Page

• Added alternative device Features bullet ............................................................................................................................... 1

• Changed Applications section ............................................................................................................................................... 1

• Changed Device Comparison Table ...................................................................................................................................... 3

• Changed Related Documentation section............................................................................................................................ 36

Changes from Revision O (January 2014) to Revision P Page

• Added, updated, or renamed the following sections: Description;Pin Configuration and Functions;Specifications;

ESD Ratings table; Application and Implementation;Power Supply Recommendations;Layout;Mechanical,

Packaging, and Ordering Information .................................................................................................................................... 1

• Removed information regarding LM317A, formerly part of this data sheet. LM317A can now be found in the TI

catalog under literature number SNVSAC2 ........................................................................................................................... 1

Changes from Revision N (August 2013) to Revision O Page

• Deleted MDT Package (over Full Operating Temperature Range) ....................................................................................... 8

• Changed Current Limit MIN from 0.112 to 0.15 and TYP from 0.3 to 0.4 for (VIN – VOUT) = 40 V in the LM317A

and LM317-N Electrical Characteristics Section .................................................................................................................... 8

• Deleted MDT Package ........................................................................................................................................................... 8

LM117

LM317-N

www.ti.com

SNVS774Q –MAY 2004–REVISED JUNE 2020

Product Folder Links: LM117 LM317-N

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

LM117

LM317-N

SNVS774Q –MAY 2004–REVISED JUNE 2020

www.ti.com

Product Folder Links: LM117 LM317-N

6 Pin Configuration and Functions

NDS Metal Can Package

2-Pin TO-3

Bottom View

Case is Output

NDT Metal Can Package

3-Pin TO

Bottom View

Case is Output

Pin Functions, Metal Can Packages

PIN I/O DESCRIPTION

NAME TO-3 TO

ADJ 1 2 — Adjust pin

VOUT CASE 3, CASE O Output voltage pin for the regulator

VIN 2 1 I Input voltage pin for the regulator

LM117

LM317-N

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SNVS774Q –MAY 2004–REVISED JUNE 2020

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KTT Surface-Mount Package

3-Pin DDPAK/TO-263

Top View

NDE Plastic Package

3-Pin TO-220

Front View

DCY Surface-Mount Package

4-Pin SOT-223

Top View

NDP Surface-Mount Package

3-Pin TO-252

Front View

Pin Functions

PIN I/O DESCRIPTION

NAME TO-263 TO-220 SOT-223 TO-252

ADJ 1 1 1 1 — Adjust pin

VOUT 2, TAB 2, TAB 2, 4 2, TAB O Output voltage pin for the regulator

VIN 3 3 3 3 I Input voltage pin for the regulator

LM117

LM317-N

SNVS774Q –MAY 2004–REVISED JUNE 2020

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Product Folder Links: LM117 LM317-N

(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 (LM117) −55 150 °C

Operating temperature (LM317-N) 0 125 °C

(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC package thermal metrics application

report.

(2) No heatsink.

7.4 Thermal Information, LM117

THERMAL METRIC(1)

LM117

UNIT

NDS

(TO-3) NDT

(TO)

2 PINS 3 PINS

RθJA Junction-to-ambient thermal resistance(2) 39 186 °C/W

RθJC(top) Junction-to-case (top) thermal resistance 2 21 °C/W

LM117

LM317-N

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SNVS774Q –MAY 2004–REVISED JUNE 2020

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(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.

7.5 Thermal Information, LM317-N

THERMAL METRIC(1)(2)

LM317-N

UNIT

KTT

(TO-263) NDE

(TO-220) DCY

(SOT-223) NDT

(TO) NDP

(TO-252)

3 PINS 3 PINS 4 PINS 3 PINS 3 PINS

RθJA Junction-to-ambient thermal resistance 41.0 23.3 59.6 186(3) 54 °C/W

RθJC(top) Junction-to-case (top) thermal resistance 43.6 16.2 39.3 21 51.3 °C/W

RθJB Junction-to-board thermal resistance 23.6 4.9 8.4 — 28.6 °C/W

ψJT Junction-to-top characterization parameter 10.4 2.7 1.8 — 3.9 °C/W

ψJB Junction-to-board characterization parameter 22.6 4.9 8.3 — 28.1 °C/W

RθJC(bot) Junction-to-case (bottom) thermal resistance 0.9 1.1 — — 0.9 °C/W

(1) IMAX = 1.5 A for the NDS (TO-3), NDE (TO-220), and KTT (TO-263) packages. 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 (RθJA). The maximum allowable power dissipation at any

temperature is : PD(MAX) = ((TJ(MAX) – TA) / RθJA). All Min. and Max. limits are ensured to TI's Average Outgoing Quality Level (AOQL).

(2) Specifications and availability for military and space grades of LM117/883 can be found in the LM117QML data sheet. Specifications

and availability for military and space grades of LM117 can be found in the LM117JAN data sheet.

(3) 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.

7.6 LM117 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)(2)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Reference voltage 3 V ≤(VIN −VOUT)≤40 V,

10 mA ≤IOUT ≤IMAX(1) (over full operating temperature range) 1.2 1.25 1.3 V

Line regulation 3 V ≤(VIN −VOUT)≤40 V(3) TJ= 25°C 0.01 0.02 %/V

over full operating

temperature range 0.02 0.05

Load regulation 10 mA ≤IOUT ≤IMAX(1)(3) TJ= 25°C 0.1% 0.3%

over full operating

temperature range 0.3% 1%

Thermal regulation 20-ms pulse 0.03 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 5 mA

Current limit (VIN −VOUT)≤15 V

TO-3 Package (over full

operating temperature range) 1.5 2.2 3.4 A

TO-39 Package (over full

operating temperature range) 0.5 0.8 1.8

(VIN −VOUT) = 40 V TO-3 package 0.3 0.4 A

TO-39 package 0.15 0.2

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%

LM117

LM317-N

SNVS774Q –MAY 2004–REVISED JUNE 2020

www.ti.com

Product Folder Links: LM117 LM317-N

(1) IMAX = 1.5 A for the NDS (TO-3), NDE (TO-220), and KTT (TO-263) packages. 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 (RθJA). The maximum allowable power dissipation at any

temperature is : PD(MAX) = ((TJ(MAX) – TA) / RθJA). All Min. and Max. 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.

7.7 LM317-N Electrical Characteristics(1)

Some specifications apply over full Operating Temperature Range as noted. Unless otherwise specified, TJ= 25°C, VIN −

VOUT = 5 V, and IOUT = 10 mA.

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Reference voltage

TJ= 25°C 1.25 V

3 V ≤(VIN −VOUT)≤40 V,

10 mA ≤IOUT ≤IMAX(1) (over Full Operating Temperature

Range) 1.2 1.25 1.3 V

Line regulation 3V ≤(VIN −VOUT)≤40 V(2) TJ= 25°C 0.01 0.04 %/V

(over full operating

temperature range) 0.02 0.07

Load regulation 10 mA ≤IOUT ≤IMAX(1)(2) TJ= 25°C 0.1% 0.5%

(over full operating

temperature range) 0.3% 1.5%

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)

3V ≤(VIN −VOUT)≤40V (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

TO-3, TO-263 Packages

(over full operating

temperature range) 1.5 2.2 3.4

SOT-223, TO-220

Packages (over full

operating temperature

range) 1.5 2.2 3.4

TO, TO-252 Package (over

full operating temperature

range) 0.5 0.8 1.8

(VIN −VOUT) = 40 V TO-3, TO-263 packages 0.15 0.4 ASOT-223, TO-220 packages 0.15 0.4

TO, TO-252 package 0.075 0.2

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 = 10V, 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%

LM117

LM317-N

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SNVS774Q –MAY 2004–REVISED JUNE 2020

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7.8 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 = 5 V

LM117

LM317-N

SNVS774Q –MAY 2004–REVISED JUNE 2020

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Product Folder Links: LM117 LM317-N

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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LM317-N

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Typical Characteristics (continued)

output Capacitor = 0 μF (unless otherwise noted)

Figure 13. Line Transient Response Figure 14. Load Transient Response

LM317-N

( )

OUT ADJ

V = 1.25 V I R

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LM117

LM317-N

SNVS774Q –MAY 2004–REVISED JUNE 2020

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8 Detailed Description

8.1 Overview

In operation, the LM317-N 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 LM317-N 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.

LM117

LM317-N

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8.2 Functional Block Diagram

LM317-N

LM117

LM317-N

SNVS774Q –MAY 2004–REVISED JUNE 2020

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8.3 Feature Description

8.3.1 Load Regulation

The LM317-N is capable of providing extremely good load regulation but a few precautions are needed to obtain

maximum performance. The current set resistor, R1, must 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

must 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-3 package, it is easy to minimize the resistance from the case to the set resistor, by using two

separate leads to the case. However, with the TO package, care must 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 LM317-N 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 capacitors 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 LM317-N 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

V = 1.25 V I R

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LM317-N

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LM317-N

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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 LM317-N, 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 LM317-N 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 LM317-N 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

LM317-N

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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 must

validate and test their design implementation to confirm system functionality.

9.1 Application Information

The LM117 and LM317-N are versatile, high performance, linear regulators with high accuracy and a wide

temperature range. 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 LM117 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.

LM317-N

LM117

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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 L117 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 LM117 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 ≊1.2 V

Figure 20. 5-V Logic Regulator With Electronic Shutdown

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SNVS774Q –MAY 2004–REVISED JUNE 2020

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Product Folder Links: LM117 LM317-N

Typical Applications (continued)

9.2.3 Slow Turnon 15-V Regulator

An application of LM117 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

267 

1.5 k

2 k

0.1 µF

LM329

VIN

15 V

VOUT

10 V

VIN VOUT

LM117

ADJ

LM317-N

LM117

LM317-N

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SNVS774Q –MAY 2004–REVISED JUNE 2020

Product Folder Links: LM117 LM317-N

Typical Applications (continued)

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

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