LM317L
March 23, 2010
3-Terminal Adjustable Regulator
General Description
The LM317L is an adjustable 3-terminal positive voltage reg-
ulator capable of supplying 100mA over a 1.2V to 37V output
range. It is exceptionally easy to use and requires only two
external resistors to set the output voltage. Further, both line
and load regulation are better than standard fixed regulators.
Also, the LM317L is available packaged in a standard TO-92
transistor package which is easy to use.
In addition to higher performance than fixed regulators, the
LM317L offers full overload protection. Included on the chip
are current limit, thermal overload protection and safe area
protection. All overload protection circuitry remains fully func-
tional even if the adjustment terminal is disconnected.
Normally, no capacitors are needed unless the device is sit-
uated more than 6 inches from the input filter capacitors in
which case an input bypass is needed. An optional output ca-
pacitor can be added to improve transient response. The
adjustment terminal can be bypassed to achieve very high
ripple rejection ratios which are difficult to achieve with stan-
dard 3-terminal regulators.
Besides replacing fixed regulators, the LM317L is useful in a
wide variety of other applications. Since the regulator is “float-
ing” and sees 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.
Also, it makes an especially simple adjustable switching reg-
ulator, a programmable output regulator, or by connecting a
fixed resistor between the adjustment and output, the LM317L
can be used as a precision current regulator. Supplies with
electronic shutdown can be achieved by clamping the adjust-
ment terminal to ground which programs the output to 1.2V
where most loads draw little current.
The LM317L is available in a standard TO-92 transistor pack-
age, the SO-8 package, and 6-Bump micro SMD package.
The LM317L is rated for operation over a −40°C to 125°C
range.
Features
Adjustable output down to 1.2V
Guaranteed 100mA output current
Line regulation typically 0.01%V
Load regulation typically 0.1%
Current limit constant with temperature
Eliminates the need to stock many voltages
Standard 3-lead transistor package
80dB ripple rejection
Available in TO-92, SO-8, or 6-Bump micro SMD package
Output is short circuit protected
See AN-1112 for micro SMD considerations
Connection Diagrams
TO-92 Plastic package
906404
8-Pin SOIC
906405
Top View
© 2010 National Semiconductor Corporation 9064 www.national.com
LM317L 3-Terminal Adjustable Regulator
6-Bump micro SMD
906449
*NC = Not Internally connected.
Top View
(Bump Side Down)
micro SMD Laser Mark
906450
Ordering Information
Package Part Number Package Marking Media Transport NSC Drawing
TO-92 LM317LZ LM317LZ 1.8k Units per Box Z03A
8-Pin SOIC LM317LM LM317LM Rails M08A
6-Bump micro SMD
* LM317LIBP 250 Units Tape and Reel BPA06HPB
* LM317LIBPX 3k Units Tape and Reel
* LM317LITP 250 Units Tape and Reel TPA06HPA
* LM317LITPX 3k Units Tape and Reel
Note: The micro SMD package marking is a single digit manufacturing Date
Code only.
www.national.com 2
LM317L
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Power Dissipation Internally Limited
Input-Output Voltage Differential 40V
Operating Junction Temperature
Range −40°C to +125°C
Storage Temperature −55°C to +150°C
Lead Temperature
(Soldering, 4 seconds) 260°C
Output is Short Circuit Protected
ESD Susceptibility
Human Body Model (Note 5) 2kV
Electrical Characteristics (Note 2)
Parameter Conditions Min Typ Max Units
Line Regulation TJ = 25°C, 3V (VIN − VOUT) 40V, IL 20mA (Note 3) 0.01 0.04 %/V
Load Regulation TJ = 25°C, 5mA IOUT IMAX, (Note 3) 0.1 0.5 %
Thermal Regulation TJ = 25°C, 10ms Pulse 0.04 0.2 %/W
Adjustment Pin Current 50 100 μA
Adjustment Pin Current 5mA IL 100mA 0.2 5 μA
Change 3V (VIN − VOUT) 40V, P 625mW
Reference Voltage 3V (VIN − VOUT) 40V, (Note 4)1.20 1.25 1.30 V
5mA IOUT 100mA, P 625mW
Line Regulation 3V (VIN − VOUT) 40V, IL 20mA (Note 3) 0.02 0.07 %/V
Load Regulation 5mA IOUT 100mA, (Note 3) 0.3 1.5 %
Temperature Stability TMIN TJ TMax 0.65 %
Minimum Load Current (VIN − VOUT) 40V 3.5 5 mA
3V (VIN − VOUT) 15V 1.5 2.5
Current Limit 3V (VIN − VOUT) 13V 100 200 300 mA
(VIN − VOUT) = 40V 25 50 150 mA
Rms Output Noise, % of VOUT TJ = 25°C, 10Hz f 10kHz 0.003 %
Ripple Rejection Ratio VOUT = 10V, f = 120Hz, CADJ = 0 65 dB
CADJ = 10μF66 80 dB
Long-Term Stability TJ = 125°C, 1000 Hours 0.3 1 %
Thermal Resistance Z Package 0.4″ Leads 180 °C/W
Junction to Ambient Z Package 0.125 Leads 160 °C/W
SO-8 Package 165 °C/W
6-Bump micro SMD 290 °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 functional, but do not guarantee specific performance limits.
Note 2: Unless otherwise noted, these specifications apply: −25°C Tj 125°C for the LM317L; VIN − VOUT = 5V and IOUT = 40mA. Although power dissipation
is internally limited, these specifications are applicable for power dissipations up to 625mW. IMAX is 100mA.
Note 3: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects are
covered under the specification for thermal regulation.
Note 4: Thermal resistance of the TO-92 package is 180°C/W junction to ambient with 0.4″ leads from a PC board and 160°C/W junction to ambient with 0.125″
lead length to PC board.
Note 5: The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin.
3 www.national.com
LM317L
Typical Performance Characteristics (Output capacitor = 0μF unless otherwise noted.)
Load Regulation
906434
Current Limit
906435
Adjustment Current
906436
Dropout Voltage
906437
Reference Voltage Temperature Stability
906438
Minimum Operating Current
906439
www.national.com 4
LM317L
Ripple Rejection
906440
Ripple Rejection
906441
Output Impedance
906442
Line Transient Response
906443
Load Transient Response
906444
Thermal Regulation
906445
5 www.national.com
LM317L
Application Hints
In operation, the LM317L develops a nominal 1.25V reference
voltage, VREF, between the output and adjustment terminal.
The reference voltage is impressed across program resistor
R1 and, since the voltage is constant, a constant current I1
then flows through the output set resistor R2, giving an output
voltage of
Since the 100μA current from the adjustment terminal repre-
sents an error term, the LM317L 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 out-
put establishing a minimum load current requirement. If there
is insufficient load on the output, the output will rise.
906407
FIGURE 1.
EXTERNAL CAPACITORS
An input bypass capacitor is recommended in case the reg-
ulator is more than 6 inches away from the usual large filter
capacitor. A 0.1μF disc or 1μF solid tantalum on the input is
suitable input bypassing for almost all applications. The de-
vice is more sensitive to the absence of input bypassing when
adjustment or output capacitors are used, but the above val-
ues will eliminate the possibility of problems.
The adjustment terminal can be bypassed to ground on the
LM317L to improve ripple rejection and noise. This bypass
capacitor prevents ripple and noise from being amplified as
the output voltage is increased. With a 10μF bypass capacitor
80dB ripple rejection is obtainable at any output level. In-
creases over 10μF do not appreciably improve the ripple
rejection at frequencies above 120Hz. If the bypass capacitor
is used, it is sometimes necessary to include protection
diodes to prevent the capacitor from discharging through in-
ternal 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 25μF in aluminum electrolytic to equal 1μF solid tanta-
lum at high frequencies. Ceramic capacitors are also good at
high frequencies; but some types have a large decrease in
capacitance at frequencies around 0.5MHz. For this reason,
a 0.01μF disc may seem to work better than a 0.1μF disc as
a bypass.
Although the LM317L is stable with no output capacitors, like
any feedback circuit, certain values of external capacitance
can cause excessive ringing. This occurs with values be-
tween 500pF and 5000pF. A 1μF solid tantalum (or 25μF
aluminum electrolytic) on the output swamps this effect and
insures stability.
LOAD REGULATION
The LM317L is capable of providing extremely good load reg-
ulation but a few precautions are needed to obtain maximum
performance. The current set resistor connected between the
adjustment terminal and the output terminal (usually 240Ω)
should be tied directly to the output of the regulator rather than
near the load. This eliminates line drops from appearing ef-
fectively in series with the reference and degrading regula-
tion. For example, a 15V regulator with 0.05Ω resistance
between the regulator and load will have a load regulation due
to line resistance of 0.05Ω × IL. If the set resistor is connected
near the load the effective line resistance will be 0.05Ω (1 +
R2/R1) or in this case, 11.5 times worse.
Figure 2 shows the effect of resistance between the regulator
and 240Ω set resistor.
With the TO-92 package, it is easy to minimize the resistance
from the case to the set resistor, by using two separate leads
to the output pin. The ground of R2 can be returned near the
ground of the load to provide remote ground sensing and im-
prove load regulation.
906408
FIGURE 2. Regulator with Line Resistance
in Output Lead
THERMAL REGULATION
When power is dissipated in an IC, a temperature gradient
occurs across the IC chip affecting the individual IC circuit
components. With an IC regulator, this gradient can be espe-
cially severe since power dissipation is large. Thermal regu-
lation is the effect of these temperature gradients on output
voltage (in percentage output change) per watt of power
change in a specified time. Thermal regulation error is inde-
pendent of electrical regulation or temperature coefficient,
and occurs within 5ms to 50ms after a change in power dis-
sipation. Thermal regulation depends on IC layout as well as
electrical design. The thermal regulation of a voltage regulator
is defined as the percentage change of VOUT, per watt, within
the first 10ms after a step of power is applied. The LM317L
specification is 0.2%/W, maximum.
In the Thermal Regulation curve at the bottom of the Typical
Performance Characteristics page, a typical LM317L's output
changes only 7mV (or 0.07% of VOUT = −10V) when a 1W
pulse is applied for 10ms. This performance is thus well inside
the specification limit of 0.2%/W × 1W = 0.2% maximum.
When the 1W pulse is ended, the thermal regulation again
shows a 7mV change as the gradients across the LM317L
www.national.com 6
LM317L
chip die out. Note that the load regulation error of about 14mV
(0.14%) is additional to the thermal regulation error.
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 10μF capacitors have low enough internal
series resistance to deliver 20A spikes when shorted. Al-
though 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 LM317L, this discharge path
is through a large junction that is able to sustain a 2A surge
with no problem. This is not true of other types of positive
regulators. For output capacitors of 25 μF or less, the
LM317L's ballast resistors and output structure limit the peak
current to a low enough level so that there is no need to use
a protection diode.
The bypass capacitor on the adjustment terminal can dis-
charge through a low current junction. Discharge occurs when
either the input or output is shorted. Internal to the LM317L is
a 50Ω resistor which limits the peak discharge current. No
protection is needed for output voltages of 25V or less and
10μF capacitance. Figure 3 shows an LM317L with protection
diodes included for use with outputs greater than 25V and
high values of output capacitance.
906409
D1 protects against C1
D2 protects against C2
FIGURE 3. Regulator with Protection Diodes
LM317L micro SMD Light Sensitivity
Exposing the LM317L micro SMD package to bright sunlight
may cause the VREF to drop. In a normal office environment
of fluorescent lighting the output is not affected. The LM317
micro SMD does not sustain permanent damage from light
exposure. Removing the light source will cause LM317L's
VREF to recover to the proper value.
7 www.national.com
LM317L
Schematic Diagram
906410
www.national.com 8
LM317L
Typical Applications
Digitally Selected Outputs
906411
*Sets maximum VOUT
High Gain Amplifier
906412
Adjustable Current Limiter
906413
12 R1 240
Precision Current Limiter
906414
Slow Turn-On 15V Regulator
906415
Adjustable Regulator with
Improved Ripple Rejection
906416
†Solid tantalum
*Discharges C1 if output is shorted to ground
High Stability 10V Regulator
906417
Adjustable Regulator with Current Limiter
906418
Short circuit current is approximately 600 mV/R3, or 60mA (compared to
LM317LZ's 200mA current limit).
At 25mA output only 3/4V of drop occurs in R3 and R4.
9 www.national.com
LM317L
0V–30V Regulator
906419
Full output current not available at high input-output voltages
Regulator With 15mA Short Circuit Current
906420
Power Follower
906421
Adjusting Multiple On-Card Regulators with Single Control*
906422
*All outputs within ± 100mV
†Minimum load −5mA
www.national.com 10
LM317L
100mA Current Regulator
906423
1.2V–12V Regulator with Minimum Program Current
906424
*Minimum load current 2 mA
50mA Constant Current Battery
Charger for Nickel-Cadmium
Batteries
906425
5V Logic Regulator with Electronic Shutdown*
906426
*Minimum output 1.2V
Current Limited 6V Charger
906427
*Sets peak current, IPEAK = 0.6V/R1
**1000μF is recommended to filter out any input transients.
11 www.national.com
LM317L
Short Circuit Protected 80V Supply
906428
Basic High Voltage Regulator
906429
Q1, Q2: NSD134 or similar
C1, C2: 1μF, 200V mylar**
*Heat sink
www.national.com 12
LM317L
Precision High Voltage Regulator
906430
Q1, Q2: NSD134 or similar
C1, C2: 1μF, 200V mylar**
*Heat sink
**Mylar is a registered trademark of DuPont Co.
Tracking Regulator
906431
A1 = LM301A, LM307, or LF13741 only
R1, R2 = matched resistors with good TC tracking
Regulator With Trimmable Output Voltage
906432
Trim Procedure:
—If VOUT is 23.08V or higher, cut out R3 (if lower, don't cut it out).
—Then if VOUT is 22.47V or higher, cut out R4 (if lower, don't).
—Then if VOUT is 22.16V or higher, cut out R5 (if lower, don't).
This will trim the output to well within ±1% of 22.00 VDC, without any of the
expense or uncertainty of a trim pot (see LB-46). Of course, this technique
can be used at any output voltage level.
13 www.national.com
LM317L
Precision Reference with Short-Circuit Proof Output
906433
*R1–R4 from thin-film network,
Beckman 694-3-R2K-D or similar
1.2V-25 Adjustable Regulator
906401
Full output current not available at high input-output voltages
†Optional—improves transient response
*Needed if device is more than 6 inches from filter capacitors
Fully Protected (Bulletproof)
Lamp Driver
906402
Lamp Flasher
906403
Output rate—4 flashes per second at 10% duty cycle
www.national.com 14
LM317L
Physical Dimensions inches (millimeters) unless otherwise noted
SO-8 Molded Package
NS Package Number M08A
15 www.national.com
LM317L
TO-92 Plastic Package (Z)
NS Package Number Z03A
www.national.com 16
LM317L
NOTE: UNLESS OTHERWISE SPECIFIED.
1. EPOXY COATING
2. 63Sn/37Pb EUTECTIC BUMP.
3. RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD.
4. PIN A1 IS ESTABLISHED BY LOWER LEFT CORNER WITH RESPECT TO TEXT ORIENTATION PINS ARE NUMBERED COUNTERCLOCKWISE.
5. XXX IN DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE X1 IS PACKAGE WIDTH, X2 IS PACKAGE LENGTH AND X3 IS PACKAGE
HEIGHT.
6. REFERENCE JEDEC REGISTRATION MO-211, VARIATION BC.
6-Bump micro SMD
NS Package Number BPA06HPB
X1 = 0.955 X2 = 1.615 X3 =0.850
17 www.national.com
LM317L
NOTE: UNLESS OTHERWISE SPECIFIED.
1. EPOXY COATING
2. 63Sn/37Pb EUTECTIC BUMP.
3. RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD.
4. PIN A1 IS ESTABLISHED BY LOWER LEFT CORNER WITH RESPECT TO TEXT ORIENTATION PINS ARE NUMBERED COUNTERCLOCKWISE.
5. XXX IN DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE X1 IS PACKAGE WIDTH, X2 IS PACKAGE LENGTH AND X3 IS PACKAGE
HEIGHT.
6. REFERENCE JEDEC REGISTRATION MO-211, VARIATION BC.
6-Bump micro SMD
NS Package Number TPA06HPA
X1 = 0.955 X2 = 1.615 X3 =0.500
www.national.com 18
LM317L
Notes
19 www.national.com
LM317L
Notes
LM317L 3-Terminal Adjustable Regulator
For more National Semiconductor product information and proven design tools, visit the following Web sites at:
www.national.com
Products Design Support
Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench
Audio www.national.com/audio App Notes www.national.com/appnotes
Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns
Data Converters www.national.com/adc Samples www.national.com/samples
Interface www.national.com/interface Eval Boards www.national.com/evalboards
LVDS www.national.com/lvds Packaging www.national.com/packaging
Power Management www.national.com/power Green Compliance www.national.com/quality/green
Switching Regulators www.national.com/switchers Distributors www.national.com/contacts
LDOs www.national.com/ldo Quality and Reliability www.national.com/quality
LED Lighting www.national.com/led Feedback/Support www.national.com/feedback
Voltage References www.national.com/vref Design Made Easy www.national.com/easy
PowerWise® Solutions www.national.com/powerwise Applications & Markets www.national.com/solutions
Serial Digital Interface (SDI) www.national.com/sdi Mil/Aero www.national.com/milaero
Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic
PLL/VCO www.national.com/wireless PowerWise® Design
University
www.national.com/training
THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION
(“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY
OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO
SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS,
IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS
DOCUMENT.
TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT
NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL
PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR
APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND
APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE
NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS.
EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO
LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE
AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR
PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY
RIGHT.
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR
SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and
whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected
to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform
can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness.
National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other
brand or product names may be trademarks or registered trademarks of their respective holders.
Copyright© 2010 National Semiconductor Corporation
For the most current product information visit us at www.national.com
National Semiconductor
Americas Technical
Support Center
Email: support@nsc.com
Tel: 1-800-272-9959
National Semiconductor Europe
Technical Support Center
Email: europe.support@nsc.com
National Semiconductor Asia
Pacific Technical Support Center
Email: ap.support@nsc.com
National Semiconductor Japan
Technical Support Center
Email: jpn.feedback@nsc.com
www.national.com