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3. Input

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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.

LM138

LM338

SNVS771C –MAY 1998–REVISED DECEMBER 2016

LM138 and LM338 5-Amp Adjustable Regulators

1 Features

1• Specified 7-A Peak Output Current

• Specified 5-A Output Current

• Adjustable Output Down to 1.2 V

• Specified Thermal Regulation

• Current Limit Constant With Temperature

• P +Product Enhancement Tested

• Output is Short-Circuit Protected

2 Applications

• Adjustable Power Supplies

• Constant Current Regulators

• Battery Chargers

Available Packages

Typical Application Circuit

3 Description

The LM138 series of adjustable 3-terminal positive

voltage regulators is capable of supplying in excess

of 5 A over a 1.2-V to 32-V output range. They are

exceptionally easy to use and require only 2 resistors

to set the output voltage. Careful circuit design has

resulted in outstanding load and line regulation,

comparable to many commercial power supplies. The

LM138 family is supplied in a standard 3-lead

transistor package.

A unique feature of the LM138 family is time-

dependent current limiting. The current limit circuitry

allows peak currents of up to 12 A to be drawn from

the regulator for short periods of time. This allows the

LM138 to be used with heavy transient loads and

speeds start-up under full-load conditions. Under

sustained loading conditions, the current limit

decreases to a safe value protecting the regulator.

Also included on the chip are thermal overload

protection and safe area protection for the power

transistor. Overload protection remains functional

even if the adjustment (ADJ) pin is accidentally

disconnected.

Normally, 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 output capacitor can be added to improve

transient response, while bypassing the adjustment

pin increases the ripple rejection of the regulator.

Besides replacing fixed regulators or discrete

designs, the LM138 is useful in a wide variety of

other applications. Because the regulator is floating

and receives 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; do not short-circuit output

to ground. The part numbers in the LM138 series

which have a Ksuffix are packaged in a standard

steel TO-CAN package, while those with a Tsuffix

are packaged in a TO-220 plastic package. The

LM138 is rated for TJ= –55°C to 150°C, and the

LM338 is rated for TJ= 0°C to 125°C.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)

LM138 TO-CAN (2) 25.40 mm × 38.94 mm

LM338 TO-220 (3) 10.16 mm × 14.986 mm

TO-CAN (2) 25.40 mm × 38.94 mm

(1) For all available packages, see the orderable addendum at

the end of the data sheet.

LM138

LM338

SNVS771C –MAY 1998–REVISED DECEMBER 2016

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Product Folder Links: LM138 LM338

Table of Contents

1 Features.................................................................. 1

2 Applications ........................................................... 1

3 Description............................................................. 1

4 Revision History..................................................... 2

5 Pin Configuration and Functions......................... 3

6 Specifications......................................................... 3

6.1 Absolute Maximum Ratings ...................................... 3

6.2 Recommended Operating Conditions....................... 3

6.3 Thermal Information.................................................. 4

6.4 Electrical Characteristics: LM138.............................. 4

6.5 Electrical Characteristics: LM338.............................. 5

6.6 Typical Characteristics.............................................. 6

7 Detailed Description.............................................. 9

7.1 Overview................................................................... 9

7.2 Functional Block Diagram......................................... 9

7.3 Feature Description................................................... 9

7.4 Device Functional Modes........................................ 10

8 Application and Implementation ........................ 11

8.1 Application Information............................................ 11

8.2 Typical Applications ................................................ 12

8.3 System Examples ................................................... 17

9 Power Supply Recommendations...................... 23

10 Layout................................................................... 23

10.1 Layout Guidelines ................................................. 23

10.2 Layout Example .................................................... 23

11 Device and Documentation Support................. 24

11.1 Receiving Notification of Documentation Updates 24

11.2 Related Links ........................................................ 24

11.3 Community Resources.......................................... 24

11.4 Trademarks........................................................... 24

11.5 Electrostatic Discharge Caution............................ 24

11.6 Glossary................................................................ 24

12 Mechanical, Packaging, and Orderable

Information........................................................... 24

4 Revision History

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

Changes from Revision B (April 2013) to Revision C Page

• Added Device Information table, Pin Configuration and Functions section, Specifications section, Recommended

Operating Conditions table, Thermal Information table, Detailed Description section, Application and Implementation

section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and

Mechanical, Packaging, and Orderable Information section.................................................................................................. 1

• Deleted RETS138K military specification reference from Absolute Maximum Ratings table................................................. 3

• Changed Junction to Ambient, RθJA, value in Thermal Information table From: 50°C/W To: 22.9°C/W (NDE)..................... 4

• Changed Junction to Case, RθJC(top), value in Thermal Information table From: 4°C/W To: 15.7°C/W (NDE)....................... 4

Changes from Revision A (April 2013) to Revision B Page

• Changed layout of National Semiconductor Data Sheet to TI format .................................................................................... 1

LM138

LM338

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5 Pin Configuration and Functions

NDS Package

2-Pin TO-CAN

Bottom View

Package Number NDS0002A

NDE Package

3-Pin TO-220

Front View

Package Number NDE0003B

Pin Functions

PIN I/O DESCRIPTION

NAME TO-220 TO-CAN

ADJ 1 1 I Output voltage adjustment pin. Connect to a resistor divider to set VO

VIN 3 2 I Supply input pin

VOUT 2 Case O Voltage output pin

(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.

6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)(1)

MIN MAX UNIT

Input and output voltage differential –0.3 40 V

Power dissipation Internally limited

Lead temperature TO-3 package (soldering, 10 s) 300 °C

TO-220 package (soldering, 4 s) 260

Operating temperature, TJLM138 –55 150 °C

LM338 0 125

Storage temperature, Tstg –65 150 °C

6.2 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted) MIN MAX UNIT

Input-to-output voltage differential 3 40 V

Output current 5 A

LM138

LM338

SNVS771C –MAY 1998–REVISED DECEMBER 2016

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

report.

6.3 Thermal Information

THERMAL METRIC(1) LM338 LM338

UNITNDS (TO-CAN) NDE (TO-220) NDS (TO-CAN)

2 PINS 3 PINS 2 PINS

RθJA Junction-to-ambient thermal resistance 35 22.9 35 °C/W

RθJC(top) Junction-to-case (top) thermal resistance 1 15.7 1 °C/W

RθJB Junction-to-board thermal resistance — 4.1 — °C/W

ψJT Junction-to-top characterization parameter — 2.1 — °C/W

ψJB Junction-to-board characterization parameter — 4.1 — °C/W

RθJC(bot) Junction-to-case (bottom) thermal resistance — 0.7 — °C/W

(1) These specifications are applicable for power dissipations up to 50 W for the TO-3 (NDS) package and 25 W for the TO-220 (NDE)

package. Power dissipation is specified at these values up to 15-V input-output differential. Above 15-V differential, power dissipation is

limited by internal protection circuitry. All limits (that is, the numbers in the minimum and maximum columns) are specified to TI's AOQL

(Average Outgoing Quality Level).

(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.

6.4 Electrical Characteristics: LM138

Values apply for TJ= 25°C; VIN – VOUT = 5 V; and IOUT = 10 mA (unless otherwise noted).(1)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

VREF Reference voltage 3 V ≤(VIN – VOUT)≤35 V, 10 mA ≤IOUT ≤5 A, P ≤50 W,

TJ= –55°C to 150°C 1.19 1.24 1.29 V

VRLINE Line regulation 3 V ≤(VIN – VOUT)≤35 V(2) TJ= 25°C 0.005% 0.01% V

TJ= –55°C to 150°C 0.02% 0.04% V

VRLOAD Load regulation 10 mA ≤IOUT ≤5 A(2) TJ= 25°C 0.1% 0.3%

TJ= –55°C to 150°C 0.3% 0.6%

Thermal regulation 20 ms pulse 0.002% 0.01% W

IADJ Adjustment pin current TJ= –55°C to 150°C 45 100 µA

ΔIADJ Adjustment pin current change 10 mA ≤IOUT ≤5 A, 3 V ≤(VIN – VOUT)≤35 V,

TJ= –55°C to 150°C 0.2 5 µA

ΔVR/T Temperature stability TJ= –55°C to 150°C 1%

ILOAD(MIN) Minimum load current VIN – VOUT = 35 V, TJ= –55°C to 150°C 3.5 5 mA

ICL Current limit

VIN – VOUT ≤10 V

DC, TJ= –55°C to 150°C 5 8 A

0.5-ms peak, TJ= –55°C to 150°C 7 12 A

VIN – VOUT = 30 V 1 1 A

VNRMS output noise

(percent of VOUT)10 Hz ≤f≤10 kHz 0.003%

ΔVR/ΔVIN Ripple rejection ratio

VOUT = 10 V, f = 120 Hz, CADJ = 0 µF,

TJ= –55°C to 150°C 60 dB

VOUT = 10 V, f = 120 Hz, CADJ = 10 µF,

TJ= –55°C to 150°C 60 75 dB

Long-term stability TJ= 125°C, 1000 Hrs 0.3% 1%

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LM338

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(1) These specifications are applicable for power dissipations up to 50 W for the TO-3 (NDS) package and 25 W for the TO-220 (NDE)

package. Power dissipation is specified at these values up to 15-V input-output differential. Above 15-V differential, power dissipation is

limited by internal protection circuitry. All limits (that is, the numbers in the minimum and maximum columns) are specified to TI's AOQL

(Average Outgoing Quality Level).

(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.

6.5 Electrical Characteristics: LM338

Values apply for TJ= 25°C; VIN – VOUT = 5 V; and IOUT = 10 mA (unless otherwise noted).(1)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

VREF Reference voltage 3 V ≤(VIN – VOUT)≤35 V, 10 mA ≤IOUT ≤5 A, P ≤50 W,

TJ= 0°C to 125°C 1.19 1.24 1.29 V

VRLINE Line regulation 3 V ≤(VIN – VOUT)≤35 V(2) TJ= 25°C 0.005% 0.03% V

TJ= 0°C to 125°C 0.02% 0.06% V

VRLOAD Load regulation 10 mA ≤IOUT ≤5 A(2) TJ= 25°C 0.1 0.5

TJ= 0°C to 125°C 0.3 1

Thermal regulation 20-ms pulse 0.002% 0.02% W

IADJ Adjustment pin current TJ= 0°C to 125°C 45 100 µA

ΔIADJ Adjustment pin current change 10 mA ≤IOUT ≤5 A, 3 V ≤(VIN – VOUT)≤35 V,

TJ= 0°C to 125°C 0.2 5 µA

ΔVR/T Temperature stability TJ= 0°C to 125°C 1

ILOAD(MIN) Minimum load current VIN – VOUT = 35 V, TJ= 0°C to 125°C 3.5 10 mA

ICL Current limit

VIN – VOUT ≤10 V

DC, TJ= 0°C to 125°C 5 8 A

0.5-ms peak, TJ= 0°C to 125°C 7 12 A

VIN – VOUT = 30 V 1 A

VNRMS output noise

(percent of VOUT)10 Hz ≤f≤10 kHz 0.003%

ΔVR/ΔVIN Ripple rejection ratio

VOUT = 10 V, f = 120 Hz, CADJ = 0 µF,

TJ= 0°C to 125°C 60 dB

VOUT = 10 V, f = 120 Hz, CADJ = 10 µF,

TJ= 0°C to 125°C 60 75 dB

Long-term stability TJ= 125°C, 1000 Hrs 0.3% 1%

LM138

LM338

SNVS771C –MAY 1998–REVISED DECEMBER 2016

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6.6 Typical Characteristics

Figure 1. Current Limit Figure 2. Current Limit

Figure 3. Current Limit Figure 4. Load Regulation

Figure 5. Dropout Voltage Figure 6. Adjustment Current

LM138

LM338

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Typical Characteristics (continued)

Figure 7. Temperature Stability Figure 8. Output Impedance

Figure 9. Minimum Operating Current Figure 10. Ripple Rejection

Figure 11. Ripple Rejection Figure 12. Ripple Rejection

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LM338

SNVS771C –MAY 1998–REVISED DECEMBER 2016

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Typical Characteristics (continued)

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

LM138

LM338

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7 Detailed Description

7.1 Overview

The LM138 and LM338 devices are adjustable, three-terminal, positive-voltage regulators capable of supplying

more than 5 A over an output-voltage range of 1.2 V to 32 V. It requires only two external resistors to set the

output voltage. These devices feature a typical line regulation of 0.005% and typical load regulation of 0.1%. It

includes time-dependent current limiting, thermal overload protection, and safe operating area protection.

Overload protection remains functional even if the ADJUST terminal is disconnected.

The LM138 and LM338 devices are versatile in their applications, including uses in programmable output

regulation and local on-card regulation. Or, by connecting a fixed resistor between the ADJUST and OUTPUT

terminals, the LM138 and LM338 devices can function as a precision current regulators. An optional output

capacitor can be added to improve transient response. The ADJUST terminal can be bypassed to achieve very

high ripple-rejection ratios, which are difficult to achieve with standard three-terminal regulators.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 NPN Darlington Output Drive

NPN Darlington output topology provides naturally low output impedance and an output capacitor is optional. To

support maximum current and lowest temperature, 3-V headroom is recommended (VI– VO).

7.3.2 Overload Block

Overcurrent and overtemperature shutdown protects the device against overload or damage from operating in

excessive heat.

7.3.3 Programmable Feedback

Op amp with 1.25-V offset input at the ADJUST terminal provides easy output voltage or current (not both)

programming. For current regulation applications, a single resistor whose resistance value is 1.25 V/IO and

power rating is greater than 1.25 V2/R must be used. For voltage regulation applications, two resistors set the

output voltage.

LM138

LM338

SNVS771C –MAY 1998–REVISED DECEMBER 2016

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Product Folder Links: LM138 LM338

7.4 Device Functional Modes

7.4.1 Normal Operation

The device OUTPUT pin sources current necessary to make OUTPUT pin 1.25 V greater than ADJUST terminal

to provide output regulation.

7.4.2 Operation With Low Input Voltage

The device requires up to 3-V headroom (VI– VO) to operate in regulation. With less headroom, the device may

drop out and OUTPUT voltage is INPUT voltage minus drop out voltage.

7.4.3 Operation at Light Loads

The device passes its bias current to the OUTPUT pin. The load or feedback must consume this minimum

current for regulation or the output may be too high. A 250-Ωfeedback resistor between OUTPUT and ADJUST

consumes the worst case minimum load current of 5 mA.

7.4.4 Operation in Self Protection

When an overload occurs, the device shuts down Darlington NPN output stage or reduces the output current to

prevent device damage. The device automatically resets from the overload. The output may be reduced or

alternate between on and off until the overload is removed.

OUT REF ADJ

R 2

V = V 1+ + I R 2

R 2

æ ö

ç ÷

è ø

LM138

LM338

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SNVS771C –MAY 1998–REVISED DECEMBER 2016

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8 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.

8.1 Application Information

In operation, the LM138 develops a nominal 1.25-V reference voltage (VREF) between the output and adjustment

terminal. The reference voltage is impressed across program resistor R1and, since the voltage is constant, a

constant current I1then flows through the output set resistor R2, giving an output voltage calculated with

Equation 1.

(1)

Figure 15. Typical Application Circuit

Because the 50-µA current from the adjustment terminal represents an error term, the LM138 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 rises.

LM138

LM338

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8.2 Typical Applications

8.2.1 Constant 5-V Regulator

Figure 16. Constant 5-V Regulator

8.2.1.1 Design Requirements

R1: Because the LM138 produces a typical 1.24 V potential between the OUTPUT and ADJUST pins, placing a

270-Ωresistor between them causes 4.6 mA to flow through R1 and R2.

R2: To achieve a 5-V output, the sum of the voltages across R1 and R2 must equal 5 V. Therefore, Vr2 must

equal 3.76 V when 4.6 mA is flowing through it. R2 = Vr2 / I = 3.76 V / 4.6 mA = ~820 Ω.

CIN: 0.1 µF of input capacitance helps filter out unwanted noise, especially if the regulator is located far from the

power supply filter capacitors.

COUT: The regulator is stable without any output capacitance, but adding a 1-µF capacitor improves the transient

response.

CADJ: A 10-µF capacitor bypassing the ADJUST pin to ground improves the regulators ripple rejection.

D1: Protection diode D1 is recommended if COUT is used. The diode provides a low-impedance discharge path to

prevent the capacitor from discharging into the output of the regulator (see Protection Diodes).

D2: Protection diode D2 is recommended if CADJ is used. The diode provides a low-impedance discharge path to

prevent the capacitor from discharging into the output of the regulator (see Protection Diodes).

Table 1 lists the design parameters for this typical application.

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LM338

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Table 1. Design Parameters

PARAMETER VALUE

Feedback resistor 1 (R1) 270 Ω

Feedback resistor 2 (R2) 820 Ω

Input capacitor (CIN) 0.1 µF

Output capacitor (COUT) 1 µF

Adjust capacitor(CADJ) 10 µF

8.2.1.2 Detailed Design Procedure

8.2.1.2.1 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 eliminate the possibility of problems.

The adjustment terminal can be bypassed to ground on the LM138 to improve ripple rejection. This bypass

capacitor prevents ripple from being amplified as the output voltage is increased. With a 10-µF bypass capacitor,

75-dB ripple rejection is obtainable at any output level. Increases over 20 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 are 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; but 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 LM138 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.

8.2.1.2.2 Load Regulation

The LM138 is capable of providing extremely good load regulation but a few precautions are needed to obtain

maximum performance. The current set resistor connected between the adjustment terminal and the output

terminal (usually 240 Ω) must be tied directly to the output of the regulator (case) rather than near the load. This

eliminates line drops from appearing effectively in series with the reference and degrading regulation. For

example, a 15-V regulator with 0.05-Ωresistance between the regulator and load has a load regulation due to

line resistance of 0.05 Ω× IL. If the set resistor is connected near the load, the effective line resistance is 0.05 Ω

(1 + R2/R1) or in this case, 11.5 times worse.

Figure 17 shows the effect of resistance between the regulator and 240-Ωset resistor.

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LM338

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Figure 17. 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 2

separate leads to the case. The ground of R2 can be returned near the ground of the load to provide remote

ground sensing and improve load regulation.

8.2.1.2.3 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 20-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 discharges

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 LM138 this discharge path is through a large junction that

is able to sustain 25-A surge with no problem. This is not true of other types of positive regulators. For output

capacitors of 100 µF or less at output of 15 V 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 output is shorted. Internal to the LM138 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 18

shows an LM138 with protection diodes included for use with outputs greater than 25 V and high values of output

capacitance.

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D1 protects against C1

D2 protects against C2

Figure 18. Regulator With Protection Diodes

8.2.1.3 Application Curves

Figure 19. Regulator Start-Up Figure 20. Regulator Shutdown

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Figure 21. Regulator Response to Load Step

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8.3 System Examples

Figure 22. Regulator and Voltage Reference Figure 23. 1.2-V to 25-V Adjustable Regulator

Full output current not available at high input-output voltages

†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.

*Needed if device is more than 6 inches from filter capacitors.

**R1 = 240 Ωfor LM138. R1, R2 as an assembly can be ordered

from Bourns:

MIL part no. 7105A-AT2-502

COMM part no. 7105A-AT7-502

* Adjust for 3.75 across R1

Figure 24. Temperature Controller Figure 25. Precision Power Regulator With

Low Temperature Coefficient

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System Examples (continued)

†Solid tantalum

*Discharges C1 if output is shorted to ground

**R1 = 240 Ωfor LM138

Figure 26. Slow Turnon 15-V Regulator Figure 27. Adjustable Regulator With

Improved Ripple Rejection

*Sets maximum VOUT

**R1 = 240 Ωfor LM138

Figure 28. High Stability 10-V Regulator Figure 29. Digitally Selected Outputs

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System Examples (continued)

* Minimum load—100 mA

** Minimum output ≈1.2 V

Figure 30. 15-A Regulator Figure 31. 5-V Logic Regulator With

Electronic Shutdown**

* R1 = 240 Ω, R2 = 5k for LM138

Full output current not available at high input-output voltages

Figure 32. Light Controller Figure 33. 0 to 22-V Regulator

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System Examples (continued)

Figure 34. 12-V Battery Charger Figure 35. Adjustable Current Regulator

Figure 36. Precision Current Limiter Figure 37. 5-A Current Regulator

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LM338

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System Examples (continued)

† Minimum load—10 mA

* All outputs within ±100 mV

Figure 38. Tracking Preregulator Figure 39. Adjusting Multiple On-Card Regulators

With Single Control*

AV= 1, RF= 10k, CF= 100 pF

AV= 10, RF= 100k, CF= 10 pF

Bandwidth ≥100 kHz

Distortion ≤0.1%

Use of RSallows low charging rates with fully charged battery.

**The 1000 µF is recommended to filter out input transients

Use of RSallows low charging rates with fully charged battery.

**The 1000 µF is recommended to filter out input transients

Figure 40. Power Amplifier Figure 41. Simple 12-V Battery Charger

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System Examples (continued)

* Set max charge current to 3 A

** THE 1000 µF is recommended to filter out input transients.

Figure 42. Adjustable 15-A Regulator Figure 43. Current Limited 6-V Charger

* Minimum load—100 mA

Figure 44. 10-A Regulator

LM138

LM338

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9 Power Supply Recommendations

The input supply to LM138 and LM338 must be kept at a voltage level such that its maximum input to output

differential voltage rating is not exceeded. The minimum dropout voltage must also be met with extra headroom

when possible to keep the LM138 and LM338 in regulation. TI recommends a capacitor be placed at the input to

bypass noise.

10 Layout

10.1 Layout Guidelines

Some layout guidelines must be followed to ensure proper regulation of the output voltage with minimum noise.

Traces carrying the load current must be wide to reduce the amount of parasitic trace inductance and the

feedback loop from VOUT to ADJ must be kept as short as possible. To improve PSRR, a bypass capacitor can

be placed at the ADJ pin and must be placed as close as possible to the IC. In cases when VIN shorts to ground,

an external diode must 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 must be placed from ADJ to VOUT to provide a path for the bypass capacitor to

discharge. These diodes must be placed close to the corresponding IC pins to increase their effectiveness.

10.2 Layout Example

Figure 45. LMx38 Layout

LM138

LM338

SNVS771C –MAY 1998–REVISED DECEMBER 2016

www.ti.com

Product Folder Links: LM138 LM338

11 Device and Documentation Support

11.1 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.

11.2 Related Links

The table below lists quick access links. Categories include technical documents, support and community

resources, tools and software, and quick access to sample or buy.

Table 2. Related Links

PARTS PRODUCT FOLDER SAMPLE & BUY TECHNICAL

DOCUMENTS TOOLS &

SOFTWARE SUPPORT &

COMMUNITY

LM138 Click here Click here Click here Click here Click here

LM338 Click here Click here Click here Click here Click here

11.3 Community Resources

The following links connect to TI community resources. Linked contents are 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.

TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration

among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help

solve problems with fellow engineers.

Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and

contact information for technical support.

11.4 Trademarks

E2E is a trademark of Texas Instruments.

All other trademarks are the property of their respective owners.

11.5 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.

11.6 Glossary

SLYZ022 —TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.

12 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 6-Feb-2020

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead/Ball Finish

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LM138K STEEL ACTIVE TO-3 NDS 2 50 TBD Call TI Call TI -55 to 125 LM138K

STEELP+

LM138K STEEL/NOPB ACTIVE TO-3 NDS 2 50 Green (RoHS

& no Sb/Br) Call TI Level-1-NA-UNLIM -55 to 125 LM138K

STEELP+

LM338T NRND TO-220 NDE 3 45 TBD Call TI Call TI 0 to 125 LM338T P+

LM338T/NOPB ACTIVE TO-220 NDE 3 45 Green (RoHS

& no Sb/Br) SN Level-1-NA-UNLIM 0 to 125 LM338T 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".

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/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish 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.

PACKAGE OPTION ADDENDUM

www.ti.com 6-Feb-2020

Addendum-Page 2

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.

MECHANICAL DATA

NDE0003B

www.ti.com

MECHANICAL DATA

NDS0002A

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