SGS Thomson Microelectronics LM338K, LM238K, LM138K Datasheet

ADJUSTABLE VOLTAGE REGULATORS

.GUARANTEED 7A PEAK OUTPUTCURRENT

.GUARANTEED 5A OUTPUTCURRENT

.ADJUSTABLE OUTPUT DOWN TO 1.2V

.LINE REGULATIONTYPICALLY 0.005% /V

.LOAD REGULATION TYPICALLY0.1%

.GUARANTEED THERMAL REGULATION

.CURRENT LIMIT CONSTANT WITH TEM-

PERATURE

.STANDARD3-LEAD TRANSISTOR PACKAGE

DESCRI PTIO N

TheLM138/LM238/LM338 are adjustable 3-terminal
positivevoltageregulatorscapable ofsupplyinginex­cess of 5A over a 1.2V to 32V output range. They are
exceptionally easytouseandrequireonly 2 resistors
tosettheoutput voltage. Careful circuitdesignhasre­sulted in outstanding load and line regulation com­parable to many commercial power supplies. The
LM138familyis supplied in astandard3-leadtransis­torpackage.
A unique featureof the LM138 family is time-de­pendent current limiting. The current limit circuitry
allowspeakcurrents ofupto12Atobedrawnfromthe
regulator for short periods of time. This allows the
LM138 to be used with heavy transient loads and
speedsstart-up underfull-load conditions. Under sus­tainedloading conditions, the currentlimitdecreases
toa safevalueprotectingthe regulator. Also included
on thechip are thermal overload protection and safe
areaprotectionforthepowertransistor.Overloadpro­tection remains functional evenif theadjustment pin
is accidentally disconnected.
Normally,nocapacitorsareneeded unlessthedevice
is situatedfar fromthe input filter capacitors inwhich
case an input bypass is needed. An optional output
capacitor can be added to improve transient res­ponse. The adjustmentterminal can be bypassed to
achieve very highripple rejection ratioswhich aredif­ficulttoachieve withstandard 3-terminal regulators.
Besidesreplacing fixedregulatorsordiscretedesigns,
theLM238is usefulin awide varietyof other applica­tions. Since the regulator is ”floating” and sees only
theinput-to-outputdifferential voltage,suppliesofsev­eral hundred volts can be regulated as long as the
maximuminputto inputdifferential isnotexceeded.

TheLM138/LM238/LM338 arepackaged in standard
steelTO-3 transistor packages. The LM138 is rated
foroperation from -55oCto150oC, the LM238from
–25°C to + 150°C and the LM338 from 0°Cto+
125°C.

THREE-TERMINAL 5-A

ORDER CODE

PART

NUMBER

LM138
LM238
LM338

EXAMPLE: LM138K

PIN CONNE C TI ON

LM13 8/2 38

TO3

K SUFFIX

(SteelCan)

TEMPERATURE

RANGE

o

-55

C to + 150oC

o

-25

C to + 150oC

0oC to + 125oC

(bot tom view)

Caseis output

LM338

PACKAGE

K

•

•

•

March1993

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LM138-LM238-LM338

ABSOLUTE MAXIMUM RATING

Symbol Parameter Value Unit

P

Power Dissipation Internally Limited W

tot

V

T

T

THERMAL CHARACTERISTICS

Input-Output Voltage DIfferential 35 V

I-VO

Operating Junction Temperature Range LM138

oper

LM238
LM338

Storage Temperature Range -65 to 150

T

stg

Lead Temperature (Soldering, 10 seconds) 300

lead

-55 to 150

-25 to 150
0 to 125

o

C

o

C

o

C

Symbol Parameter Value Unit

R
R

Typical Junction-Case Thermal Resistance 1.4

th(j-c)

Max Junction-Ambient Thermal Resistance 35

th(j-a)

o

C/W

o

C/W

SCHEM ATIC DIAG RA M

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LM138-LM238-LM338

ELECTRICAL CHARACTERISTICS
LM138: -55 ≤ Tj≤ 150oC, VI-VO= 5V, IO=2.5A
LM238: -25 ≤ Tj≤ 150oC, VI-VO= 5V, IO=2.5A
LM338: 0 ≤ Tj≤ 150oC, VI-VO= 5V, IO= 2.5A

Although power dissipation is internally limited, these specifications apply to power dissipation up to
50W (unless otherwise specified).

Symbol Parameter LM138-LM238 LM338 Unit

Min. Typ. Max. Min. Typ. Max.

Line Regulation - (note 1)

K

VI

T

=25oC, 3 V ≤ (VI-VO)≤35 V

amb

Load Regulation T

K

VO

=25oC, 10 mA ≤ IO≤ 5A

amb

VO≤5V - (note 1)
VO≥ 5V - (note 1)

Thermal Regulation (pulse = 20 ms) 0.002 0.01 0.002 0.02 %/W
Adjustment Pin Current 45 100 45 100 µA

I

adj

∆I

Adjustment Pin Current Change

adj

10 mA ≤ IL≤ 5A,3V≤(VI-VO)≤35 V

v

Reference Voltage

(ref)

3V ≤ (VI-VO)≤35 V, 10 mA ≤ IO≤ 5A, P ≤ 50W
Line Regulation - (note 1)

K

VI

3V≤(VI-VO)≤35 V
Load Regulation 10 mA ≤ IO≤ 5A

K

VO

VO≤5V - (note 1)
VO≥ 5V - (note 1)

K

Temperature Stability (T

VT

I

O(min)

I

O(max)

Minimum Load Current (VI-VO≤35 V) 3.5 5 3.5 10 mA
Current Limit (VI-VO≤10 V)

min

≤ Tj≤ T

)11%

max

DC

0.5 ms Peak
V

=30V

I-VO

RMS Output Noise, % of V
(T

=25oC, 10 Hz ≤ f ≤ 10 KHz)

amb

Ripple Rejection Ratio

R

vf

O

VO= 10 V, f = 120 Hz
C

=10µF60

adi

Long Term Stability (T

K

VH

Note 1 : Regulation is measured at constant junction temperature. Changes in output voltage due to heating effects are taken
into account separately by thermal rejection.

= 125oC) 0.3 1 0.3 1 %

amb

0.005 0.01 0.005 0.03 %/V

5

0.1150.3

5

0.1250.5

mV

0.2 5 0.2 5 µA

1.19 1.24 1.29 1.19 1.24 1.29 V

0.02 0.04 0.02 0.06 %/V

5
7

20

0.3300.6

8

12

1

20

0.3

5
7

12

50

mV

1

8
1

0.003 0.003 %

60
75 60

60
75

%

%

A

dB

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LM138-LM238-LM338

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