LM138 datasheet(1/23 Pages) STMICROELECTRONICS

部件名	LM138

功能描述	Three-terminal 5 A adjustable voltage regulators

PDF	23 Pages

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制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

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1 / 23 page

April 2008

Rev 2

1/23

23

LM138 - LM238 - LM338

Three-terminal 5 A adjustable voltage regulators

Features

■ Guaranteed 7 A peak output current

■ Guaranteed 5 A output current

■ Adjustable output down to 1.2 V

■ Line regulation typically 0.005 %/V

■ Load regulation typically 0.1 %

■ Guaranteed thermal regulation

■ Current limit constant with temperature

■ Standard 3-lead transistor package

Description

The LM138, LM238, LM338 are adjustable 3-

terminal positive voltage regulators 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-de-

pendent 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 pin is accidentally disconnected.

Normally, no capacitors are needed unless the

device is situated far 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 which are

difficult to achieve with standard 3-terminal

regulators.

Besides replacing fixed regulators or discrete

designs, the LM238 is useful in a wide variety of

other applications. Since the regulator is "floating"

and sees only the input-to-output differential

voltage, supplies of several hundred volts can be

regulated as long as the maximum input to input

differential is not exceeded.

The LM138, LM238, LM338 are packaged in

standard steel TO-3 transistor package. The

LM138 is rated for operation from - 55 °C to

150 °C, the LM238 from - 25 °C to 150 °C and the

LM338 from 0 °C to 125 °C.

TO-3

Table 1.

Device summary

Part numbers

Order codes

Temperature range

LM138

LM138K

-55 °C to 150 °C

LM238

LM238K

-25 °C to 150 °C

LM338

LM338K

0 °C to 125 °C

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类似零件编号 - LM138

制造商	部件名	数据表	功能描述
National Semiconductor ...	LM138	396Kb / 16P	5-Amp Adjustable Regulators
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Seme LAB	LM138	56Kb / 6P	5 AMP POSITIVE ADJUSTABLE VOLTAGE REGULATOR
Linear Technology	LM138	185Kb / 12P	5A Positive Adjustable Voltage Regulator
Linear Technology	LM138	148Kb / 12P	5A Positive Adjustable Voltage Regulator

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