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LM338-MIL

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SNVSAX2 – JUNE 2017

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7 Detailed Description

7.1 Overview

The LM338 device is an adjustable, three-terminal, positive-voltage regulator 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.

The device 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 LM338 device is versatile in its 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 LM338

device 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

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

output voltage.