LM138QML datasheet(12/34 Pages) TI1

12 / 34 page

LM138QML

ADJ

VIN

VOUT

IADJ

VREF

VOUT

LM138QML

SNVSAA9 – OCTOBER 2017

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Product Folder Links: LM138QML

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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 LM138QML device develops a nominal 1.25-V 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:

(1)

Because the 50-μA current from the adjustment terminal represents an error term, the LM138QML 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.

LM138QML Datasheet(PDF) 12 Page - Texas Instruments