(

)

OUT

ADJ

R

V

V

I

R

2

1.25

1

2

120

æ

ö

-

= -

+

+ -

´

ç

÷

è

ø

LM137, LM337-N

SNVS778E – MAY 1999 – REVISED JANUARY 2016

www.ti.com

7 Detailed Description

7.1 Overview

In operation, the LM137 and LM337-N develops a nominal

−1.25-V reference voltage between the output and

adjustment terminal. The reference voltage is impressed across program resistor R1 (120

Ω for example) and,

because the voltage is constant, a constant current then flows through the output set resistor R2, giving an

output voltage calculated by Equation 1.

(1)

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Thermal Regulation

When power is dissipated in an IC, a temperature gradient occurs across the IC chip affecting the individual IC

circuit components. With an IC regulator, this gradient can be especially severe because power dissipation is

large. Thermal regulation is the effect of these temperature gradients on output voltage (in percentage output

change) per Watt of power change in a specified time. Thermal regulation error is independent of electrical

regulation or temperature coefficient, and occurs within 5 ms to 50 ms after a change in power dissipation.

Thermal regulation depends on IC layout as well as electrical design. The thermal regulation of a voltage

applied. The LM137 device's specification is 0.02%/W, maximum.

8

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