1.25 V

IADJ

INPUT

OUTPUT

ADJUST

Over temp

& over

current

protection

+

+

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6

LM337L

SNVS780E – MAY 1998 – REVISED DECEMBER 2016

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Copyright © 1998–2016, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The LM337L devices are adjustable 3-terminal negative-voltage regulators capable of supplying 100 mA over an

output voltage range of –1.2 V to –37 V. They are exceptionally easy to use, requiring only two external resistors

to set the output voltage and one output capacitor for frequency compensation. In addition, LM337L offers full

overload protection. Included on the chip are current limit, thermal overload protection and safe area protection.

All overload protection circuitry remains fully functional even if the adjustment terminal is disconnected. The

LMx37 devices serve a wide variety of applications, including local on-card regulation, programmable output-

voltage regulation, and precision current regulation.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Output Voltage Adjustment

The Adjustment (ADJ) pin serves as a voltage adjustment reference for the output. The ADJ pin can be attached

to a resistor divider circuit to adjust the output voltage level. The reference voltage VADJ will typically be 1.25 V

higher than VO.

7.4 Device Functional Modes

7.4.1 Protection Diodes

When external capacitors are used with any IC regulator, it is sometimes necessary to add protection diodes to

prevent the capacitors from discharging through low current points into the regulator. Most 10-μF capacitors have

low enough internal series resistance to deliver 20-A spikes when shorted. Although the surge is short, there is

enough energy to damage parts of the IC. When an output capacitor is connected to a negative output regulator

and the input is shorted, the output capacitor pulls current out of the output of the regulator. The current depends

on the value of the capacitor, the output voltage of the regulator, and the rate at which VIN is shorted to ground.

The bypass capacitor on the adjustment terminal can discharge through a low current junction. Discharge occurs

when either the input, or the output, is shorted. Figure 15 shows the placement of the protection diodes.