COMPARATOR

TRIGGER

FLIP FLOP

COMPARATOR

RESET

+Vcc

DISCHARGE

THRESHOLD

OUTPUT

STAGE

CONTROL

VOLTAGE

OUTPUT

8

LM555-MIL

SNAS745 – JUNE 2017

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7 Detailed Description

7.1 Overview

The LM555-MIL is a highly stable device for generating accurate time delays or oscillation. Additional terminals

are provided for triggering or resetting if desired. In the time delay mode of operation, the time is precisely

controlled by one external resistor and capacitor. For astable operation as an oscillator, the free running

frequency and duty cycle are accurately controlled with two external resistors and one capacitor. The circuit may

be triggered and reset on falling waveforms, and the output circuit can source or sink up to 200 mA or driver TTL

circuits. The LM555-MIL are available in 8-pin PDIP, SOIC, and VSSOP packages and is a direct replacement

for SE555/NE555.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Direct Replacement for SE555/NE555

The LM555-MIL timer is a direct replacement for SE555 and NE555. It is pin-to-pin compatible so that no

schematic or layout changes are necessary. The LM555-MIL come in an 8-pin PDIP, SOIC, and VSSOP

package.

7.3.2 Timing From Microseconds Through Hours

The LM555-MIL has the ability to have timing parameters from the microseconds range to hours. The time delay

of the system can be determined by the time constant of the R and C value used for either the monostable or

astable configuration. A nomograph is available for easy determination of R and C values for various time delays.

7.3.3 Operates in Both Astable and Monostable Mode

The LM555-MIL can operate in both astable and monostable mode depending on the application requirements.

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Monostable mode: The LM555-MIL timer acts as a “one-shot” pulse generator. The pulse beings when the