NE555/SA555/NA555

Document number: DS35112 Rev. 5 - 2

2 of 14

www.diodes.com

February 2021

© Diodes Incorporated

NE555

Pin Descriptions

Pin Name

Pin Number

Description

GND

1

Ground

TRIG

2

Trigger set 1/3VCC

OUT

3

Timer output

RESET

4

Reset active low

CONT

5

External adjustment of internal threshold and trigger voltages

THRES

6

Threshold set to 2/3 VCC

DISCH

7

Low impedance discharge path

VCC

8

Chip supply voltage

Functional Block Diagram

RESET can override TRIG, which can override THRESH

Functional Table

RESET

Nominal Trigger

Voltage

Threshold

Voltage

Output

Discharge

Switch

Low

Irrelevant

Irrelevant

Low

On

High

<1/3VCC

Irrelevant

High

Off

High

>1/3VCC

>2/3VCC

Low

On

High

>1/3VCC

<2/3VCC

As previously established

VCC CONT

RESET

THRES

TRIG

GND

DISCH

OUT

1

2

3

4

5

6

7

8

R1

R2

S

O