NE555 waveform generator handle tutorial NE555 internal structure (I)

adopt ne555 Built waveform generator

Square wave can be realized 、 Triangle wave 、 Sine wave output

Project links ：https://pan.baidu.com/s/1T-9bdnO1IrWUsjmRTl12zQ 
Extraction code ：py66

One 、 Chip introduction

 

Parameters

Supply voltage ：4.5-18V

Supply current ：10-15mA

Output current ：225mA (max)

rising / Descent time ：100 ns [3] 

Pin position

ne555 Structure diagram

Pin 1 ( Grounding ) ： Ground wire ( Or common grounding ) , It is usually connected to the common ground of the circuit  [3]  .

Pin 2 ( Trigger point ) ： This foot is the trigger NE555 Make it start its time cycle . The upper edge voltage of the trigger signal must be greater than 2/3 VCC, The lower edge must be lower than 1/3 VCC [3]  .

Pin 3 ( Output ) ： When the time period begins 555 Output pin of , Move to less than the supply voltage 1.7 Volts high potential . At the end of the cycle, the output returns to 0 A low potential of about volts . The maximum output current at high potential is about 200 mA [3]  .

Pin 4 ( Reset ) ： When a low logic potential is sent to this pin, the timer will be reset and the output will return to a low potential . It is usually connected to a positive power supply or ignored  [3]  .

Pin 5 ( control ) ： The external voltage limit is triggered by the external voltage limit pin . When the timer operates in a stable or oscillating mode, this input can be used to change or adjust the output frequency  [3]  .

Pin 6 ( Reset lock ) ： Pin 6 Reset the lock and make the output low . When the voltage of this pin is from 1/3 VCC Move below the voltage 2/3 VCC Start this action when above  [3]  .

Pin 7 ( discharge ) ： This pin has the same current output capability as the main output pin , When Pin3 Low power level ,Pin7 Low resistance to ground （ Ground continuity ）, When Pin3 For high voltage ,Pin7 For high resistance  [3]  .

Pin 8 (V +) ： This is a 555 timer IC The positive supply voltage terminal of . The range of supply voltage is +4.5 Volt ( minimum value ) to +16 Volt ( Maximum ) [3]  

 

Chip internal schematic diagram

 ne555 Analog circuit inside the chip , After visual annotation

Two comparators mainly composed of differential circuits , A voltage dividing circuit composed of three equivalent series resistors , Two reference voltages are provided for the comparator VCC /3 and 2 /3VCC, One RS trigger , A discharge tube T And power output stage .

The simplified digital internal structure diagram is （ The group is composed of or not gates rs trigger ）

 

Logic truth table of chip function realization

 

According to the function table, charging and discharging through the seven corner external capacitor can be achieved 555 Square wave output