555 Timer

The 555 is a highly stable device designed for generating accurate time delays or oscillations. Additional terminals are provided ' for triggering or resetting. In the time delay mode (monostable mode) the time is set by one external resistor and one capacitor. In the astable (free running) mode the frequency and duty cycle are set by two external resistors and one capacitor. The circuit can be both triggered and reset on falling waveforms. The output circuit can source or sink up to 200mA. TTL circuitry can be driven directly from the output. A dual version of this IC is available, the 556.

Features
• Timing from microseconds to hours

• Adjustable duty cycle
• Sink & source 200mA
• 4-15V operation
• Temperature stability >0.005% per°


Absolute maximum ratings
Supply                                +18V
Power dissipation                600mW





Specifications
Timing Error, monostable Temperature drift                      50ppm/°C
Supply Drift                                                                     0.1 %/V
Timing Error, astable Temperature Drift                            150ppm/°C
Supply Drift                                                                      0.30%/V
Trigger Voltage
Vcc 15V (Itrig = 0.5μA)            5V
Vcc 5V                                     1.67v
Control Voltage
VCC15V                                  10v
VCC 5V                                   3.3v


Special Version of the 555
ICM7555
The ICM 7555 is a CMOS timer IC providing significantly improved performance over the standard 555 timer. At the same time it will act as a direct replacement for this device in most applications. Improved parameters include the low supply current, wide operating supply voltage range, low threshold, trigger and reset currents, no crowbarring of the supply current during any output transition, higher frequency performance and no requirement to decouple the control voltage for stable operation. A dual version of the 7555 is available, the 7556, with two timers sharing only V+(VCC) and V-(GND). They are both capable of sourcing and sinking sufficient current to drive TTL loads and have small enough offset to drive CMOS loads.


Features
• Low supply current (80μA typ)
• Ultra low trigger threshold. (20pA typ)
• High speed operation (500kHz guaranteed)
• Wide supply range 2v to 18v
• No crowbarring of supply during reset.
• Can be used with higher impedance timing elements than 555.
• Complete static protection.


Absolute Maximum Ratings
Supply Voltage              +18v
Input Voltage
Trigger Supply              + 0.3V
Threshold Supply          - 0.3V
Reset control voltage
Output Current            100mA
Power Dissipation       200mW


Specifications
Supply Voltage                                                       2v to 18v
Supply Current                                                       60-120uA
Timing
Initial Accuracy                                                      2.0%
Drift with temperature                                            50ppm/°C
Drift with Supply Voltage                                       1%/V
Trigger Current @ Supply Voltage                         5V 10pA
Reset Current @ Supply Voltage                           5V 20pA
Maximum Oscillator Frequency                             500kHz
Trigger and Threshold Voltages are as for the standard 555.