GENERAL DESCRIPTION

The ALD555 timer is a high performance monolithic timing circuit built

with advanced silicon gate CMOS technology. It offers the benefits of

high input impedance, thereby allowing smaller timing capacitors and

longer timing cycle; high speed, with typical cycle time of 500ns; low

power dissipation for battery operated environment; reduced supply

current spikes, allowing smaller and lower cost decoupling capacitors.

It is capable of producing accurate time delays and oscillations in both

monostable and astable operation. It operates in the one-shot (monostable)

mode or 50 duty cycle free running oscillation mode with a

single resistor and one capacitor. The inputs and outputs are fully

compatible with CMOS, NMOS or TTL logic.

There are three matched internal resistors (approximately 200KΩ

each) that set the threshold and trigger levels at two-thirds and onethird

respectively of V+. These levels can be adjusted by using the

control terminal (pin 5). When the trigger input is below the trigger level,

the output is in the high state and sourcing 2mA. When threshold input

is above the threshold level at the same time the trigger input is above

the trigger level, the internal flip-flop is reset, the output goes to the low

state and sinks up to 10mA. The reset input overrides all other inputs

and when it is active (reset voltage less than 1V), the output is in the

low state.

FEATURES

• Functional equivalent to NE555 with greatly expanded high

and low frequency ranges

• High speed, low power, monolithic CMOS technology

• Low supply current: 100µA typical

• Extremely low trigger, threshold and reset currents:1pA typical

• High speed operation -- 2MHz oscillation

• Low operating supply voltage of 2 to 12V

• Operates in both monostable and astable modes

• Fixed 50 duty cycle or adjustable duty cycle

• CMOS, NMOS and TTL compatible input/output

• High discharge sinking current of 80mA

• Low supply current spikes

APPLICATIONS

• High speed one-shot (monostable)

pulse generation

• Precision timing

• Sequential timing

• Long delay timer

• Pulse width and pulse position

modulation

• Missing pulse detector

• Frequency divider