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