The TLC555-Q1 is a monolithic timing circuit fabricated using the TI
LinCMOS™ process. The timer is fully compatible with CMOS, TTL,
and MOS logic and operates at frequencies up to 2 MHz. Because of its high input impedance, this
device uses smaller timing capacitors than those used by the NE555. As a result, more accurate time
delays and oscillations are possible. Power consumption is low across the full range of
Like the NE555, the TLC555-Q1 has a trigger level equal to approximately one-third of the
supply voltage and a threshold level equal to approximately two-thirds of the supply voltage. These
levels can be altered by use of the control voltage terminal (CONT).
When the trigger input (TRIG) falling below the trigger level sets the flip-flop, and the
output goes high. Having TRIG above the trigger level and the threshold input (THRES) above the
threshold level resets the flip-flop, and the output is low. The reset input (RESET) can override
all other inputs, and a possible use is to initiate a new timing cycle. RESET going low resets the
flip-flop, and the output is low. Whenever the output is low, a low-impedance path exists between
the discharge terminal (DISCH) and GND. Tie all unused inputs to an appropriate logic level to
prevent false triggering.
The advantage of the TLC555-Q1 is that it exhibits greatly reduced supply-current spikes
during output transitions. Although the CMOS output is capable of sinking over 100 mA and sourcing
over 10 mA, the main reason the TLC555-Q1 is able to have low current spikes is due to its edge
rates. This minimizes the need for the large decoupling capacitors required by the NE555.
The TLC555-Q1 is characterized for operation over the full automotive temperature range
of 40°C to 125°C.
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