Low-Power Dual LinCMOS™ Timer

The TLC556 series are CMOS monolithic

timing circuits. The timers are fully compatible with CMOS, TTL, and MOS logic and

operates at frequencies up to 2MHz. Because of high input impedance, this device

supports smaller timing capacitors than those supported by the NE556. As a result,

more accurate time delays and oscillations are possible. Power consumption is low

across the full range of power supply voltages.

Like the NE556, the TLC556 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 pin (CONT). When the trigger input (TRIG) is

less than the trigger level, the flip-flop is set and the output goes high. If TRIG

is greater than the trigger level and the threshold input (THRES) is greater than

the threshold level, the flip-flop is reset and the output is low. The reset input

(RESET) overrides all other inputs and is used to initiate a new timing cycle. If

RESET is low, the flip-flop is reset and the output is low. Whenever the output is

low, a low-impedance path is provided between the discharge pin (DISCH) and the

ground pin (GND). Tie all unused inputs to an appropriate logic level to prevent

false triggering.

Although the CMOS output is capable of

sinking over 100mA and sourcing over 10mA, the TLC556 exhibits greatly reduced

supply-current spikes during output transitions. This feature minimizes the need for

the large decoupling capacitors required by the NE556.

The TLC556C is characterized for

operation from 0°C to 70°C. The TLC556I is characterized for operation from −40°C to

+85°C. The TLC556M is characterized for operation over the full military temperature

range of −55°C to +125°C.