SCT1555

PRECISION SINGLE CELL TIMER ISSUE 2 - MAY 1998 DEVICE DESCRIPTION These devices are precision timing circuits for generation of accurate time delays or oscillation. Advanced circuit design means that these devices can operate from a single battery cell with the minimum of quiescent current. In monostable mode time delays are controlled by a single resistor and capacitor network. In astable mode the frequency and du t y cy c l e c a n be a c c u r a t e l y an d independently controlled with two external resistors and one capacitor. The threshold and trigger levels are normally set as a proportion of VCC by internal resistors. These levels can be programmed by the use of the control input pin. When the trigger input reduces to a value below the trigger level, the flip-flop is set and the output goes high. With the trigger input above the trigger level and the threshold input above the threshold level, the flip-flop is reset ZSCT1555 and the output goes low. The reset pin has priority over all the other inputs and is used to start new timing cycles. A low on the reset input causes the flip-flop to reset forcing the output low. Whenever the output is forced low then the internal discharge transistor is turned on. FEATURES 0.9V supply operating voltage guaranteed Pin connections comparable with 555 series timers Very low quiescent current 74 µA SO8 and DIL8 packages Operating temperature range compatible with battery technologies APPLICATIONS Portable and batte...