XR-556

XR-556 Dual Timer GENERAL DESCRIPTION The XR-556 dual timing circuit contains two independent 555-type timers on a single monolithic chip. It is a direct, pin-for-pin replacement for the SEINE 556 dual timer. Each timer section is a highly stable controller capable of producing accurate time delays or oscillations. Independent output and control terminals are provided for each section as shown in the functional block diagram. In the monostable mode of operation, the time delay for each section is precisely controlled by one external resistor and one capacitor. For astable operation as an oscillator, the free-running frequency and the duty cycle of each section are accurately controlled with two external resistors and one capacitor. The XR-556 may be triggered or reset on falling waveforms. Each output can source or sink up to 150 mA or drive TIL circuits. The matching and temperature tracking characteristics between each timer section of the XR-556 are superior to those available from...