SL74HC221

SL74HC221 Dual Monostable Multivibrator The SL74HC221 is identical in pinout to the LS/ALS221. The device inputs are compatible with standard CMOS outputs; with pullup resistors, they are compatible with LS/ALSTTL outputs. There are two trigger inputs, A INPUT (negative edge) and B INPUT (positive edge). These inputs are valid for rising/falling signals The device may also be triggered by using the CLR input (positiveedge) because of the Schmitt-trigger input; after triggering the output maintains the MONOSTABLE state for the time period determined by the external resistor RX and capacitor CX. Taking CLR low breaks this MONOSTABLE STATE. If the next trigger pulse occurs during the MONOSTABLE period it makes the MONOSTABLE period longer. Outputs Directly Interface to CMOS, NMOS, and TTL Operating Voltage Range: 3.0 to 6.0 V Low Input Current: 1.0 µA High Noise Immunity Characteristic of CMOS Devices ORDERING INFORMATION SL74HC221N Plastic SL74HC221D SOIC TA = -55° to 125° C for all packages PIN ASSIGNMENT LOGIC DIAGRAM PIN 16 =VCC PIN 8 = GND FUNCTION TABLE Inputs Outputs CLR H H H H H X L L H L* L * Note Note (1) CX, RX, DX are external components. (2) DX is a clamping diode. The external capacitor is charged to VCC in the stand-by state, i.e. no trigger. When the supply voltage is turned off CX is discharged mainly through an internal parasitic diode. If CX is sufficiently large and VCC decreases rapidy, there will be some possibility of damaging the I.C. wit...