特性 Features

? Overriding Reset Terminates Output Pulse

? Triggering From the Leading or Trailing Edge

? Q and Q Buffered Outputs

? Separate Resets

? Wide Range of Output-Pulse Widths

? Schmitt Trigger on Both A and B Inputs

? Fanout (Over Temperature Range)

- Standard Outputs . . . . . . . . . . . . . . . 10 LSTTL Loads

- Bus Driver Outputs . . . . . . . . . . . . . 15 LSTTL Loads

? Wide Operating Temperature Range . . . -55oC to 125oC

? Balanced Propagation Delay and Transition Times

? Significant Power Reduction Compared to LSTTL

Logic ICs

? HC Types

- 2V to 6V Operation

- High Noise Immunity: NIL = 30%, NIH = 30%of VCC at

VCC = 5V

? HCT Types

- 4.5V to 5.5V Operation

- Direct LSTTL Input Logic Compatibility,

VIL= 0.8V (Max), VIH = 2V (Min)

- CMOS Input Compatibility, Il ≤ 1μA at VOL, VOH

描述 Description

The ’HC123, ’HCT123, CD74HC423 and CD74HCT423 are

dual monostable multivibrators with resets. They are all

retriggerable and differ only in that the 123 types can be

triggered by a negative to positive reset pulse; whereas the

423 types do not have this feature. An external resistor (RX)

and an external capacitor (CX) control the timing and the

accuracy for the circuit. Adjustment of Rx and CX provides a

wide range of output pulse widths from the Q and Q

terminals. Pulse triggering on the A and B inputs occur at a

particular voltage level and is not related to the rise and fall

times of the trigger pulses.

Once triggered, the output pulse width may be extended by

retriggering inputs A and B. The output pulse can be

terminated by a LOW level on the Reset (R) pin. Trailing

edge triggering (A) and leading edge triggering (B) inputs

are provided for triggering from either edge of the input

pulse. If either Mono is not used each input on the unused

device (A, B, and R) must be terminated high or low.

The minimum value of external resistance, Rx is typically

5kΩ. The minimum value external capacitance, CX, is 0pF.

The calculation for the pulse width is tW = 0.45 RXCX at

VCC = 5V.