HD74AC123A

HD74AC123A Dual Retriggerable Resettable Multivibrator Description Each half of the HD74AC123A features retriggerable capability, complementary dc level triggering and overriding Direct Clear. When a circuit is in the quasi-stable (delay) state, another trigger applied to the inputs (per the Truth Table) will cause the delay period to start again, without disturbing the outputs. By repeating this process, the output pulse period (Q High, Q Low) can be made as long as desired. Alternatively, a delay period can be terminated at any time by a Low signal on C D, which also inhibits triggering. An internal connection from C D to the input gate makes it possible to trigger the circuit by a positive-going signal on C D, as shown in the Truth Table. For timing capacitor values greater than 1000 pF, the output pulse width is defined as follows. Where tw is in ns, RX is in k and C tw = RXCX X is in pF. Feature Outputs Source/Sink 24 mA HD74AC123A Pin Arrangement A1 1 B1 2 CD1 3 Q1 4 Q2 5 CX2 6 RX2CX2 7 GND 8 (Top view) 16 VCC 15 RX1CX1 14 CX1 13 Q1 12 Q2 11 CD2 10 B2 9 A2 Logic Symbol 7 6 (15) (14) RXCX CX Q 9(1) A 10(2) B Q CD 12(4) 5(13) 11 (3) VCC = Pin16 GND = Pin8 2 HD74AC123A Pin Names A1, A 2 B 1, B 2 C D1, CD2 Q1, Q2 Q1, Q 2 Trigger Inputs (Active Falling Edge) Trigger Inputs (Active Rising Edge) Direct Clear Inputs (Active Low) Positive Pulse Outputs Negative Pulse Outputs Triggering Truth Table Inputs A X B X L H H L L H : L : X : : : H High Voltage Level Low Vol...