DESCRIPTION
The MC74AC353/74ACT353 contains two identical 4-input multiplexers with 3-state outputs. They select two bits from four sources selected by common Select inputs (S0, S1). The 4-input multiplexers have individual Output Enable (OEa, OEb) inputs which, when HIGH, force the outputs to a high impedance (High Z) state. The logic equations for the outputs are shown below: Za = OEa●(I0a●S1●S0+I1a●S1●S0+ I2a●S1●S0+I3a●S1●S0) Zb = OEb●(I0b●S1●S0+I1b●S1●S0+ I2b●S1●S0+I3b●S1●S0) If the outputs of 3-state devices are tied together, all but one device must be in the high impedance state to avoid high currents that would exceed the maximum ratings. Designers should ensure that Output Enable signals to 3-state devices whose outputs are tied together are designed so that there is no overlap. LOGIC DIAGRAM OEb I3b I2b I1b I0b S0 S1 I3a I2a I1a I0a OEa Zb Za Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
Motorola
