## Overview of the 74FST3384 The **74FST3384** is a high-speed CMOS 10-bit bus switch. It is designed to facilitate high-speed connection or isolation between two buses without adding significant propagation delay or generating additional ground bounce noise. ### Key Functional Specifications | Feature | Specification | | :--- | :--- | | **Logic Family** | FST (Fast Switch Technology) | | **Bit Width** | 10-Bit (Dual 5-bit sections) | | **Propagation Delay** | < 0.25 ns (Negligible) | | **Operating Voltage** | 4.0V to 5.5V | | **On-Resistance ($R_{on}$)** | 4 $\Omega$ (Typical) | | **Control Logic** | Active-Low Output Enable ($\overline{OE}$) | --- ### Pin Configuration and Architecture The device consists of two banks of five switches. Each bank is controlled by its own Output Enable ($\overline{OE}$) pin. | Pin Name | Description | | :--- | :--- | | **$1\overline{OE}, 2\overline{OE}$** | Control inputs (Active Low). When LOW, the switches are ON. | | **A0 - A9** | Data Input/Output Bus A. | | **B0 - B9** | Data Input/Output Bus B. | | **VCC** | Power Supply (Typically 5V). | | **GND** | Ground. | --- ### Internal Logic and Truth Table When the $\overline{OE}$ signal is driven low, the switch closes, allowing signals to pass bi-directionally between Port A and Port B. When $\overline{OE}$ is high, the switch is in a high-impedance (Hi-Z) state, effectively isolating the two buses. | $\overline{OE}$ Input | State of Bus (A, B) | | :---: | :--- | | **L** | A Port = B Port (Connected) | | **H** | Disconnected (High Impedance) | --- ### Critical Characteristics for Design 1. **Near-Zero Propagation Delay:** Because it is a simple FET switch rather than a buffer/driver, it does not have a clock cycle latency. The only delay is the $RC$ time constant of the on-resistance and the load capacitance. 2. **Bi-directional Data Flow:** Since there are no internal amplifiers, data can flow from A to B or B to A interchangeably. 3. **Low Power Consumption:** Being a CMOS device, it draws minimal static current ($I_{CC}$), making it ideal for power-sensitive applications. 4. **Voltage Translation:** It can be used for level shifting (e.g., 5V to 3.3V) if a diode is placed in series with the VCC or if specific VCC levels are maintained. --- ### Common Applications * **Hot-Plugging:** Protecting sensitive circuitry during live insertion of cards. * **Bus Isolation:** Separating a heavily loaded bus into smaller segments to reduce capacitive loading. * **Voltage Level Shifting:** Bridging different logic voltage families. * **Memory Interleaving:** Switching between different banks of SDRAM or Flash memory.