## Overview of the FST3345MTC The **FST3345MTC** is a high-speed CMOS 8-bit bus switch manufactured by Fairchild Semiconductor (now part of ON Semiconductor). It is designed to facilitate high-speed switching and signal isolation between components on a circuit board without introducing significant propagation delay. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Logic Type** | 8-bit Bus Switch | | **Technology** | CMOS | | **Supply Voltage ($V_{CC}$)** | 4.0V to 5.5V | | **Propagation Delay** | < 0.25 ns (Negligible) | | **ON-State Resistance ($R_{on}$)** | ~4 $\Omega$ (Typical) | | **Package Type** | TSSOP-20 (MTC Suffix) | | **Operating Temperature** | -40°C to +85°C | --- ### 2. Pin Configuration and Functions The FST3345 features an 8-bit path controlled by an Output Enable ($\overline{OE}$) pin. | Pin Name | Description | | :--- | :--- | | **$A_0 - A_7$** | Port A inputs/outputs (Bi-directional) | | **$B_0 - B_7$** | Port B inputs/outputs (Bi-directional) | | **$\overline{OE}$** | Output Enable (Active LOW) | | **$V_{CC}$** | Positive Power Supply | | **GND** | Ground | --- ### 3. Functional Description The FST3345 operates as a literal electronic switch. When the control signal is active, it creates a low-resistance path between the A and B ports. * **Switch ON:** When $\overline{OE}$ is **LOW (0)**, the switch is closed. Port A is connected to Port B, allowing data to flow in either direction. * **Switch OFF:** When $\overline{OE}$ is **HIGH (1)**, the switch is open. Port A and Port B are isolated (High-Impedance state). #### Key Advantage: Near-Zero Delay Because the device does not "buffer" the signal using transistors that regenerate the logic level, but rather acts as a pass-gate, it introduces virtually no timing delay to the data stream. --- ### 4. Typical Applications * **Bus Isolation:** Isolating a loaded bus from the CPU to reduce capacitance and increase speed. * **Voltage Level Translation:** If $V_{CC}$ is set to 5V, the device can be used to interface 5V signals with lower voltage logic (depending on the specific input/output configuration). * **Hot-Plugging:** Protecting sensitive circuitry during the insertion of peripheral cards. * **Signal Multiplexing:** Directing data paths between different memory modules or peripherals. --- ### 5. Package Information: TSSOP-20 The **MTC** suffix indicates the **Thin Shrink Small Outline Package (TSSOP)** with 20 pins. This is a surface-mount package characterized by a very small footprint and low profile, making it ideal for space-constrained mobile or embedded designs.