The **FST3244WM** is a high-speed CMOS 8-bit bus switch designed for low-power, high-performance applications. It belongs to the Fairchild/onsemi family of digital logic components. ### 1. Key Specifications The following table summarizes the primary electrical characteristics of the FST3244WM: | Parameter | Specification | | :--- | :--- | | **Switch Configuration** | 8-Bit (Octal) | | **Logic Family** | FST (Bus Switch) | | **Supply Voltage (Vcc)** | 4.0V to 5.5V | | **On-Resistance (R_on)** | 4Ω (Typical) | | **Propagation Delay** | 0.25ns (Max) | | **Package Type** | SOIC-20 (Wide) | | **Operating Temperature** | -40°C to +85°C | --- ### 2. Functional Description The FST3244WM acts like a series of mechanical switches but operates at electronic speeds. It is organized as two sets of 4-bit switches with separate **Output Enable (/OE)** controls. * **Internal Architecture:** It consists of N-channel FETs. When the enable pin is **Low**, the switch is "ON," connecting port A to port B. When the enable pin is **High**, the switch is "OFF," creating a high-impedance (Hi-Z) state. * **Near-Zero Delay:** Because it is a simple FET switch, it does not have the propagation delays associated with standard logic gates (buffers/inverters). The only delay is the RC time constant of the on-resistance and the load capacitance. * **Voltage Translation:** It can be used for 5V to 3.3V translation if a diode is placed in series with Vcc, effectively dropping the gate voltage and limiting the output voltage. --- ### 3. Pin Configuration (SOIC-20) Below is a simplified representation of the pinout for the 20-pin wide SOIC package: | Pin Number | Name | Function | | :--- | :--- | :--- | | 1 | /OE1 | Output Enable 1 (Active Low) | | 2 - 9 | A1 - A8 | Port A Data I/O | | 10 | GND | Ground | | 11 - 18 | B8 - B1 | Port B Data I/O | | 19 | /OE2 | Output Enable 2 (Active Low) | | 20 | Vcc | Power Supply | --- ### 4. Typical Applications * **Bus Isolation:** Isolating a heavily loaded bus from a processor to improve signal integrity. * **Hot-Plugging:** Protecting sensitive components when peripherals are plugged in while the system is powered. * **Signal Gating:** Routing signals between multiple memory modules or peripherals. * **Voltage Level Shifting:** Bridging legacy 5V systems with newer 3.3V logic.