## SN74CBT16811CDGGR Technical Overview The **SN74CBT16811CDGGR** is a high-speed CMOS FET (Field-Effect Transistor) bus switch manufactured by Texas Instruments. It is designed to facilitate 24-bit bus switching or port exchange with minimal propagation delay. --- ### 1. General Specifications | Feature | Specification | | :--- | :--- | | **Manufacturer** | Texas Instruments | | **Logic Family** | CBT (Cross-Bar Technology) | | **Function** | 24-Bit FET Bus Switch | | **Package Type** | TSSOP-56 (Thin Shrink Small Outline Package) | | **Operating Voltage** | 4.0V to 5.5V | | **Propagation Delay** | 0.25 ns (Max) | | **Operating Temperature** | -40°C to +85°C | --- ### 2. Key Internal Components & Architecture The device consists of two banks of 12-bit switches that can be controlled independently. 1. **N-Channel FETs**: The heart of the chip. When the switch is ON, the FET provides a low-resistance path between ports. When OFF, the FET provides high impedance (isolation). 2. **Output Enable ($\overline{OE}$)**: Active-low control pins. * When $\overline{1OE}$ is low, the first 12 bits are connected. * When $\overline{2OE}$ is low, the second 12 bits are connected. 3. **Level Shifting Support**: While primarily a switch, it can be used for 5V to 3.3V translation if used in conjunction with a series resistor or specific biasing. --- ### 3. Pin Configuration Summary | Pin Group | Function | Description | | :--- | :--- | :--- | | **1A1 - 2A12** | Port A | Input/Output nodes for the A-bus. | | **1B1 - 2B12** | Port B | Input/Output nodes for the B-bus. | | **$\overline{1OE}, \overline{2OE}$** | Control | Enable/Disable switches for each 12-bit bank. | | **VCC / GND** | Power | Standard power supply and ground pins. | --- ### 4. Why use this part? * **Near-Zero Delay**: Because it uses a FET switch rather than a buffer/driver, it does not add significant timing delays to high-speed data lines. * **Low Power Consumption**: Since it is CMOS-based, it consumes very little static power (typical $I_{CC}$ is in $\mu A$ range). * **Bidirectional Operation**: Data can flow from A to B or B to A without a direction control pin. --- ### 5. Application Example (Code Concept) While this is a hardware switch, it is often controlled by a microcontroller (MCU) or FPGA. ```c // Example: Controlling the SN74CBT16811 via an MCU #define OE_BANK1 5 // Pin connected to 1OE #define OE_BANK2 6 // Pin connected to 2OE void setup() { pinMode(OE_BANK1, OUTPUT); pinMode(OE_BANK2, OUTPUT); // Disable both banks initially (High-Z) digitalWrite(OE_BANK1, HIGH); digitalWrite(OE_BANK2, HIGH); } void enable_bridge() { // Connect A-bus to B-bus digitalWrite(OE_BANK1, LOW); digitalWrite(OE_BANK2, LOW); } ```