The **U74AHC245G-R20-R** is an 8-bit bidirectional bus transceiver typically manufactured by companies like UTC (Unisonic Technologies). It is designed for asynchronous two-way communication between data buses. --- ### 1. Technical Specifications Below are the primary electrical and operational characteristics of the device: | Feature | Specification | | :--- | :--- | | **Logic Type** | Octal Bus Transceiver (3-State) | | **Supply Voltage (Vcc)** | 2.0V to 5.5V | | **Input Type** | CMOS / TTL Compatible | | **Output Current** | ±8 mA (at 5V) | | **Propagation Delay** | ~5.8 ns (at 5V) | | **Operating Temperature** | -40°C to +125°C | | **Package Type** | TSSOP-20 (indicated by the 'G' and 'R20' suffix) | --- ### 2. Functional Description The device contains eight non-inverting buffers with 3-state outputs. It is controlled by two specific pins: * **Direction Control (DIR):** Determines the direction of data flow. * **High (H):** Data flows from Terminal A to Terminal B. * **Low (L):** Data flows from Terminal B to Terminal A. * **Output Enable ($\overline{OE}$):** Controls the output state. * **Low (L):** The device is active and transfers data. * **High (H):** The device is in a high-impedance state (isolation mode), effectively disconnecting the buses. ### 3. Pin Configuration The device usually follows the standard 20-pin layout: | Pin Number | Name | Description | | :--- | :--- | :--- | | 1 | DIR | Direction Control Input | | 2 - 9 | A1 - A8 | Data Inputs/Outputs (Port A) | | 10 | GND | Ground | | 11 - 18 | B8 - B1 | Data Inputs/Outputs (Port B) | | 19 | $\overline{OE}$ | Output Enable (Active Low) | | 20 | Vcc | Positive Supply Voltage | --- ### 4. Key Applications * **Bus Buffering:** Strengthening signals for long PCB traces or driving multiple loads. * **Voltage Level Shifting:** Since it is "AHC" (Advanced High-Speed CMOS), it can often interface between different logic levels (e.g., 5V to 3.3V) depending on Vcc configuration. * **Isolation:** Using the $\overline{OE}$ pin to isolate sections of a circuit during power-up or sleep modes. ### 5. Part Number Breakdown * **U74:** Unisonic Technologies Logic Series. * **AHC:** Advanced High-Speed CMOS technology. * **245:** Function code for Octal Bus Transceiver. * **G:** Halogen-free and RoHS compliant. * **R20:** TSSOP-20 Package. * **R:** Tape and Reel packaging.