The **AM26LS31** and **AM26LS32** series are foundational integrated circuits used for digital data transmission. They are designed to meet the requirements of ANSI Standards **TIA/EIA-422-B** (RS-422) and ITU Recommendation V.11. --- ## 1. Overview of the AM26LS3X Family This family consists of high-speed differential line drivers and receivers. They are primarily used to transmit data over long distances in noisy environments. | Part Number | Function | Description | | :--- | :--- | :--- | | **AM26LS31** | Quad Differential Line Driver | Converts single-ended TTL/LS inputs into differential RS-422 outputs. | | **AM26LS32** | Quad Differential Line Receiver | Converts differential RS-422 input signals back into single-ended TTL/LS outputs. | --- ## 2. Technical Specifications ### AM26LS31 (The Driver) * **Channels:** 4 independent driver channels. * **Output Type:** Complementary (Differential) outputs. * **Output Drive:** High current capability for driving twisted-pair lines. * **Propagation Delay:** Typically 10ns to 15ns. * **Power Supply:** Single 5V supply. ### AM26LS32 (The Receiver) * **Sensitivity:** Detects signals as small as ±200mV over a common-mode range of ±7V. * **Hysteresis:** Built-in input hysteresis (typically 50mV) for improved noise immunity. * **Input Impedance:** High input impedance (approx. 12kΩ). * **Fail-safe:** Inputs are designed to stay in a high state if the bus is open. --- ## 3. Key Features and Advantages ### Differential Signaling By using two wires per signal (A and B), these parts utilize **Common-Mode Rejection**. Any noise picked up by the cable affects both wires equally and is subtracted out by the receiver. ### Low Power Schottky (LS) The "LS" in the part name indicates **Low-power Schottky** technology, which provides a balance between high-speed switching and moderate power consumption. ### Enable/Disable Functions Both chips feature "Output Enable" (G) and "Complementary Output Enable" ($\bar{G}$) pins. This allows the outputs to be placed in a high-impedance state (Tri-state), which is essential for multi-point bus systems. --- ## 4. Typical Application Circuit In a standard RS-422 communication link, the AM26LS31 and AM26LS32 work together as shown below: ```text [ TTL Signal ] --> [ AM26LS31 Driver ] --- (Twisted Pair) --- [ AM26LS32 Receiver ] --> [ TTL Signal ] ``` ### Typical Wiring Table | Driver Pin (31) | Signal Name | Receiver Pin (32) | | :--- | :--- | :--- | | Y (Output +) | Differential Line A | A (Input +) | | Z (Output -) | Differential Line B | B (Input -) | | GND | Signal Ground | GND | --- ## 5. Summary of Use Cases * **Industrial Automation:** Communicating between PLCs and motor drives. * **Encoder Interfaces:** Reading high-speed pulses from rotary encoders over long cables. * **Serial Data Links:** Extending RS-422/RS-485 communication distances up to 1200 meters.