## Overview of SN74HCT393D The **SN74HCT393D** is a high-speed CMOS device featuring dual 4-bit binary counters. It is designed to be pin-compatible with standard TTL (Transistor-Transistor Logic) and is widely used for frequency division, timing, and digital counting applications. --- ### Technical Specifications | Parameter | Specification | | :--- | :--- | | **Logic Family** | HCT (High-Speed CMOS with TTL thresholds) | | **Function** | Dual 4-Bit Binary Counter | | **Supply Voltage ($V_{CC}$)** | 4.5V to 5.5V | | **Input Logic Levels** | TTL Compatible (Low $\leq$ 0.8V, High $\geq$ 2.0V) | | **Max Frequency ($f_{max}$)** | Typ. 27 MHz (at 4.5V) | | **Package Type** | SOIC-14 (Surface Mount) | | **Operating Temperature** | -40°C to +85°C (or up to 125°C) | --- ### Functional Breakdown The chip contains two independent 4-bit counters ($2^4 = 16$ states each). Each counter has the following features: 1. **Clock Input ($\overline{CP}$):** The counter increments on the **high-to-low transition** (falling edge) of the clock signal. 2. **Master Reset (MR):** An active-high signal. When MR is HIGH, all counter stages are cleared to LOW (0000), overriding the clock. 3. **Outputs ($Q_0$ to $Q_3$):** These provide the binary count. $Q_0$ is the Least Significant Bit (LSB), and $Q_3$ is the Most Significant Bit (MSB). ### Pin Configuration (SOIC-14) | Pin No. | Symbol | Description | | :--- | :--- | :--- | | 1, 13 | 1CP, 2CP | Clock Inputs (Negative-edge triggered) | | 2, 12 | 1MR, 2MR | Master Reset Inputs (Active High) | | 3-6 | 1Q0 - 1Q3 | Outputs for Counter 1 | | 7 | GND | Ground (0V) | | 8-11 | 2Q3 - 2Q0 | Outputs for Counter 2 | | 14 | $V_{CC}$ | Supply Voltage | --- ### Key Applications * **Frequency Dividers:** By connecting the output of one stage to the clock of another, you can divide frequencies by powers of 2 (2, 4, 8, 16, etc.). * **Time Delay Generation:** Used in circuits requiring specific pulse intervals. * **Digital Clocks:** Serving as the base for seconds, minutes, or hour counters. * **ASIC Glue Logic:** Interfacing between different voltage domains or logic families where TTL compatibility is required. --- ### Connection Example (Pseudo-code Logic) To create an 8-bit counter, you can cascade the two 4-bit counters: ```c // Cascading Logic: // 1. Input signal goes to 1CP (Pin 1). // 2. Connect 1Q3 (Pin 6) to 2CP (Pin 13). // 3. Ground both 1MR and 2MR to allow counting. // 4. Resulting 8-bit value is [2Q3...2Q0, 1Q3...1Q0]. ```