The **LS393D** (specifically the SN74LS393D) is a high-speed CMOS/TTL compatible integrated circuit that contains **two independent 4-bit binary counters**. It is widely used in digital electronics for frequency division, timing, and counting applications. --- ## 1. Key Specifications The "LS" in the name stands for **Low-power Schottky**, indicating a balance between high speed and low power consumption. The "D" suffix typically refers to the **SOIC (Small Outline Integrated Circuit)** surface-mount package. | Feature | Specification | | :--- | :--- | | **Logic Family** | LS-TTL | | **Function** | Dual 4-Bit Binary Counter | | **Supply Voltage (Vcc)** | 4.75V to 5.25V | | **Operating Temperature** | 0°C to 70°C | | **Count Frequency** | Up to 35 MHz (Typical) | | **Package Type** | SOIC-14 (14 pins) | --- ## 2. Pin Configuration The chip features two identical, independent counter sections. | Pin Number | Symbol | Description | | :--- | :--- | :--- | | 1 | 1CP | Clock Input (Counter 1) - Triggered on High-to-Low transition | | 2 | 1CLR | Clear Input (Counter 1) - Active High | | 3, 4, 5, 6 | 1Q0 - 1Q3 | Parallel Outputs (Counter 1) | | 7 | GND | Ground (0V) | | 8, 9, 10, 11| 2Q3 - 2Q0 | Parallel Outputs (Counter 2) | | 12 | 2CLR | Clear Input (Counter 2) - Active High | | 13 | 2CP | Clock Input (Counter 2) - Triggered on High-to-Low transition | | 14 | Vcc | Supply Voltage (+5V) | --- ## 3. Internal Logic & Functional Behavior The LS393D consists of eight master-slave flip-flops organized into two sets of four. ### Binary Counting Each 4-bit counter increments its value on the **negative edge** (falling edge) of the clock pulse. * **Modulo-16:** Each section counts from `0000` to `1111` (0 to 15 in decimal). * **Cascading:** By connecting the last output of the first counter ($1Q_3$) to the clock input of the second counter ($2CP$), you can create an **8-bit binary counter** (counting up to 255). ### Reset Function The `CLR` (Clear) pins are asynchronous. When a logic **HIGH** is applied to the Clear pin, all four bits of that counter are immediately reset to `0000`, regardless of the clock state. --- ## 4. Typical Applications 1. **Frequency Dividers:** Dividing a clock signal by 2, 4, 8, or 16. 2. **Digital Clocks:** Used in timing circuits to count seconds or minutes. 3. **Address Generators:** For cycling through memory addresses in simple hardware. 4. **Pulse Counting:** Counting external events in industrial sensors. ---