74195
74195 4-Bit Parallel-Access Shift Register
Overview
The 74195 is a high-speed 4-bit parallel-access shift register designed for a wide range of digital applications. It combines the functionality of a shift register with parallel input/output capabilities, making it highly versatile for data storage, transfer, and manipulation tasks. The device operates on TTL (Transistor-Transistor Logic) voltage levels and is compatible with most standard logic families.
The 74195 features both serial and parallel data inputs, allowing flexible data loading options. It supports synchronous parallel loading, serial shifting, and hold modes, controlled by dedicated input pins. The register is edge-triggered, ensuring reliable operation at high clock speeds.
Key Features
- 4-bit parallel input/output shift register with serial capability
- High-speed operation with typical propagation delay of 15ns
- Synchronous parallel loading
- Serial data input for shift-right operations
- Asynchronous master reset (clear) function
- Two control inputs for mode selection (shift/load)
- Direct overriding clear input
- TTL-compatible inputs and outputs
- Wide operating voltage range: 4.75V to 5.25V
- Low power consumption: typically 45mW
- Available in multiple package options
Applications
The 74195 is suitable for various digital system applications, including:
- Serial-to-parallel data conversion
- Parallel-to-serial data conversion
- Temporary data storage/buffering
- Sequence generators
- Time delay circuits
- Data pattern recognition systems
- Digital communications interfaces
- Arithmetic processing units
- Peripheral interface circuits
- Test and measurement equipment
Functional Description
The 74195 operates in three primary modes, controlled by the J, K, and SH/LD inputs:
- Parallel Load Mode: When SH/LD is low, data present at the parallel inputs (P0-P3) is loaded into the register on the rising edge of the clock.
- Shift Mode: When SH/LD is high, data shifts right on each rising clock edge. The serial input is determined by the J and K inputs, which function similarly to a J-K flip-flop.
- Hold Mode: When the clock is held low, the register maintains its current state regardless of input changes.
The asynchronous master reset (MR) input, when activated (low), clears all flip-flops immediately, independent of the clock state.
Electrical Characteristics
Absolute Maximum Ratings
| Parameter | Value | Unit |
|---|---|---|
| Supply Voltage (Vcc) | 7 | V |
| Input Voltage | 5.5 | V |
| Operating Temperature Range | 0 to +70 | °C |
| Storage Temperature Range | -65 to +150 | °C |
Recommended Operating Conditions
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Supply Voltage (Vcc) | 4.75 | 5.0 | 5.25 | V |
| High-Level Input Voltage | 2.0 | - | - | V |
| Low-Level Input Voltage | - | - | 0.8 | V |
| Clock Frequency | - | - | 35 | MHz |
Switching Characteristics (Vcc = 5V, TA = 25°C)
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Propagation Delay (Clock to Q) | - | 15 | 27 | ns |
| Setup Time (Parallel Inputs) | 20 | - | - | ns |
| Hold Time (Parallel Inputs) | 5 | - | - | ns |
| Clock Pulse Width (High) | 12 | - | - | ns |
| Clock Pulse Width (Low) | 12 | - | - | ns |
Package Information
The 74195 is available in several package options:
- PDIP-16 (Plastic Dual In-line Package): 19.3mm × 6.35mm body, 2.54mm pin spacing
- SOIC-16 (Small Outline Integrated Circuit): 9.9mm × 3.9mm body, 1.27mm pin spacing
- CDIP-16 (Ceramic Dual In-line Package): Hermetically sealed ceramic package for military applications
