7485
7485 - 4-Bit Magnitude Comparator
Overview
The 7485 is a high-speed 4-bit magnitude comparator designed for digital systems requiring comparison operations. This TTL (Transistor-Transistor Logic) component is capable of comparing two 4-bit binary numbers and determining their relationship (greater than, less than, or equal). It is widely used in arithmetic logic units (ALUs), control systems, and data processing applications where numerical comparison is essential.
The device features cascading inputs, allowing multiple 7485 ICs to be connected for comparing numbers larger than 4 bits. Its high-speed operation makes it suitable for applications requiring quick decision-making based on numerical comparisons.
Features
- High-Speed Operation: Typical propagation delay of 23ns for efficient performance in time-critical applications.
- 4-Bit Comparison: Compares two 4-bit words (A and B) with three possible outputs (A>B, A
- Cascading Capability: Expansion inputs allow connection of multiple comparators for comparing words longer than 4 bits.
- TTL-Compatible: Fully compatible with standard TTL logic families.
- Wide Operating Voltage: Operates with a supply voltage range of 4.75V to 5.25V.
- Low Power Consumption: Typical power dissipation of 75mW.
- Standard 16-Pin Package: Available in PDIP, CDIP, and SOIC packages for flexibility in system design.
Applications
The 7485 magnitude comparator finds use in various digital systems and applications, including:
- Arithmetic Logic Units (ALUs) in microprocessors
- Digital signal processing systems
- Control systems and decision-making circuits
- Data sorting and ranking systems
- Address decoding in memory systems
- Process control equipment
- Test and measurement instruments
- Educational demonstration circuits for digital logic
Electrical Characteristics
Absolute Maximum Ratings
- Supply Voltage (Vcc): 7V
- Input Voltage (Vin): 5.5V
- Operating Temperature Range: 0°C to +70°C (commercial grade)
- Storage Temperature Range: -65°C to +150°C
Recommended Operating Conditions
- Supply Voltage (Vcc): 4.75V to 5.25V
- High-Level Input Voltage (VIH): 2V min
- Low-Level Input Voltage (VIL): 0.8V max
- Operating Temperature: 0°C to +70°C
DC Characteristics
- High-Level Output Voltage (VOH): 2.4V min (IOL = -400μA)
- Low-Level Output Voltage (VOL): 0.4V max (IOH = 16mA)
- Input Clamp Voltage (VIK): -1.5V max (II = -18mA)
- Input Current (II): ±1μA max (VIN = 2.7V or 0.4V)
- Short-Circuit Output Current (IOS): -18mA to 55mA
- Supply Current (ICC): 15mA typical, 22mA max
AC Characteristics
- Propagation Delay (A,B to Output): 23ns typical, 35ns max
- Propagation Delay (Cascading Inputs to Output): 35ns typical, 50ns max
- Input Capacitance: 3pF typical
- Power Dissipation: 75mW typical, 110mW max
Functional Description
The 7485 compares two 4-bit binary numbers (A3A2A1A0 and B3B2B1B0) and provides three outputs indicating the relationship between them. The device also features three cascading inputs (A>B, A The comparison is performed from the most significant bit (MSB) to the least significant bit (LSB). If the MSBs are equal, the comparison moves to the next lower bit, and so on. The cascading inputs are used when comparing numbers longer than 4 bits - they represent the comparison result of higher-order bits. When implementing the 7485 in a circuit design, consider the following:Truth Table
Comparison Inputs
Cascading Inputs
Outputs
A3:B3, A2:B2, A1:B1, A0:B0
A>B, A A>B, A
A > B
X X X
1 0 0
A < B
X X X
0 1 0
A = B
1 0 0
1 0 0
A = B
0 1 0
0 1 0
A = B
0 0 1
0 0 1
Package Information
16-Pin DIP Package
Pin Configuration
Design Considerations
