74LS688 8-bit Magnitude Comparator
Package PDIP, SOIC Series 74LS
74LS688 overview
The 74LS series of integrated circuits (ICs) was one of the most popular logic families of transistor-transistor logic (TTL) logic chips. 74LS series is a bipolar, low-power Schottky IC.74LS688 is an 8-bit magnitude comparator. 74LS688 is designed to perform comparisons between two eight-bit binary or BCD words. All device types provide P = Q outputs and the LS682 and LS684 have P>Q outputs also.
Key specifications
Supply Voltage
4.75 - 5.25Vdc
Maximum Clock Frequency
40Mhz
Power Dissipation
2mW/gate @100kHz
Minimum Output Current
8mA
Propagation Delay
10nS
Fan Out (TTL Loads)
20
Datasheet
688.pdf
74LS688 features
- Designed to Perform Comparisons Between Two 8-bit Binary or BCD Words
- Totem Pole Output
- Provides Equal Comparison Result
- Operating Temperature up to 70°C
- Standard TTL Switching Voltages
74LS688 pinout
| Pin | Name | Description |
|---|---|---|
| 1 | G' | Enable Input (Active Low) |
| 2 | P0 | Bit 0 of Comparator 1 |
| 3 | Q0 | Bit 0 of Comparator 2 |
| 4 | P1 | Bit 1 of Comparator 1 |
| 5 | Q1 | Bit 1 of Comparator 2 |
| 6 | P2 | Bit 2 of Comparator 1 |
| 7 | Q2 | Bit 2 of Comparator 2 |
| 8 | P3 | Bit 3 of Comparator 1 |
| 9 | Q3 | Bit 3 of Comparator 2 |
| 10 | GND | Ground |
| 11 | P4 | Bit 4 of Comparator 1 |
| 12 | Q4 | Bit 4 of Comparator 2 |
| 13 | P5 | Bit 5 of Comparator 1 |
| 14 | Q5 | Bit 5 of Comparator 2 |
| 15 | P6 | Bit 6 of Comparator 1 |
| 16 | Q6 | Bit 6 of Comparator 2 |
| 17 | P7 | Bit 7 of Comparator 1 |
| 18 | Q7 | Bit 7 of Comparator 2 |
| 19 | P'=Q' | Comparator Equal Output Pin |
| 20 | VCC | Positive Supply |
74LS688 applications
- Null detectors
- Zero-crossing detectors
- Relaxation oscillator
- Level shifter
- Analog-to-digital converters
- Window detectors
Application circuit
More about 74LS688
74LS688 Circuit
Below is a circuit of 1-bit magnitude comparator using logic gates (NOT, AND, and NOR).
74LS688 Alternative Equivalent
74LS682
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