74AC139SC

Overview

The Fairchild Semiconductor 74AC139SC is a dual 2-line-to-4-line decoder/demultiplexer integrated circuit belonging to the AC logic series. It features CMOS construction with TTL-compatible inputs and inverted outputs, housed in a 16-pin SOIC package. The device operates on a single supply voltage ranging from 2.0V to 6.0V and supports an operating temperature range of -40°C to 85°C. Each decoder section includes two address inputs and four active-low data outputs, controlled by independent enable inputs for flexible system integration.

Feature Summary

• Dual independent 2-to-4 line decoding functionality within a single package
• TTL-compatible input levels ensuring compatibility with standard logic families
• Active-low output states providing inverted signal decoding
• CMOS technology enabling low power consumption and high noise immunity

Applications

• Address decoding for memory and I/O port selection in embedded systems
• Demultiplexing data streams to multiple peripheral devices
• Control logic generation for sequential circuits and state machines
• Chip select signal generation in microprocessor-based architectures

Procurement Notes

Verify the manufacturer marking and date code against official Fairchild or onsemi documentation to confirm authenticity. Ensure the part number suffix matches the specified SOIC-16 package variant. Cross-reference electrical specifications with the current datasheet as product lines may transition between manufacturers. Confirm RoHS compliance status if required for specific regulatory environments.

Selection Notes

Select this component when dual independent decoding channels are required in a compact surface-mount footprint. The AC series offers faster switching speeds compared to legacy LS variants while maintaining lower power dissipation than HC types. Verify that the inverted output polarity aligns with downstream gate requirements. Ensure the supply voltage range accommodates the system's nominal rail voltage.

Part Context

This device is part of the widely adopted 74AC logic family, designed to bridge performance gaps between older bipolar technologies and newer CMOS standards. The 74AC139 specifically addresses applications requiring multiple decoding functions without consuming excessive board space. Its pinout compatibility with previous generations facilitates design upgrades in existing hardware platforms.

Replacement Considerations

Direct substitutes include the 74ACT139SC for higher speed operation with identical pinouts. Other compatible alternatives encompass the 74HC139 and 74HCT139, though input/output voltage thresholds differ. Verify package dimensions and thermal characteristics when swapping between AC, ACT, and HC series variants.