M74HCT138B1R

Overview

The M74HCT138B1R is a high-speed CMOS 3-to-8 line decoder fabricated with silicon gate C2MOS technology. It features three binary select inputs (A, B, and C) that determine which of the eight outputs goes low when enabled. The device includes three enable inputs to facilitate cascade connections and address decoding for memory systems. All inputs are equipped with protection circuits against static discharge and transient excess voltage.

Feature Summary

• High-speed operation with typical propagation delay of 16ns at VCC = 4.5V
• Low power dissipation with maximum quiescent current of 4μA at TA=25°C
• Compatible with TTL outputs, featuring VIH = 2V (MIN.) and VIL = 0.8V (MAX)
• Symmetrical output impedance with |IOH| = IOL = 4mA (MIN)

Applications

• Address decoders for memory systems
• Cascade connection applications
• General-purpose digital logic decoding

Procurement Notes

Verify component authenticity through authorized STMicroelectronics distributors or certified suppliers. Confirm datasheet revision matches the specific manufacturing lot. Check RoHS compliance status as required by regional regulations. Ensure storage conditions adhere to specified limits to prevent moisture damage prior to soldering.

Selection Notes

Select this component for designs requiring 3-to-8 decoding with TTL-compatible input levels. Suitable for applications needing symmetrical output drive capabilities. Consider package availability; DIP-16 is standard for through-hole mounting. Verify operating temperature range requirements against -55°C to 125°C specification.

Part Context

Part of the M74HCT138 series from STMicroelectronics. Belongs to the 74HCT logic family, designed for compatibility with TTL circuits while offering CMOS advantages. Functionally pin-compatible with standard 74LS138 devices.

Replacement Considerations

Direct substitutes include CD74HC138E (Texas Instruments), SN74HC138N (Texas Instruments), and TC74HC138APF (Toshiba). Verify voltage level compatibility as these may be HC rather than HCT variants.