SN74HCS138BQBR

Overview

The SN74HCS138BQBR is a high-speed silicon gate CMOS decoder manufactured by Texas Instruments. It functions as a three-to-eight line decoder/demultiplexer with Schmitt-trigger inputs, packaged in a WQFN-16 (BQB) format measuring 3.50 mm x 2.50 mm. The device operates within a supply voltage range of 2 V to 6 V and supports an ambient temperature range from -40°C to +125°C. Electrical characteristics include a typical supply current of 100 nA and output drive capabilities of ±7.8 mA at 6 V. Propagation delays vary between 7 ns and 53 ns depending on the voltage and temperature conditions.

Feature Summary

• Schmitt-trigger inputs provide tolerance for slow or noisy input signals
• Balanced CMOS push-pull outputs allow for similar sourcing and sinking currents
• Three strobe inputs simplify cascading and facilitate demultiplexing operations

Applications

• Memory device selection with shared data bus
• Reducing required number of outputs for chip select applications
• Routing data

Procurement Notes

Verify the specific BQB package designation matches the required footprint dimensions of 3.50 mm by 2.50 mm. Confirm that the thermal pad connection requirements align with the system ground strategy. Ensure the operating environment stays within the specified -40°C to +125°C range to maintain electrical performance specifications.

Selection Notes

Select this component when noise immunity is critical due to the inclusion of Schmitt-trigger inputs. The wide 2 V to 6 V supply range offers flexibility for various logic families. Consider the WQFN-16 package for space-constrained designs requiring efficient thermal dissipation through the exposed pad.

Part Context

This part belongs to the SN74HCS138 series, which utilizes high-speed CMOS technology. The HCS designation indicates the presence of Schmitt-trigger inputs, distinguishing it from standard HC or HCT variants. The BQB suffix specifically identifies the WQFN-16 package configuration offered by Texas Instruments.

Replacement Considerations

SN74HCS138PW

FAQ

How do the Schmitt-trigger inputs benefit signal integrity?

They provide hysteresis, making the device tolerant to slow input transitions and reducing susceptibility to noise.

What is the function of the G0, G1, and G2 pins?

These are strobe inputs used to enable or disable the outputs, simplifying cascading and demultiplexing functions.