Texas Instruments SN74LV138ATPWR

Overview

SN74LV138ATPWR from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in TSSOP-16 package, operating from 4.5 V to 5.5 V, with max propagation delay of 7.6 ns at 5 V, TTL-voltage-compatible inputs, and Ioff partial-power-down support. It enables high-speed memory decoding and data routing in industrial control and embedded logic systems.

For engineers reviewing the SN74LV138ATPWR datasheet, SN74LV138ATPWR pinout, SN74LV138ATPWR application, or SN74LV138ATPWR equivalent, key selection factors include enable-input logic (G1 active-high, G2A/G2B active-low), output drive capability (±12 mA), latch-up immunity (>250 mA), mixed-mode voltage operation, and thermal performance (θJA = 108°C/W).

Technical Context

The SN74LV138ATPWR implements positive-logic 3-to-8 decoding with three binary select inputs (A, B, C) and three enable inputs (G1, G2A, G2B), where only one of eight active-low outputs (Y0–Y7) is asserted per valid input combination. Its architecture supports cascading for larger decoders without external inverters - e.g., a 24-line decoder requires no additional gates.

Designed for partial-power-down operation, the device features Ioff circuitry that disables outputs when VCC = 0 V, preventing backflow current. It meets JESD 17 latch-up spec (>250 mA), JESD 22 ESD ratings (2000-V HBM, 200-V MM, 1000-V CDM), and supports mixed-mode voltage operation across all ports.

Key Specifications

Pinout & Package

TSSOP-16 (PW) package: 4.4 mm × 5.0 mm body, 1.2 mm max height, 0.65 mm pitch, exposed pad not present, RoHS-compliant NIPDAU finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-to-8 decoder applications.

Compared with SN74LV138ATPWR, SN74HC138N trades speed and robustness for cost and voltage flexibility, while 74LVC138APW offers superior speed at 3.3 V but mandates voltage translation in mixed-supply systems - SN74LV138ATPWR uniquely balances 5-V compatibility, 7.6-ns performance, and industrial-grade reliability.

Availability

SN74LV138ATPWR is available at Aetrix Electronics and suitable for industrial PLCs, automotive body controllers, medical diagnostics interfaces, and aerospace data concentrators requiring stable component supply across extended temperature and long production lifecycles.

Supply support for SN74LV138ATPWR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a U.S.-based semiconductor company founded in 1930, delivering analog, embedded processing, and connectivity solutions with emphasis on reliability, longevity, and technical documentation.

The SN74LV138ATPWR belongs to TI's LV logic family, engineered for high-speed 5-V digital systems requiring low power, strong noise immunity, and robust operation in harsh environments - especially memory and I/O expansion.

FAQ

What is the maximum clock or signal frequency supported by SN74LV138ATPWR?

SN74LV138ATPWR is a combinational logic device without an internal clock; its usable frequency depends on propagation delay and system timing margins. With max tpd = 7.6 ns at 5 V, it supports reliable operation in address/data paths up to ~100 MHz (10 ns period), assuming proper setup/hold timing from driving sources and load capacitance ≤15 pF. The SN74LV138ATPWR does not impose a fundamental frequency limit but constrains maximum toggle rate based on board-level signal integrity.

Does SN74LV138ATPWR support mixed-voltage operation between input and output sides?

Yes, SN74LV138ATPWR supports mixed-mode voltage operation on all ports: inputs tolerate TTL levels (0.8 V/2.0 V) across 4.5–5.5 V VCC, and outputs swing rail-to-rail (0 V to VCC) while driving loads referenced to the same VCC. This allows interfacing with 3.3-V controllers via series resistors or level translators, though direct 3.3-V input driving is not guaranteed without checking VIH/VIL at reduced VCC - the SN74LV138ATPWR is specified strictly for 4.5–5.5 V operation.

Can SN74LV138ATPWR be used as a demultiplexer, and how is data routed?

Yes, SN74LV138ATPWR functions as an 1-to-8 demultiplexer when one enable input (e.g., G1) serves as the data input and A/B/C act as select lines. With G2A and G2B held low, asserting G1 high routes the logic state to the selected Yx output (active-low). For example, G1 = HIGH + A=B=C=0 selects Y0 = LOW, effectively passing inverted data. The SN74LV138ATPWR thus provides true 1:8 demux capability with built-in inversion - no external gates needed.

What is the purpose of the Ioff specification for SN74LV138ATPWR, and when does it matter?

The Ioff specification ensures that when VCC = 0 V, all outputs enter a high-impedance state and leakage current remains below 5 µA - preventing backflow current from live inputs or outputs into the unpowered device. This is critical during hot-swap events, partial system power-down, or board-level power sequencing. In such cases, the SN74LV138ATPWR avoids disrupting other powered circuitry, making it suitable for modular industrial backplanes and redundant power architectures.

How does SN74LV138ATPWR handle unused inputs, and what happens if they float?

All unused inputs of SN74LV138ATPWR must be tied to VCC or GND; floating inputs cause increased ICC, erratic output behavior, and potential oscillation due to CMOS input stage metastability. TI explicitly warns that improper termination violates recommended operating conditions. For example, leaving G2A unconnected may result in spurious Yx activation. The SN74LV138ATPWR datasheet mandates hard-wiring unused enables or select lines - pull-up resistors to VCC (for G2A/G2B) or pull-downs (for G1) are acceptable, but floating is never permitted.