Texas Instruments SN74LV138ATPW

Overview

SN74LV138ATPW 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-compatible inputs, and Ioff partial-power-down support. It enables high-speed memory decoding and data routing in industrial control logic and address demultiplexing circuits.

For engineers reviewing the SN74LV138ATPW datasheet, SN74LV138ATPW pinout, SN74LV138ATPW application, or SN74LV138ATPW equivalent, key selection criteria include enable-input logic (G1 active-high, G2A/G2B active-low), output drive capability (±12 mA), thermal resistance (θJA = 108 °C/W), and compatibility with mixed-mode voltage systems.

Technical Context

The SN74LV138ATPW implements positive-logic 3-to-8 decoding using 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.

It features Ioff circuitry that disables outputs during power-down to prevent backflow current, and supports TTL-level input thresholds (VIL = 0.8 V, VIH = 2 V) while operating on a 5-V supply. All inputs must be tied to VCC or GND to avoid floating states.

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 SN74HC138N and SN74LVC138APWR, the SN74LV138ATPW uniquely balances 5-V compatibility, industrial temperature rating, Ioff safety, and TSSOP packaging - making it optimal for retrofitting legacy 5-V systems requiring reliability under thermal stress.

Availability

SN74LV138ATPW is available at Aetrix Electronics and suitable for industrial control logic, memory address decoding, and peripheral selection applications requiring stable component supply and long-term lifecycle support.

Supply support for SN74LV138ATPW 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 global semiconductor leader specializing in analog, embedded processing, and logic solutions, with over 90 years of innovation in industrial, automotive, and communications markets.

The SN74LV138ATPW belongs to TI's LV logic family, designed specifically for high-speed, low-power 5-V digital systems requiring robust noise immunity, mixed-voltage interoperability, and industrial-grade reliability.

FAQ

What is the maximum operating frequency supported by the SN74LV138ATPW?

The SN74LV138ATPW does not specify a clock frequency since it is a combinational logic device without internal clocking. Its usable speed is determined by propagation delay: max 7.6 ns at 5 V, enabling reliable operation in address decode paths up to ~100 MHz with appropriate setup/hold margins. System-level timing depends on connected loads and PCB routing.

Does the SN74LV138ATPW support 3.3-V input signals while powered at 5 V?

Yes, the SN74LV138ATPW supports mixed-mode voltage operation: inputs tolerate 0–5.5 V regardless of VCC, so 3.3-V logic signals may drive A, B, C, G1, G2A, or G2B directly without level shifting. This is confirmed in the "Mixed-Mode Voltage Operation" feature and Absolute Maximum Ratings table.

Is the SN74LV138ATPW pin-compatible with the SN74HC138?

No, the SN74LV138ATPW is not pin-compatible with the SN74HC138. While both are 16-pin decoders, the SN74HC138 uses SOIC-16 (D package) with different thermal pad and footprint dimensions. The SN74LV138ATPW uses TSSOP-16 (PW package), which has narrower body width (4.4 mm vs 7.5 mm), finer pitch (0.65 mm vs 1.27 mm), and distinct land pattern requirements.

What is the purpose of the Ioff feature in the SN74LV138ATPW?

The Ioff feature in the SN74LV138ATPW disables all outputs when VCC = 0 V, preventing damaging current backflow from live inputs into the unpowered device. This protects the IC during partial power-down sequences in multi-rail systems and ensures safe hot-insertion in modular electronics - a requirement explicitly verified in the datasheet's Ioff specification (≤5 µA).

Can the SN74LV138ATPW be used to demultiplex a single data line to eight outputs?

Yes, the SN74LV138ATPW can function as a 1-to-8 demultiplexer: tie the data signal to G1 (active-high enable), and use A, B, C as select lines; G2A and G2B must be held low. Each Yx output then mirrors the G1 input state (inverted due to active-low output), enabling data routing - a capability explicitly described in the datasheet's functional description and application section.