Texas Instruments SN74LV138APWRE4

Overview

SN74LV138APWRE4 from Texas Instruments is a 3-line to 8-line decoder/demultiplexer IC operating from 2 V to 5.5 V, with 9.5 ns maximum propagation delay at 5 V, Ioff-enabled partial-power-down capability, and mixed-mode voltage operation across all ports. It selects one of eight active-low outputs using three binary address inputs (A0–A2) and three enable inputs (G2, G0, G1), commonly used in memory decoding and output expansion for microcontroller-based peripheral interfaces.

For engineers reviewing the SN74LV138APWRE4 datasheet, SN74LV138APWRE4 pinout, SN74LV138APWRE4 application, or SN74LV138APWRE4 equivalent, key selection criteria include its 16-pin TSSOP package, guaranteed 2.5–5.5 V switching performance, Ioff specification for system-level power sequencing, low ground bounce (<0.8 V at 3.3 V), and compatibility with 3.3 V/5 V mixed-voltage logic domains.

Technical Context

The SN74LV138APWRE4 implements a positive-logic 3-to-8 decoder with two active-low (G0, G1) and one active-high (G2) enable inputs, enabling hierarchical expansion without external inverters - e.g., a 24-line decoder requires no external logic, while a 32-line decoder needs only one inverter. Its standard CMOS inputs and balanced push-pull outputs support clean signal routing in high-density PCB layouts.

Functional mode control relies on simultaneous evaluation of A0–A2 address bits and all three enables; only when G2 = HIGH and both G0 = G1 = LOW does decoding activate, driving exactly one Y0–Y7 output LOW while others remain HIGH. The Ioff circuitry ensures <5 µA leakage per terminal during power-down, preventing backflow when VCC = 0 V.

Key Specifications

Pinout & Package

PW package: 16-pin Thin Shrink Small Outline Package (TSSOP), 5.00 mm × 4.40 mm body size, 0.65 mm lead pitch, exposed thermal pad (not electrically connected in PW variant).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC138N and 74LVC138AD, SN74LV138APWRE4 uniquely combines 2–5.5 V operation, 9.5 ns speed at 5 V, Ioff safety, and industry-standard 16-pin TSSOP packaging - making it optimal for modern mixed-voltage embedded systems requiring timing-critical, power-aware decoding.

Availability

SN74LV138APWRE4 is available at Aetrix Electronics and suitable for memory address decoding, LED matrix control, 7-segment display multiplexing, and peripheral enable distribution requiring stable component supply across industrial, automotive, and consumer electronics programs.

Supply support for SN74LV138APWRE4 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 delivering analog and embedded processing solutions, with over 90 years of innovation in logic, power management, and signal chain technologies.

The SN74LV138APWRE4 belongs to TI's LV family of low-voltage, high-speed CMOS logic devices engineered for robust operation across wide supply ranges and demanding industrial environments.

FAQ

What is the maximum propagation delay of the SN74LV138APWRE4 at 3.3 V?

The SN74LV138APWRE4 has a maximum propagation delay of 13.5 ns at VCC = 3.3 V with 15 pF load capacitance, measured from any address or enable input to any Y output. This value is specified across the full operating temperature range (–40°C to +85°C) and ensures reliable timing in 3.3 V systems running up to ~70 MHz address bus frequencies. The SN74LV138APWRE4 maintains consistent performance due to its CMOS process optimization for low-voltage operation.

Does the SN74LV138APWRE4 support partial-power-down mode?

Yes, the SN74LV138APWRE4 supports partial-power-down mode via its Ioff feature. When VCC = 0 V, all outputs are disabled and leakage current is limited to ≤5 µA per terminal, preventing damaging current backflow from live inputs or outputs into the unpowered device. This behavior is explicitly characterized in the Electrical Characteristics table and makes the SN74LV138APWRE4 suitable for hot-swap and multi-rail power architectures where subsystems power up/down independently.

Can the SN74LV138APWRE4 interface directly with 5 V logic inputs while operating at 3.3 V VCC?

Yes, the SN74LV138APWRE4 supports mixed-mode voltage operation: its inputs tolerate voltages from 0 V to 5.5 V regardless of VCC level. When VCC = 3.3 V, the SN74LV138APWRE4 correctly interprets 5 V TTL or CMOS signals as valid logic HIGH/LOW without external level shifters. This capability is confirmed in the Recommended Operating Conditions table and eliminates interface components in hybrid-voltage systems.

What is the recommended bypass capacitor for the SN74LV138APWRE4?

Texas Instruments recommends a 0.1-μF ceramic capacitor placed physically adjacent to the VCC pin (within 10 mm) and connected directly to the GND plane. This capacitor suppresses high-frequency supply noise generated by internal switching and ensures stable operation across the full –40°C to +85°C temperature range. For systems with significant noise coupling, paralleling a 1-μF capacitor improves low-frequency decoupling - a practice validated in TI's Layout Guidelines section for the SN74LV138APWRE4.

How many enable inputs does the SN74LV138APWRE4 have, and what are their polarities?

The SN74LV138APWRE4 has three enable inputs: G2 (active-HIGH), G0 (active-LOW), and G1 (active-LOW). All three must be asserted simultaneously for decoding to occur - i.e., G2 = HIGH and G0 = G1 = LOW. This asymmetric enable structure reduces external logic count when expanding to larger decoder trees; for example, a 24-line decoder requires zero external inverters, and a 32-line decoder needs only one. This configuration is fixed and cannot be reconfigured via pins or registers in the SN74LV138APWRE4.