Texas Instruments SN74LV138APW

Overview

SN74LV138APW from Texas Instruments is a 3-line to 8-line decoder/demultiplexer IC operating from 2 V to 5.5 V, featuring 9.5 ns maximum propagation delay at 5 V, Ioff-enabled partial-power-down capability, and mixed-mode voltage operation across all ports. It serves as a core address decoder in memory expansion and peripheral selection circuits for microcontroller-based embedded systems.

For engineers reviewing the SN74LV138APW datasheet, SN74LV138APW pinout, SN74LV138APW application, or SN74LV138APW equivalent, key selection considerations include its active-low G0/G1 and active-high G2 enable architecture, TSSOP-16 package footprint, 3.3 V/5 V logic compatibility, and output drive capability up to ±12 mA at 5 V.

Technical Context

The SN74LV138APW implements a positive-logic 3-to-8 decoding function where binary inputs A0–A2 select one of eight active-low outputs (Y0–Y7), conditioned by three enable signals: G2 (active-high) and G0/G1 (active-low). Its CMOS push-pull outputs support bidirectional current sourcing/sinking with balanced drive strength.

Functional mode control relies on strict enable hierarchy: all three enables must be asserted (G2 = H, G0 = L, G1 = L) for decoding; any enable violation forces all outputs high-impedance. The Ioff circuit ensures zero current backflow when VCC = 0 V, enabling hot-insertion and system-level power sequencing.

Key Specifications

Pinout & Package

TSSOP-16 package (PW), 5.00 mm × 4.40 mm body size, 0.65 mm lead pitch, exposed pad optional (not thermal pad 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 the 74HC138D, SN74LV138APW delivers faster timing and robust power-down safety; versus SN74LVC138APW, it trades minor VOL improvement for broader industrial temperature support (–40°C to 85°C same) and proven field reliability in TI's LV family.

Availability

SN74LV138APW is available at Aetrix Electronics and suitable for memory expansion, LED matrix control, 7-segment display multiplexing, and peripheral enable management requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for SN74LV138APW 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 SN74LV138APW belongs to TI's LV (Low-Voltage) logic family, engineered for reliable operation across 2 V–5.5 V supplies in industrial, automotive, and communications equipment where mixed-voltage interoperability and power sequencing integrity are essential.

FAQ

What is the maximum propagation delay of the SN74LV138APW at 3.3 V?

The SN74LV138APW has a maximum propagation delay of 13.5 ns at VCC = 3.3 V with a 15 pF load, as specified in Section 6.7 of the datasheet. This value applies to transitions from address inputs (A0–A2) or enable inputs (G0/G1/G2) to any output (Y0–Y7), ensuring predictable timing in 3.3 V digital systems.

Does the SN74LV138APW support partial power-down functionality?

Yes, the SN74LV138APW includes Ioff circuitry that disables all outputs when VCC = 0 V, limiting leakage current to ≤5 μA per I/O. This feature prevents current backflow in partially powered systems, making SN74LV138APW suitable for hot-swap applications and multi-rail power architectures where subsystems power up/down independently.

Can the SN74LV138APW interface directly between 5 V and 3.3 V logic domains?

Yes, the SN74LV138APW supports mixed-mode voltage operation: inputs tolerate up to 5.5 V regardless of VCC setting, allowing 5 V controllers to drive its A0–A2, G0–G2 pins while the device operates at 3.3 V. Outputs swing rail-to-rail (0 V to VCC), so SN74LV138APW outputs at 3.3 V are fully compatible with 3.3 V receivers.

What is the recommended bypass capacitor for the SN74LV138APW?

Texas Instruments recommends a 0.1 μF ceramic capacitor placed as close as possible to the VCC and GND pins of the SN74LV138APW. This minimizes high-frequency supply noise and stabilizes switching transients, especially critical given the device's fast 9.5 ns propagation delay and CMOS output drive characteristics.

How many enable inputs does the SN74LV138APW have, and what are their polarities?

The SN74LV138APW has three enable inputs: G2 is active-high, while G0 and G1 are active-low. All three must be simultaneously asserted (G2 = H, G0 = L, G1 = L) for decoding to occur; any deviation forces all Y0–Y7 outputs into high-impedance state. This architecture reduces external gate count when expanding to larger decoder configurations.