Texas Instruments SN74LV138APWR

Overview

SN74LV138APWR 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 interface support. It selects one of eight active-low outputs using three binary address inputs (A0–A2) and three enable inputs (G0, G1 active-low; G2 active-high), commonly used in memory decoding and output expansion for microcontroller-based peripheral control.

For engineers reviewing the SN74LV138APWR datasheet, SN74LV138APWR pinout, SN74LV138APWR application, or SN74LV138APWR equivalent, key selection considerations include its 16-pin TSSOP package, guaranteed 3.3 V/5 V operation, ground-bounce and undershoot performance specs, Ioff leakage rating, and compatibility with standard CMOS logic families across supply voltages.

Technical Context

The SN74LV138APWR implements a positive-logic 3-to-8 decoder with three independent enable controls: two active-low (G0, G1) and one active-high (G2), enabling hierarchical expansion without external inverters. Its CMOS input structure requires fast edge rates (≤20 ns/V at 5 V) and mandates termination of unused inputs to VCC or GND.

Outputs are balanced push-pull with defined VOL (0.55 V max at 12 mA, 4.5 V) and VOH (3.8 V min at 12 mA, 4.5 V), supporting direct drive of LED segments or logic inputs. The Ioff feature disables all outputs when VCC = 0 V, limiting backflow current to ≤5 μA per terminal during partial power-down.

Key Specifications

Pinout & Package

Packaged in a 16-pin TSSOP (PW), the SN74LV138APWR measures 5.00 mm × 4.40 mm with 0.65 mm lead pitch and exposed thermal pad (not electrically connected in PW variant).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar decoder/demultiplexer applications.

Compared with 74HC138D and SN74LVC138APWR, the SN74LV138APWR uniquely balances 2–5.5 V flexibility, 9.5 ns speed at 5 V, and Ioff protection-making it optimal for mixed-supply industrial controllers where legacy 5 V peripherals coexist with modern 3.3 V logic.

Availability

SN74LV138APWR is available at Aetrix Electronics and suitable for memory decoding, LED matrix control, 7-segment display multiplexing, and 8-bit data latching requiring stable component supply across automotive infotainment, industrial HMI, and test equipment designs.

Supply support for SN74LV138APWR 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 high-reliability, production-grade ICs.

The SN74LV138APWR belongs to TI's LV logic family, engineered for low-voltage, high-speed operation across mixed-supply systems-designed specifically for memory expansion, peripheral selection, and signal routing in space-constrained industrial and automotive applications.

FAQ

What is the maximum operating temperature range for the SN74LV138APWR?

The SN74LV138APWR is rated for operation from –40°C to +85°C ambient temperature, fully specified across this industrial temperature range per its Recommended Operating Conditions. This allows deployment in harsh environments such as factory automation panels or automotive under-hood modules where thermal stability is critical. All electrical characteristics-including propagation delay, VOL, and VOH-are guaranteed within this range.

Does the SN74LV138APWR support 2.5 V operation, and what are the timing implications?

Yes, the SN74LV138APWR supports 2.5 V ± 0.25 V operation with verified switching characteristics: tpd is 11.7–21 ns (typ/max) at CL = 15 pF. At this voltage, output drive strength reduces (IOL = 2 mA max), but logic thresholds remain valid (VIL ≤ 0.75 V, VIH ≥ 1.75 V). This makes SN74LV138APWR suitable for battery-powered IoT nodes where 2.5 V rail optimization is required.

How does the Ioff feature of the SN74LV138APWR protect system-level power sequencing?

The Ioff feature in the SN74LV138APWR disables all outputs when VCC = 0 V, limiting leakage current to ≤5 μA per pin. This prevents back-driving of powered-down sections-critical in modular systems where FPGA banks or MCU peripherals power up/down independently. Unlike standard logic, SN74LV138APWR avoids latch-up risk during hot-plug events without external isolation circuitry.

Can unused inputs on the SN74LV138APWR be left floating, and what is the recommended termination?

No, unused inputs on the SN74LV138APWR must never be left floating due to CMOS input structure. TI specifies termination to either VCC or GND via direct connection or 10-kΩ pull-up/pull-down resistors. Floating inputs cause excessive ICC, oscillation, and potential device damage. For example, unconnected G1 should be tied to VCC to disable the decoder unless actively used.

What is the capacitive load limit for reliable operation of the SN74LV138APWR outputs?

The SN74LV138APWR is characterized up to 50 pF load capacitance-beyond which propagation delay increases and VOLP/VOHV margins degrade. TI recommends keeping total output node capacitance ≤50 pF (including trace, probe, and input capacitance of driven devices) to meet datasheet timing and noise specs. For heavier loads, buffer stages or slew-rate controlled drivers should be added externally.