Texas Instruments SN74LV138ADR

Overview

SN74LV138ADR from Texas Instruments is a 3-line to 8-line decoder/demultiplexer IC operating from 2 V to 5.5 V, delivering 9.5 ns maximum propagation delay at 5 V, supporting mixed-mode voltage operation across all ports, and featuring Ioff for partial-power-down mode. It is used in output expansion circuits where precise address decoding and low-voltage compatibility are required.

For engineers reviewing the SN74LV138ADR datasheet, SN74LV138ADR pinout, SN74LV138ADR application, or SN74LV138ADR equivalent, key selection criteria include VCC range (2–5.5 V), tpd ≤ 9.5 ns at 5 V, active-low G0/G1 + active-high G2 enable architecture, Ioff support for power sequencing, and SOIC-16 package compatibility with standard PCB footprints.

Technical Context

The SN74LV138ADR implements a positive-logic 3-to-8 decoder with three binary address inputs (A0–A2) and three enable inputs (G2, G0, G1), where G0 and G1 are active-low and G2 is active-high-enabling direct cascading without external inverters. Its CMOS push-pull outputs drive up to ±12 mA at 4.5–5.5 V while maintaining VOL ≤ 0.55 V and VOH ≥ 3.8 V under load.

Designed for memory decoding and data routing, it features standard CMOS inputs with ≤2.1 pF input capacitance and supports partial-power-down via Ioff leakage control (<5 μA), preventing backflow when VCC = 0 V. All unused inputs must be terminated to VCC or GND to avoid floating-state oscillation.

Key Specifications

Pinout & Package

SN74LV138ADR is supplied in a 16-pin SOIC (D) package measuring 9.90 mm × 3.91 mm, with standard 1.27 mm pitch and gull-wing leads compatible with reflow soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC138DR and 74LVC138AD,118, the SN74LV138ADR uniquely balances 2–5.5 V operation, 9.5 ns speed at 5 V, and Ioff-enabled power sequencing-making it optimal for industrial controllers requiring robust voltage interoperability and safe power-up/down behavior.

Availability

SN74LV138ADR is available at Aetrix Electronics and suitable for output expansion, LED matrix control, and 7-segment display applications requiring stable component supply, long-term industrial lifecycle support, and consistent SOIC-16 packaging.

Supply support for SN74LV138ADR 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 specializing in analog and embedded processing technologies, with leadership in logic, power management, and signal chain solutions.

The SN74LV138ADR belongs to TI's LV (Low-Voltage) logic family, designed specifically for robust performance across wide VCC ranges (2–5.5 V) in industrial, automotive, and communications equipment where mixed-supply interoperability and power sequencing reliability are essential.

FAQ

What is the maximum propagation delay of the SN74LV138ADR at 3.3 V operation?

The SN74LV138ADR has a maximum propagation delay of 13.5 ns at VCC = 3.3 V with a 15 pF load, as specified in the switching characteristics table. This value applies to transitions from any address (A0–A2) or enable (G2, G0, G1) input to any Y0–Y7 output. The delay remains within specification across the full –40°C to +85°C operating temperature range, making SN74LV138ADR suitable for timing-critical industrial decoding tasks.

Does the SN74LV138ADR support partial-power-down mode, and how is it implemented?

Yes, the SN74LV138ADR supports partial-power-down mode via its Ioff feature. When VCC is at 0 V, the Ioff circuitry disables all outputs, limiting leakage current to <5 μA per I/O terminal regardless of input voltage. This prevents damaging current backflow during power sequencing or hot-swap events. The SN74LV138ADR maintains this behavior across its full rated temperature range, distinguishing it from non-Ioff logic families like HC or HCT.

Can the SN74LV138ADR be used in mixed-voltage systems, and what interfaces does it support?

Yes, the SN74LV138ADR supports mixed-mode voltage operation on all ports, allowing direct interfacing between 2.5 V, 3.3 V, and 5 V logic domains without level shifters. Its input thresholds scale with VCC (VIH = 0.7×VCC, VIL = 0.3×VCC), and outputs swing rail-to-rail. This capability is verified across all recommended operating conditions and makes SN74LV138ADR ideal for heterogeneous digital subsystems such as FPGA-to-peripheral bridges or multi-rail MCU expansions.

What is the recommended bypass capacitor for the SN74LV138ADR, and where should it be placed?

Texas Instruments recommends a 0.1 μF ceramic bypass capacitor placed physically adjacent to the SN74LV138ADR's VCC and GND pins-ideally within 2 mm trace length-to suppress high-frequency supply noise. The capacitor must connect directly to the IC's power pins with minimum loop area. For boards with multiple SN74LV138ADR units or noisy environments, paralleling a 1 μF capacitor improves low-frequency decoupling. Layout guidelines specify avoiding 90° corners and using ground flood fill to enhance noise immunity-critical for maintaining SN74LV138ADR's 9.5 ns timing accuracy.

Are unused inputs on the SN74LV138ADR required to be terminated, and if so, how?

Yes, all unused inputs on the SN74LV138ADR-including A0, A1, A2, G0, G1, and G2-must be terminated to either VCC or GND to prevent floating states that cause excessive power consumption, oscillation, or undefined output behavior. Direct connection is acceptable for permanently unused inputs; for intermittently used ones, a 10 kΩ pull-up or pull-down resistor is recommended. This requirement is explicitly stated in TI's application report "Implications of Slow or Floating CMOS Inputs" and applies to every SN74LV138ADR unit in operation.