Texas Instruments SN74LV138ADBR

Overview

SN74LV138ADBR 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 partial-power-down support, and mixed-mode voltage operation on 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 systems.

For engineers reviewing the SN74LV138ADBR datasheet, SN74LV138ADBR pinout, SN74LV138ADBR application, or SN74LV138ADBR equivalent, key selection criteria include VCC range compatibility (2–5.5 V), tpd ≤ 9.5 ns at 5 V, Ioff-enabled power-down behavior, active-low output polarity, and TSSOP-16 package footprint constraints.

Technical Context

The SN74LV138ADBR implements positive-logic 3-to-8 decoding 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 additional logic. Its CMOS input structure demands fast edge rates (≤20 ns/V at 5 V) to prevent oscillation, while balanced push-pull outputs drive up to ±12 mA at 5 V with defined VOL (0.55 V) and VOH (3.8 V) under load.

Functional mode control relies on simultaneous evaluation of all three enables: only when G2 = HIGH and G0 = G1 = LOW does the device decode A2:A0 to assert exactly one low output (Y0–Y7); all outputs remain HIGH otherwise. Ioff circuitry disables outputs and limits leakage to 5 µA when VCC = 0 V, supporting hot-insertion and partial-power-down system architectures.

Key Specifications

Pinout & Package

Packaged in a 16-pin TSSOP (PW), the SN74LV138ADBR measures 5.00 mm × 4.40 mm with 0.65 mm lead pitch and exposed thermal pad (not electrically connected). The body is RoHS-compliant and moisture-sensitive level 1 (MSL-1).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC138DR and SN74LVC138APWR, the SN74LV138ADBR uniquely balances 2–5.5 V flexibility, industrial temperature range, Ioff safety, and 9.5 ns speed-making it optimal for legacy 5 V designs needing modern power management and mixed-voltage robustness.

Availability

SN74LV138ADBR is available at Aetrix Electronics and suitable for memory decoding, LED matrix control, 7-segment display multiplexing, and 8-bit data storage enable applications requiring stable component supply across industrial and embedded product lifecycles.

Supply support for SN74LV138ADBR 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 SN74LV138ADBR belongs to TI's LV (Low-Voltage) logic family, engineered for interoperability across 2–5.5 V supply domains while maintaining speed, noise immunity, and power-down safety for industrial control and communications infrastructure.

FAQ

What is the maximum propagation delay of the SN74LV138ADBR at 3.3 V?

The SN74LV138ADBR 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 or enable input to any Y output under recommended operating conditions and ensures timing predictability in 3.3 V microcontroller interfaces. The SN74LV138ADBR maintains sub-15 ns performance even at elevated temperatures up to +85°C.

Does the SN74LV138ADBR support partial power-down operation?

Yes, the SN74LV138ADBR supports partial power-down via its Ioff feature, which disables all outputs and limits leakage current to ≤5 µA when VCC = 0 V. This prevents damaging current backflow when the device is unpowered but connected to live buses-a critical capability in modular systems and hot-swap architectures. The SN74LV138ADBR retains this behavior across its full –40°C to +85°C operating range.

What package type is used for the SN74LV138ADBR?

The SN74LV138ADBR uses a 16-pin TSSOP (Thin Shrink Small Outline Package), designated as PW in TI's packaging nomenclature, with dimensions of 5.00 mm × 4.40 mm and 0.65 mm lead pitch. It includes a non-electrical thermal pad for enhanced heat dissipation and complies with JEDEC MO-153 standards. The SN74LV138ADBR's TSSOP footprint is compatible with standard SMT reflow profiles and automated optical inspection.

Can the SN74LV138ADBR interface directly with 2.5 V and 5 V logic families?

Yes, the SN74LV138ADBR supports mixed-mode voltage operation: inputs tolerate voltages up to 5.5 V regardless of VCC, and output VOH/VOL specs are guaranteed across 2–5.5 V. This allows direct connection to 2.5 V FPGA I/O banks while powered from 3.3 V, or driving 5 V TTL inputs from a 5 V supply-no level shifters required. The SN74LV138ADBR's input thresholds scale with VCC (VIH ≥ 0.7×VCC), ensuring reliable recognition across voltage domains.

How many enable inputs does the SN74LV138ADBR have, and what are their polarities?

The SN74LV138ADBR has three enable inputs: G2 (active-HIGH) and G0/G1 (both active-LOW). All three must be asserted simultaneously-G2 = HIGH and G0 = G1 = LOW-for decoding to occur. This configuration reduces external logic count in multi-chip select schemes; for example, a 24-line decoder can be built using three SN74LV138ADBR devices without any added inverters. The SN74LV138ADBR's enable architecture is explicitly documented in its functional truth table and logic diagram.