Texas Instruments SN74LV138APWT

Overview

SN74LV138APWT 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 support for partial-power-down mode, and mixed-mode voltage operation across all ports. It serves as a core address decoder in memory expansion and peripheral selection circuits within industrial control and embedded microcontroller systems.

For engineers reviewing the SN74LV138APWT datasheet, SN74LV138APWT pinout, SN74LV138APWT application, or SN74LV138APWT equivalent, key selection criteria include its active-low G0/G1 and active-high G2 enable architecture, guaranteed 8-output decoding under 5.5 V supply, and TSSOP-16 package compatibility with high-density PCB layouts.

Technical Context

The SN74LV138APWT implements standard CMOS logic with balanced push-pull outputs capable of sourcing/sinking up to ±12 mA at 5 V. Its three binary select inputs (A0–A2) and three enable inputs (G2, G0, G1) determine one active-low output among Y0–Y7, with all other outputs held high when enabled or all outputs high-impedance when disabled.

It supports partial-power-down via Ioff circuitry that disables outputs and limits leakage to ≤5 μA when VCC = 0 V, enabling safe hot-insertion in backplane or modular systems. The device meets JESD17 latch-up immunity (>250 mA) and operates across –40°C to +85°C.

Key Specifications

Pinout & Package

Packaged in a 16-pin TSSOP (PW), the SN74LV138APWT measures 5.00 mm × 4.40 mm with 0.65 mm lead pitch and exposed thermal pad (non-electrical) in RGY/BQB variants only - not applicable to PW.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC138DR and SN74LVC138APW, the SN74LV138APWT offers optimal balance of speed (9.5 ns), Ioff-enabled power management, and industrial temperature range (–40°C to +85°C), making it ideal for space-constrained, thermally demanding embedded controllers where both timing and sequencing integrity are critical.

Availability

SN74LV138APWT is available at Aetrix Electronics and suitable for memory expansion, LED matrix control, 7-segment display interfaces, and 8-bit data storage applications requiring stable component supply and long-term industrial lifecycle support.

Supply support for SN74LV138APWT 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 emphasis on reliability, precision, and energy efficiency.

The SN74LV138APWT belongs to TI's LV logic family, engineered for low-voltage operation (2–5.5 V) with enhanced noise immunity and power-down safety - specifically targeting industrial automation, test equipment, and programmable logic interfaces.

FAQ

What is the maximum propagation delay of the SN74LV138APWT at 3.3 V?

The SN74LV138APWT 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 any address or enable input (A0–A2, G0–G2) to any output (Y0–Y7). At 50 pF load, the max tpd increases to 18 ns - critical for timing budget allocation in high-speed decoding paths.

Does the SN74LV138APWT support partial-power-down mode?

Yes, the SN74LV138APWT 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 I/O terminal. This prevents current backflow in systems with unpowered sections, such as modular backplanes or hot-swappable I/O cards - a capability not present in standard HC or HCT logic families.

What package type does the SN74LV138APWT use?

The SN74LV138APWT uses a 16-pin TSSOP (Thin Shrink Small Outline Package), designated as PW in TI's packaging nomenclature. Its dimensions are 5.00 mm × 4.40 mm with 0.65 mm lead pitch. Unlike RGY or BQB variants, the PW package does not include a thermal pad, simplifying PCB layout while maintaining thermal performance up to 85°C ambient.

Can the SN74LV138APWT drive LEDs directly?

Yes, the SN74LV138APWT can drive LEDs directly in common-anode configurations, as each output sinks up to 12 mA at 4.5 V (VOL ≤0.55 V). For typical red/green LEDs with 1.8–2.2 V forward voltage, a series resistor of ~220 Ω ensures safe operation at 3.3 V supply. However, sustained 12 mA per output across all eight lines exceeds the device's total continuous current rating (±50 mA), so duty cycling or current limiting is recommended for full-row activation.

How does the enable logic work on the SN74LV138APWT?

The SN74LV138APWT uses three enable inputs: G2 (active-high) and G0/G1 (active-low). All three must be asserted simultaneously - G2 = HIGH, G0 = LOW, G1 = LOW - for decoding to occur. If any enable is inactive, all outputs go HIGH. This architecture allows hierarchical expansion: e.g., two SN74LV138APWT devices can implement a 4-to-16 decoder using one device's outputs to control G2 of the second, eliminating external inverters.