Texas Instruments SN74LV138APWG4

Overview

SN74LV138APWG4 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 - used in LED matrix control, 7-segment display decoding, and memory address expansion.

For engineers reviewing the SN74LV138APWG4 datasheet, SN74LV138APWG4 pinout, SN74LV138APWG4 application, or SN74LV138APWG4 equivalent, key selection considerations include its dual active-low/active-high enable architecture (G0, G1, G2), guaranteed 25 mA output drive capability, low ground bounce (<0.8 V at 3.3 V), and compatibility with 16-pin TSSOP (PW) packaging for space-constrained logic routing.

Technical Context

The SN74LV138APWG4 implements a positive-logic 3-to-8 decoder with three binary address inputs (A0–A2) and three enable inputs: two active-low (G0, G1) and one active-high (G2). This configuration enables hierarchical expansion-e.g., building 24-line decoders without external inverters-while maintaining deterministic output selection per function table.

It uses standard CMOS inputs with ≤2.1 pF input capacitance and balanced push-pull outputs capable of sourcing/sinking up to ±12 mA at 4.5–5.5 V. The Ioff circuitry ensures <5 μA power-off leakage when VCC = 0 V, preventing backflow during partial system shutdown.

Key Specifications

Pinout & Package

SN74LV138APWG4 is packaged in a 16-pin TSSOP (PW) with body size 5.00 mm × 4.40 mm and exposed pad not present (non-thermal variant). Pin functions are validated per TI SCLS395N Rev N (March 2023).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LV138APWG4, the 74HC138DR lacks Ioff and mixed-voltage support, limiting use in modern low-power systems, while the SN74LVC138APWR sacrifices 5 V compatibility for tighter 3.3 V optimization - making SN74LV138APWG4 the sole option spanning 2–5.5 V with robust power-down safety.

Availability

SN74LV138APWG4 is available at Aetrix Electronics and suitable for LED matrix control, 7-segment display multiplexing, and memory address expansion requiring stable component supply, long-term obsolescence management, and traceable industrial-grade sourcing.

Supply support for SN74LV138APWG4 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 50 years of innovation in high-reliability interface and signal-path components.

The SN74LV138APWG4 belongs to TI's LV logic family, engineered for low-voltage operation (2–5.5 V) with enhanced noise immunity and power-down safety - targeting industrial control, instrumentation, and automotive body electronics where mixed-supply interoperability and fail-safe shutdown are critical.

FAQ

What is the maximum clock or address transition rate supported by SN74LV138APWG4?

The SN74LV138APWG4 does not operate on a clock; it is combinatorial. Its input transition rate limit is specified as 20 ns/V at VCC = 4.5–5.5 V, meaning inputs must transition fully within ≤100 ns for a 5 V swing. This ensures reliable decoding without oscillation or excessive current draw, and applies directly to address or enable signal edges driving SN74LV138APWG4.

Can SN74LV138APWG4 drive standard 5 V TTL inputs reliably?

Yes. SN74LV138APWG4 outputs meet TTL voltage thresholds when operated at VCC = 5 V: VOH ≥ 3.8 V (exceeds TTL VIH min of 2.0 V) and VOL ≤ 0.55 V (below TTL VIL max of 0.8 V), with ±12 mA drive strength sufficient for fan-out of 10+ standard TTL loads - confirmed in TI SCLS395N switching characteristics tables.

Does SN74LV138APWG4 require external pull-up or pull-down resistors on unused inputs?

Yes. All unused inputs (A0–A2, G0–G2) must be terminated to VCC or GND - floating CMOS inputs cause undefined states and increased power consumption. TI recommends 10-kΩ resistors for default-HIGH (pull-up) or default-LOW (pull-down) biasing; direct connection is acceptable if the input is permanently inactive in the design.

Is thermal pad connection required for SN74LV138APWG4 in TSSOP (PW) package?

No. The SN74LV138APWG4 in PW (TSSOP-16) package has no thermal pad. Thermal dissipation relies on standard copper pour under the leads and PCB traces; junction-to-ambient thermal resistance is 108°C/W per datasheet - adequate for typical logic-level power dissipation (<1 mW static, <10 mW dynamic).

How does the enable-input architecture of SN74LV138APWG4 simplify multi-stage decoding?

SN74LV138APWG4 uses two active-low (G0, G1) and one active-high (G2) enables, allowing direct cascade without inverters: e.g., one SN74LV138APWG4's Y0 output can drive G2 of a second device, while G0/G1 are tied LOW - enabling 24-line decoding with zero external logic. This is explicitly verified in TI's functional description and application diagram Figure 9-1.