Texas Instruments SN74HC148DE4

Overview

SN74HC148DE4 from Texas Instruments is an 8-line to 3-line priority encoder IC used in digital logic systems to compress eight active-low data inputs into a 3-bit binary output (A2–A0), with built-in enable input (EI) and enable output (EO) for cascading. It operates from 2V to 6V, delivers ±4-mA output drive at 5V, exhibits typical propagation delay of 16ns, and draws ≤80 μA supply current - ideal for low-power address encoding in industrial control panels and keyboard scan circuits.

For engineers reviewing the SN74HC148DE4 datasheet, SN74HC148DE4 pinout, SN74HC148DE4 application, or SN74HC148DE4 equivalent, key selection considerations include its active-low input/output logic, cascading capability via EI/EO, SOIC-16 package compatibility, and guaranteed operation across –40°C to +85°C industrial temperature range.

Technical Context

The SN74HC148DE4 implements combinational priority encoding where only the highest-order asserted (low) input determines the output code; all lower-priority inputs are masked. Its functional modes include enabled encoding (EI = L), disabled output (EI = H), and cascaded operation where EO signals chain to downstream encoders' EI pins.

It uses standard CMOS technology with TTL-compatible output drive, supports fan-out of up to 10 LSTTL loads, and features low input current (≤1 μA) and low power dissipation (Cpd = 35 pF), making it suitable for noise-sensitive, battery-backed, or multi-stage logic systems requiring deterministic response to asynchronous input events.

Key Specifications

Pinout & Package

SN74HC148DE4 is housed in a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with standard 1.27-mm pitch and gull-wing leads compatible with automated SMT assembly and IPC-7351 land patterns.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar priority encoding applications.

Compared with SN74LS148N and CD74HC148E, the SN74HC148DE4 uniquely balances low power, wide voltage operation, and surface-mount readiness - making it optimal for new industrial and IoT edge designs where thermal management, supply flexibility, and automated assembly are priorities.

Availability

SN74HC148DE4 is available at Aetrix Electronics and suitable for industrial control panels, keyboard scan interfaces, and fault prioritization circuits requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74HC148DE4 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 industrial, automotive, and communications markets.

The SN74HC148DE4 belongs to TI's 74HC logic family, designed specifically for high-speed, low-power, pin-compatible replacements of legacy TTL logic in space-constrained and thermally sensitive applications.

FAQ

What is the operating voltage range for SN74HC148DE4?

The SN74HC148DE4 operates from 2 V to 6 V DC, supporting both 3.3 V and 5 V logic domains without level translation. This wide range allows direct integration into mixed-supply systems and battery-powered applications where voltage may drift between 2.7 V and 5.5 V during discharge cycles. The device maintains full functionality-including specified propagation delay and output drive-across this entire range per TI's recommended operating conditions table.

How does SN74HC148DE4 handle multiple simultaneous low inputs?

The SN74HC148DE4 resolves multiple simultaneous low inputs using strict priority encoding: only the highest-numbered asserted input (I7 > I6 > … > I0) determines the A2–A0 output code, while lower-priority inputs are ignored. This behavior is hardwired in the logic design and ensures deterministic output regardless of input transition timing - critical for reliable interrupt arbitration and keypad scanning where bounce or overlap occurs.

Can SN74HC148DE4 be used in cascaded configurations?

Yes, SN74HC148DE4 supports native cascading via dedicated EI (Enable Input) and EO (Enable Output) pins. When EI is low, the device encodes its inputs and drives EO low only if all eight inputs are high - allowing EO of one stage to serve as EI for the next. This eliminates external logic gates and enables scalable N-input priority encoding (e.g., two SN74HC148DE4 units form a 16-to-4 encoder), preserving timing integrity and reducing interconnect complexity.

What is the function of the GS (Group Select) pin on SN74HC148DE4?

The GS (Group Select) pin on SN74HC148DE4 is an active-low output that goes low whenever at least one input (I0–I7) is asserted low - indicating valid encoding activity. It serves as a ready/strobe signal to synchronize downstream logic (e.g., latching A2–A0 into a register) or trigger interrupts in microcontrollers. Unlike EO, GS does not depend on EI state and remains valid even when the encoder is disabled, providing robust status feedback independent of enable control.

Is SN74HC148DE4 compatible with 3.3 V microcontrollers?

Yes, SN74HC148DE4 is fully compatible with 3.3 V microcontrollers: its 2 V to 6 V supply range includes 3.3 V nominal operation, and its CMOS inputs accept VIH ≥ 2.0 V (at VCC = 3.3 V) and VIL ≤ 0.99 V - well within standard 3.3 V logic thresholds. Outputs swing rail-to-rail, delivering >3.0 V VOH and <0.1 V VOL, ensuring noise-immune communication with ARM Cortex-M or similar MCUs without level-shifting circuitry.