Texas Instruments SN74HC148AN

Overview

SN74HC148AN from Texas Instruments is an 8-line to 3-line priority encoder IC in PDIP-16 package, performing active-low octal-to-binary encoding with cascading capability via EI/EO pins. It operates from 2V to 6V, delivers ±4-mA output drive at 5V, and achieves typical propagation delay of 16ns at VCC = 4.5V - used in industrial control panels for compact address encoding of push-button arrays.

For engineers reviewing the SN74HC148AN datasheet, SN74HC148AN pinout, SN74HC148AN application, or SN74HC148AN equivalent, key selection criteria include its active-low input/output logic, 16-pin DIP mechanical compatibility, cascading support without external gates, and guaranteed operation across –40°C to +85°C industrial temperature range.

Technical Context

The SN74HC148AN implements combinational priority encoding where only the highest-order asserted (low) input among I0–I7 determines the 3-bit binary output A2–A0. Its functional modes are fully defined by the enable input (EI) and enable output (EO), enabling multi-stage expansion while maintaining strict low-level assertion for all data and control signals.

Internal logic ensures that GS (Group Select) goes low when any input is active, and EO goes low only when EI is low and all inputs are high - providing unambiguous status signaling for system-level arbitration and interrupt prioritization in microcontroller peripheral interfaces.

Key Specifications

Pinout & Package

SN74HC148AN uses a 16-pin plastic dual in-line package (PDIP) with 19.31 mm × 6.35 mm body size and 2.54 mm lead pitch. Pin 1 is marked by a notch or dot; leads are tin-lead (NIPDAU) finish, RoHS-compliant, and rated for through-hole reflow or wave soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS148N and CD74HC148E, the SN74HC148AN uniquely combines PDIP-16 mechanical compatibility, wide 2–6V supply flexibility, and sub-20ns propagation delay - making it the optimal choice for industrial upgrades requiring both legacy socket support and modern power efficiency.

Availability

SN74HC148AN is available at Aetrix Electronics and suitable for industrial control panels, microcontroller interrupt arbiters, legacy bus interfaces, and automated test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74HC148AN 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, embedded processing, and connectivity solutions for industrial, automotive, and consumer applications.

The SN74HC148AN belongs to TI's 74HC logic family - engineered for high-speed, low-power, wide-supply-voltage operation in industrial control, instrumentation, and legacy system modernization.

FAQ

What is the maximum clock frequency supported by SN74HC148AN?

The SN74HC148AN is a combinational logic device with no internal clock - it responds asynchronously to input changes. Its usable operating frequency depends on propagation delay and system timing margins: at VCC = 4.5V, typical tpd is 16ns, supporting reliable operation in digital systems with signal transitions up to ~30 MHz. The SN74HC148AN does not have a specified maximum clock rate because it lacks sequential elements or clock inputs.

Can SN74HC148AN be used with a 3.3V microcontroller?

Yes, the SN74HC148AN operates reliably from 2V to 6V, including 3.3V nominal supply. At VCC = 3.3V, VIH is guaranteed ≥2.3V and VIL ≤0.99V, ensuring clean interfacing with standard 3.3V CMOS outputs. The SN74HC148AN maintains full logic margin and output drive capability (≥±3 mA) at this voltage, making it suitable for mixed-voltage systems without level shifters.

How does cascading work with multiple SN74HC148AN devices?

Cascading uses EI (Enable Input) and EO (Enable Output): the EO of a higher-priority stage connects to the EI of the next stage. When the first SN74HC148AN detects an active input, its EO stays high, disabling downstream encoders. Only if all inputs to the first SN74HC148AN are inactive (high) does EO go low, enabling the second SN74HC148AN to respond - preserving strict priority order across 16+ inputs.

Is SN74HC148AN pin-compatible with older 74LS148 devices?

Yes, the SN74HC148AN is functionally and pinout-compatible with the 74LS148 in PDIP-16 packaging, sharing identical pin assignments for EI, I0–I7, A2–A0, GS, EO, VCC, and GND. However, due to HC-series CMOS characteristics, users must verify pull-up resistor values and ensure unused inputs are tied to VCC or GND - unlike LS TTL, which tolerates floating inputs less safely.

What is the purpose of the GS (Group Select) output on SN74HC148AN?

The GS output on SN74HC148AN is an active-low signal that goes low whenever at least one of the eight inputs (I0–I7) is asserted (low). It serves as a ready/busy indicator for downstream logic - commonly used to strobe the A2–A0 outputs or trigger a microcontroller interrupt. Unlike EO, GS is independent of EI state, providing immediate notification of valid input activity regardless of cascade enable status.