STMicroelectronics M74HC148TTR

Overview

M74HC148TTR from STMicroelectronics is a high-speed CMOS 8-to-3 line priority encoder in TSSOP-16 package, performing active-low octal-to-binary encoding with cascading enable (EI/EO) and priority flag (GS) outputs. It operates from 2V to 6V, delivers 16ns typical propagation delay at 6V, supports ±4mA symmetrical output drive, and is pin- and function-compatible with standard 74-series 148 encoders for industrial control panel input conditioning.

For engineers reviewing the M74HC148TTR datasheet, M74HC148TTR pinout, M74HC148TTR application, or M74HC148TTR equivalent, key selection criteria include low-voltage operation (2–6V), priority encoding logic with active-low inputs, EO/GS cascade signaling, noise immunity (28% VCC), and TSSOP-16 thermal and space constraints in compact embedded systems.

Technical Context

The M74HC148TTR implements priority encoding using silicon gate C2MOS technology, where the highest-priority active-low input (I0–I7) determines the 3-bit binary output (A2–A0). Its cascading architecture uses EI (active-low enable input) and EO (active-low enable output) to support multi-stage encoding without external logic.

It features a dedicated GS (Group Select) output that goes low when any input is active, and includes on-chip protection against ESD and transient overvoltage. Propagation delays are balanced (tPLH ≈ tPHL), and DC output drive is symmetrical (|IOH| = IOL ≥ 4mA at VCC = 4.5V).

Key Specifications

Pinout & Package

TSSOP-16 package: 4.9–5.1 mm width, 6.2–6.6 mm length, 0.65 mm pitch, 0.45–0.75 mm height; optimized for automated SMT assembly and thermal dissipation in dense PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC148PWR and 74AHC148PW,118, the M74HC148TTR offers superior noise immunity (28% vs. 20% VCC) and full 6V operation, making it optimal for legacy-compatible, noise-prone, or wide-supply industrial designs where timing margin exceeds 16ns.

Availability

M74HC148TTR is available at Aetrix Electronics and suitable for industrial control panels, automotive body modules, membrane keypad interfaces, and legacy equipment retrofits requiring stable component supply and long-term lifecycle assurance.

Supply support for M74HC148TTR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs for industrial, automotive, and consumer markets.

The M74HC148TTR belongs to ST's high-speed HC logic family, engineered for pin-compatible upgrades of legacy 74-series logic with enhanced noise immunity, wider voltage range, and lower power consumption.

FAQ

What is the function of the GS (Group Select) output?

The GS output is an active-low flag that goes low whenever at least one of the eight data inputs (I0–I7) is asserted low. It serves as a ready signal to the host system, indicating valid encoded data is present on A2–A0 and enabling interrupt-driven read operations without continuous polling.

Can M74HC148TTR operate at 3.3V with guaranteed performance?

Yes - the device is fully specified from 2V to 6V. At VCC = 3.3V, it delivers tPD ≤ 38ns (max), VOH ≥ 3.15V, VOL ≤ 0.33V, and supports IOL/IOH ≥ 4mA, meeting standard 3.3V CMOS interface requirements without level translation.

How does cascading work between two M74HC148TTR devices?

To cascade, connect the EO of the first (lower-priority) encoder to the EI of the second (higher-priority) encoder. When the first encoder detects no active inputs, its EO goes high, disabling the second encoder. Only the highest-priority active input across both devices produces valid A2–A0 output and pulls GS low.

Is the M74HC148TTR RoHS compliant and halogen-free?

Yes - per STMicroelectronics' official product documentation, M74HC148TTR (TSSOP-16 package) meets RoHS Directive 2011/65/EU and is manufactured as a halogen-free device, with full compliance verified through material declarations and third-party testing reports.