NXP Semiconductors 74HC147N,652

Overview

74HC147N,652 from NXP Semiconductors (formerly Philips) is a 10-to-4 line priority encoder IC that converts nine active-LOW decimal inputs (A0–A8) into four active-LOW BCD outputs (Y0–Y3), with A8 assigned highest priority and "zero" encoded when all inputs are HIGH; operates at VCC = 2.0–6.0 V; propagation delay tPHL/tPLH = 18 ns (typ.) at 5 V; standard output drive capability; used in switch encoding and code conversion systems.

For engineers reviewing the 74HC147N,652 datasheet, 74HC147N,652 pinout, 74HC147N,652 application, or 74HC147N,652 equivalent, key selection considerations include active-LOW input/output logic polarity, priority encoding behavior under multiple simultaneous inputs, BCD output compatibility with downstream decoders, and CMOS-level voltage tolerance across industrial temperature range (−40 °C to +125 °C).

Technical Context

The 74HC147N,652 implements priority encoding using Si-gate CMOS technology, ensuring pin compatibility with LSTTL while delivering lower power consumption and higher noise immunity. Its logic design assigns fixed priority (A8 > A7 > … > A0), resolving contention by selecting only the highest-priority asserted input.

Encoding relies on implied decimal "zero": all outputs go HIGH only when all nine inputs are HIGH - no dedicated "zero" input pin exists. Outputs are active LOW and fully compatible with standard 74HC-series fan-out requirements (IOH/ IOL ≥ ±4 mA at VCC = 4.5 V).

Key Specifications

Pinout & Package

74HC147N,652 is supplied in a 16-pin plastic dual-in-line package (DIP) with through-hole mounting. Pin 15 is not connected (n.c.). GND (pin 8) and VCC (pin 16) are located on opposite sides for noise reduction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC147N,652, the 74HCT147N,652 eases integration into legacy TTL environments, while SN74HC147N provides second-source assurance without design change - both retain identical priority logic, BCD output format, and DIP-16 footprint.

Availability

74HC147N,652 is available at Aetrix Electronics and suitable for industrial control panels, legacy system upgrades, and keypad interface designs requiring stable component supply, long-lifecycle support, and RoHS-compliant through-hole logic.

Supply support for 74HC147N,652 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

NXP Semiconductors is a global semiconductor leader specializing in secure connectivity solutions, automotive MCUs, and high-reliability logic families derived from Philips' legacy IC portfolio.

The 74HC147N,652 belongs to the 74HC/HCT logic family designed for robust, low-power, pin-compatible replacements of bipolar TTL in industrial, instrumentation, and control applications.

FAQ

What is the logic polarity of inputs and outputs on the 74HC147N,652?

The 74HC147N,652 uses active-LOW logic: all nine decimal inputs (A0–A8) and all four BCD outputs (Y0–Y3) are asserted when driven LOW. The "zero" state occurs when all inputs are HIGH, forcing all outputs HIGH. This polarity allows direct connection to mechanical switches pulled HIGH via resistors - a common configuration in industrial panel design.

Does the 74HC147N,652 require external pull-up resistors on its inputs?

Yes - the 74HC147N,652 inputs are active LOW and have high-impedance CMOS structure. Unused inputs must be tied HIGH (e.g., via 10 kΩ pull-ups to VCC) to prevent floating states that cause erratic encoding. Used inputs driven by open-collector or mechanical switches also require pull-ups to ensure defined HIGH levels when inactive.

Can the 74HC147N,652 encode a true decimal "zero" without asserting any input line?

Yes - the 74HC147N,652 encodes "zero" implicitly when all nine inputs (A0–A8) are HIGH. No dedicated "zero" input pin exists. This design eliminates one physical switch or signal line, simplifying front-panel layouts and reducing wiring complexity in applications like rotary selector switches or keypad "0" positions.

What is the maximum operating frequency supported by the 74HC147N,652?

The 74HC147N,652 does not specify a clock frequency, as it is asynchronous. Its usable event rate depends on propagation delay: tPHL/tPLH = 18 ns (typ.) at 5 V, supporting reliable encoding of input transitions occurring no faster than ~25 MHz. For mechanical switch applications, this margin exceeds typical bounce durations by >100×.

Is the 74HC147N,652 pin-compatible with older TTL versions like 74LS147?

Yes - the 74HC147N,652 is pin-compatible with 74LS147 and other 74xx147 variants. It retains identical pin numbering, function mapping, and DIP-16 footprint. However, note that 74HC147N,652 uses CMOS input thresholds and draws significantly less quiescent current, enabling direct replacement in most legacy designs without layout changes.