NXP Semiconductors 74HC147D,653

Overview

74HC147D,653 from Nexperia (formerly Philips Semiconductors) 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 implicit "zero" encoding when all inputs are HIGH; operates at 5 V supply, 15 ns typical propagation delay, and supports industrial temperature range (−40 °C to +125 °C); used in keyboard encoding and switch matrix interfaces.

For engineers reviewing the 74HC147D,653 datasheet, 74HC147D,653 pinout, 74HC147D,653 application, or 74HC147D,653 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 DC/AC timing compliance per JEDEC 7A.

Technical Context

The 74HC147D,653 implements priority encoding using Si-gate CMOS technology, ensuring TTL-compatible pinout and voltage thresholds for HCT variants while maintaining HC-level power efficiency. It resolves input conflicts by selecting only the highest-priority active-LOW input (A8 > A7 > … > A0), suppressing lower-priority assertions without latching or clocking.

Encoding relies on combinational logic with no internal storage; output states are purely function of instantaneous input levels. The implied "zero" code (Y3–Y0 = HIGH) occurs exclusively when all nine data inputs are HIGH - a design feature enabling compact switch encoding without external pull-ups or zero-detection logic.

Key Specifications

Pinout & Package

74HC147D,653 is housed in a 16-pin SO16 (Small Outline) package per JEDEC MS-012, with 1.27 mm pitch and body size 10.0 × 4.4 mm. Pin 15 is internally unconnected (n.c.).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC147N and 74HCT147D,653, the 74HC147D,653 offers optimal balance of low input capacitance, fastest propagation in HC family, and SO16 footprint for modern SMT production - making it preferred for space-constrained, high-reliability embedded encoders.

Availability

74HC147D,653 is available at Aetrix Electronics and suitable for keypad interfaces, industrial control panels, legacy system upgrades, and BCD code generation requiring stable component supply across automotive, industrial, and medical electronics programs.

Supply support for 74HC147D,653 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

Nexperia is a global semiconductor expert delivering high-performance, reliable logic, analog, and discrete components with focus on efficiency and miniaturization.

The 74HC147D,653 belongs to Nexperia's 74HC high-speed CMOS logic family, designed specifically for low-power, pin-compatible replacements of legacy TTL encoders in industrial and automotive control systems.

FAQ

What is the logic polarity of inputs and outputs on the 74HC147D,653?

The 74HC147D,653 features active-LOW inputs (A0–A8) and active-LOW outputs (Y0–Y3). All inputs must be pulled HIGH when inactive; assertion occurs when driven LOW. Outputs reflect the encoded BCD value in active-LOW form - for example, decimal "5" yields Y3Y2Y1Y0 = LHLH. This polarity is fixed and cannot be inverted without external logic.

Does the 74HC147D,653 require external pull-up resistors on its inputs or outputs?

Yes - the 74HC147D,653 has no internal pull-ups. Inputs (A0–A8) must be externally pulled HIGH (e.g., 10 kΩ to VCC) when unused or open to ensure defined HIGH state. Outputs (Y0–Y3) are active-LOW and typically require pull-ups when driving TTL loads or LEDs; CMOS loads may operate without them depending on fan-out and trace capacitance.

How does the 74HC147D,653 handle the "zero" input condition?

The 74HC147D,653 encodes "zero" implicitly when all nine inputs (A0–A8) are HIGH - resulting in all four outputs (Y0–Y3) driven HIGH. This is not a dedicated input pin but a logical state derived from the absence of any active-LOW input, providing native detection of "no key pressed" or "all switches open" without additional circuitry.

Is the 74HC147D,653 pin-compatible with the 74LS147?

Yes - the 74HC147D,653 is fully pin-compatible with the 74LS147, sharing identical pin numbering, function assignment, and pinout configuration. This allows direct replacement in existing designs, though designers must verify VCC range (LS: 4.75–5.25 V; HC: 2.0–6.0 V) and adjust decoupling for CMOS switching characteristics.

What is the maximum operating frequency supported by the 74HC147D,653?

The 74HC147D,653 is a combinational logic device with no clock; its effective maximum operating frequency depends on propagation delay and system timing margins. With 15 ns typical tPHL/tPLH at 5 V, it supports reliable operation up to ≈33 MHz in ideal conditions - though real-world use in switch encoding rarely exceeds 10 kHz due to mechanical contact bounce limitations, not IC bandwidth.