NXP Semiconductors 74HCT147D,653

Overview

74HCT147D,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; propagation delay is 35 ns typical at VCC = 4.5 V, output capability is standard, and it operates over −40 °C to +85 °C for industrial switch encoding applications.

For engineers reviewing the 74HCT147D,653 datasheet, 74HCT147D,653 pinout, 74HCT147D,653 application, or 74HCT147D,653 equivalent, key selection considerations include active-LOW input/output logic polarity, priority encoding behavior under multiple simultaneous inputs, BCD output compatibility with downstream TTL/CMOS decoders, and HCT-level 5 V CMOS/TTL interface compatibility.

Technical Context

The 74HCT147D,653 implements priority encoding using Si-gate CMOS technology with TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max), enabling direct interfacing with legacy LSTTL systems. Its logic function encodes nine active-LOW inputs into four active-LOW BCD outputs, where "zero" is implied when all inputs are HIGH.

Propagation delay (tPHL/tPLH) is specified at 35 ns typical (4.5 V, CL = 50 pF), and output transition time (tTHL/tTLH) is 15 ns typical under same conditions. The device belongs to the MSI (Medium Scale Integration) category and features standard output drive capability (±4 mA at VCC = 4.5 V).

Key Specifications

Pinout & Package

74HCT147D,653 is housed in a 16-pin SO16 (Small Outline) package per JEDEC MS-012, with 1.27 mm pitch, body width 3.9 mm, and lead count matching standard DIP-16 footprint for surface-mount compatibility.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS147N and 74HC147D,653, the 74HCT147D,653 uniquely balances TTL input compatibility, moderate speed (35 ns), and low power consumption (ICC < 8 µA), making it optimal for upgrading legacy systems while preserving signal integrity across mixed-logic environments.

Availability

74HCT147D,653 is available at Aetrix Electronics and suitable for industrial keypad encoders, BCD code converters, legacy system interface adapters, and diagnostic panel logic requiring stable component supply and long-term manufacturability.

Supply support for 74HCT147D,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 rooted in Philips' heritage of industrial-grade reliability and automotive qualification standards.

The 74HCT147D,653 belongs to Nexperia's 74HCT logic family, engineered specifically for seamless interoperability between 5 V TTL and modern CMOS systems in industrial control, instrumentation, and human-machine interface applications.

FAQ

What is the logic polarity of inputs and outputs on the 74HCT147D,653?

The 74HCT147D,653 uses active-LOW logic for both inputs and outputs: A0–A8 are active-LOW decimal inputs, and Y0–Y3 are active-LOW BCD outputs. This means a logic LOW on any input indicates assertion, and encoded values appear as LOWs on corresponding output lines - e.g., input A2 asserted yields Y1 and Y0 LOW (0010₂ = 2). This polarity is fixed and cannot be inverted internally.

Does the 74HCT147D,653 require external pull-up resistors on its inputs?

No, the 74HCT147D,653 does not require external pull-up resistors on its inputs when used with open-collector or mechanical switch sources. Its TTL-compatible inputs have defined thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V), and internal structure allows direct connection to grounded switches. However, if inputs float, undefined states may occur - proper termination (pull-up or pull-down) remains a system-level design requirement outside the 74HCT147D,653 itself.

How does the 74HCT147D,653 handle the "zero" input condition?

The 74HCT147D,653 encodes "zero" implicitly: when all nine inputs A0–A8 are HIGH, all four outputs Y0–Y3 go HIGH. This is not a dedicated input pin but a functional outcome of the priority logic - no input is active, so the default encoded value is decimal 0 (BCD 0000), represented as HIGHs on all outputs. This behavior is confirmed in the function table and enables "no-key-pressed" detection in encoder applications.

Is the 74HCT147D,653 pin-compatible with the 74LS147?

Yes, the 74HCT147D,653 is pin-compatible with the 74LS147 and other members of the 74xx147 family, including identical pin numbering, function assignment, and SO16/DIP16 footprints. This allows direct replacement in existing layouts without PCB modification, provided supply voltage and loading conditions remain within HCT specifications (4.5–5.5 V, standard output drive).

What is the maximum clock/data rate supported by the 74HCT147D,653?

While the 74HCT147D,653 is combinational (not clocked), its usable data rate is governed by propagation delay: 35 ns typical (4.5 V, CL = 50 pF) implies a maximum reliable toggle rate near 10–12 MHz under ideal conditions. Real-world performance depends on input rise/fall times, load capacitance, and noise margins - for robust operation in switch encoding, frequencies below 1 MHz are recommended to ensure setup/hold stability and contact bounce tolerance.