NXP Semiconductors 74HCT85D,653

Overview

74HCT85D,653 from Nexperia (formerly Philips Semiconductors) is a 4-bit magnitude comparator IC used to determine relative binary word size in digital logic systems. It accepts two 4-bit inputs (A0–A3, B0–B3), delivers mutually exclusive QA>B, QA=B, and QA<B outputs, features TTL-compatible input thresholds (VI = GND to 3 V), and operates at VCC = 4.5 V with typical propagation delays of 24–44 ns - enabling real-time comparison in servo-motor control and process controllers.

For engineers reviewing the 74HCT85D,653 datasheet, 74HCT85D,653 pinout, 74HCT85D,653 application, or 74HCT85D,653 equivalent, key selection criteria include cascading capability via IA>B/IA=B/IA<B expansion inputs, HCT-family 5 V TTL-level compatibility, standard-output drive strength, MSI integration level, and SO16 package suitability for space-constrained industrial logic boards.

Technical Context

The 74HCT85D,653 implements combinational logic for unsigned binary magnitude comparison using hierarchical feed-forward expansion architecture. Its three cascaded inputs (IA>B, IA=B, IA<B) enable serial or parallel chaining of multiple units to compare words beyond 4 bits without external gating.

Operation follows a deterministic truth table where outputs QA>B, QA=B, QA<B are mutually exclusive during normal single-device use, while the lower section defines feed-forward behavior required for correct multi-stage cascading - e.g., QA=B goes HIGH only when all four bit-pairs match AND IA=B is HIGH.

Key Specifications

Pinout & Package

74HCT85D,653 is housed in a 16-pin small-outline integrated circuit (SO16) package with 1.27 mm pitch, JEDEC MS-012AC compliant outline, and surface-mount footprint optimized for automated assembly and high-density PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-bit magnitude comparator applications.

Compared with SN74HCT85N and 74VHC85M, the 74HCT85D,653 uniquely balances TTL compatibility, SO16 manufacturability, and predictable 40–55 ns worst-case delay across industrial temperature - making it the default choice for new 5 V control logic designs requiring drop-in reliability.

Availability

74HCT85D,653 is available at Aetrix Electronics and suitable for industrial process controllers, servo-motor control systems, and digital test equipment requiring stable component supply, long-term lifecycle assurance, and consistent SO16 packaging across production batches.

Supply support for 74HCT85D,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 logic, discrete, and MOSFET solutions with focus on efficiency, reliability, and scalability for industrial and automotive markets.

The 74HCT85D,653 belongs to Nexperia's 74HCT logic family - engineered specifically for seamless 5 V TTL-to-CMOS interfacing in control, automation, and instrumentation systems where signal integrity and supply robustness are critical.

FAQ

What is the operating voltage range for the 74HCT85D,653?

The 74HCT85D,653 operates over a supply voltage range of 4.5 V to 5.5 V. This range ensures full compatibility with standard 5 V TTL systems while maintaining HCT-family input threshold specifications (VIH ≥ 2.0 V, VIL ≤ 0.8 V). Operation outside this window may cause invalid logic states or increased ICC, and the 74HCT85D,653 is not characterized for functionality below 4.5 V or above 5.5 V per its official Nexperia datasheet.

How does cascading work with the 74HCT85D,653 for comparing more than 4 bits?

Cascading the 74HCT85D,653 uses IA<B, IA=B, and IA>B inputs to accept results from a less-significant stage. For proper operation, the LSB device must have IA<B = IA>B = LOW and IA=B = HIGH. Subsequent stages connect their QA outputs to the next stage's IA inputs. The 74HCT85D,653's feed-forward logic ensures correct multi-bit comparison without external gates - verified in its function table and functional diagram.

Is the 74HCT85D,653 pin-compatible with the 74HC85 variant?

Yes, the 74HCT85D,653 is pin-compatible with the 74HC85, sharing identical pin configuration, terminal functions, and package outline. However, the 74HCT85D,653 uses TTL-compatible input thresholds (VIH = 2.0 V min), whereas the 74HC85 uses CMOS thresholds (VIH = 0.7×VCC). Interchanging them requires verifying source logic family - the 74HCT85D,653 is intended for 5 V TTL-driven systems.

What is the maximum propagation delay of the 74HCT85D,653 across its full temperature range?

The maximum propagation delay for the 74HCT85D,653 is 55 ns (An/Bn to QA>B or QA<B) and 50 ns (An/Bn to QA=B) over the industrial temperature range of −40°C to +85°C at VCC = 4.5 V. These values are specified in the official Nexperia AC characteristics table and define worst-case timing margins for synchronous system design using the 74HCT85D,653.

Does the 74HCT85D,653 support BCD or only binary comparison?

The 74HCT85D,653 supports both binary and BCD (binary-coded decimal) comparison, as confirmed in its General Description: "They perform comparison of two 4-bit binary, BCD or other monotonic codes." Its logic evaluates weighted bit positions (A0–A3, B0–B3), making it valid for any monotonic encoding - including BCD - provided inputs adhere to valid code rules. No configuration is needed; the 74HCT85D,653 performs the same function regardless of interpretation.