NXP Semiconductors 74HCT42N,652

Overview

74HCT42N,652 from Nexperia is a high-speed CMOS BCD-to-decimal decoder (1-of-10) with active LOW outputs, 4-bit BCD input (A0–A3), 10 mutually exclusive decoded outputs (Y0–Y9), and TTL-compatible input thresholds. It operates at 4.5 V to 5.5 V, delivers 17 ns typical propagation delay at VCC = 4.5 V, and disables all outputs for invalid BCD codes (10–15), enabling reliable address decoding in digital control panels.

For engineers reviewing the 74HCT42N,652 datasheet, 74HCT42N,652 pinout, 74HCT42N,652 application, or 74HCT42N,652 equivalent, key selection criteria include its active LOW output logic, HCT-level input compatibility with 3 V logic families, 1-of-8 demultiplexing capability via A3 inhibit, and guaranteed output disable above decimal 9 - critical for error-resistant BCD-driven display and memory select systems.

Technical Context

The 74HCT42N,652 implements a fixed-function combinational logic decoder with no internal latching or clocking. Its logic diagram confirms that outputs Y0–Y9 are driven LOW only for valid BCD inputs (0000–1001), while all outputs go HIGH for inputs 1010–1111, providing inherent invalid-code rejection.

It supports 1-of-8 demultiplexing by using A3 as an enable/data input: when A3 = HIGH, only Y8–Y9 are active; when A3 = LOW, Y0–Y7 respond to A2–A0, enabling compact 3-to-8 expansion without external gating.

Key Specifications

Pinout & Package

74HCT42N,652 is supplied in a 16-pin dual in-line package (DIP) with 0.3-inch body width and through-hole mounting. Pin 1 is located at the top-left corner adjacent to the notch or dot marking.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar BCD-to-decimal decoder applications.

Compared with SN74HCT42N and 74HCT42D,653, the 74HCT42N,652 offers identical functional behavior and timing in a legacy-compatible DIP package, making it optimal for prototyping, repair, and low-volume industrial control boards where manual assembly or socketing is required.

Availability

74HCT42N,652 is available at Aetrix Electronics and suitable for industrial control panels, legacy microprocessor address decoding, and BCD-driven LED display systems requiring stable component supply over extended product lifecycles.

Supply support for 74HCT42N,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

Nexperia is a global leader in high-volume production of logic, discrete, and power MOSFET semiconductors, serving automotive, industrial, computing, and consumer markets with AEC-Q101 qualified components.

The 74HCT42N,652 belongs to Nexperia's 74HCT logic family, engineered for TTL-compatible interfacing in industrial and legacy digital systems where reliability, consistent timing, and long-term supply stability are essential.

FAQ

What is the maximum operating temperature range for the 74HCT42N,652?

The 74HCT42N,652 is rated for operation from −40 °C to +125 °C. This extended industrial temperature range ensures reliable performance in harsh environments such as factory automation controllers and outdoor instrumentation. All AC and DC specifications in the datasheet are guaranteed across this full range, with propagation delay remaining within 44 ns max at +125 °C and VCC = 4.5 V. The 74HCT42N,652 maintains consistent output drive strength and input threshold behavior throughout.

Does the 74HCT42N,652 support 3.3 V logic inputs?

No, the 74HCT42N,652 does not guarantee correct operation with 3.3 V logic inputs. Its HCT input thresholds require VIH ≥ 2.0 V and VIL ≤ 0.8 V, which aligns with 5 V TTL levels - not 3.3 V CMOS. Applying 3.3 V HIGH signals risks marginal or incorrect recognition. For mixed-voltage systems, level translation (e.g., TXB0104) or use of 74LVC42 is recommended. The 74HCT42N,652 must be powered at 4.5–5.5 V and driven by 5 V-compatible sources.

Can the 74HCT42N,652 be used as a 1-of-8 decoder without modification?

Yes, the 74HCT42N,652 can operate as a 1-of-8 decoder by using A3 as an enable signal: tie A3 LOW to activate Y0–Y7 for A2–A0 inputs, or tie A3 HIGH to activate only Y8 and Y9. This is explicitly supported in the functional description and logic diagram. No external components are needed - the 74HCT42N,652 inherently provides this capability due to its internal gate structure, making it suitable for address expansion where only eight outputs are required.

What happens when invalid BCD codes (10–15) are applied to the 74HCT42N,652 inputs?

When binary inputs 1010 through 1111 (decimal 10–15) are applied, the 74HCT42N,652 forces all ten outputs (Y0–Y9) HIGH. This behavior is hardwired in the logic design and confirmed in the function table. It prevents erroneous activation of downstream devices - for example, avoiding false digit selection in display systems or unintended peripheral enablement in address decoding. The 74HCT42N,652 requires no external blanking circuitry to achieve this safety feature.

Is the 74HCT42N,652 pin-compatible with older 74LS42 devices?

Yes, the 74HCT42N,652 is pin-compatible with 74LS42 and functionally compatible with identical pin assignments (A0–A3, Y0–Y9, VCC, GND). However, it is not electrically drop-in: the 74HCT42N,652 draws significantly less quiescent current, has higher noise immunity, and features CMOS input impedance. While it interfaces directly with LS-TTL outputs, LS drivers may not reliably drive HCT inputs at full speed without verifying fan-out. The 74HCT42N,652 replaces 74LS42 in upgrades seeking lower power and improved noise margin.