NXP Semiconductors 74HCT4538N,112

Overview

74HCT4538N,112 from Nexperia is a dual retriggerable precision monostable multivibrator in 16-lead DIP package, operating from 4.5 V to 5.5 V supply, delivering ±0.2 % pulse width stability over temperature, with 0.7 × REXT × CEXT timing accuracy and Schmitt-trigger inputs tolerant of slow edges. It serves as a precise one-shot timer in digital control, pulse shaping, and debouncing circuits.

For engineers reviewing the 74HCT4538N,112 datasheet, 74HCT4538N,112 pinout, 74HCT4538N,112 application, or 74HCT4538N,112 equivalent, key selection criteria include its dual independent monostable architecture, edge-trigger flexibility (rising or falling), direct active-low reset per channel, external R/C timing programmability, and guaranteed operation across -40 °C to +125 °C.

Technical Context

The 74HCT4538N,112 implements two fully independent retriggerable-resettable monostables, each with dual trigger inputs (nA for falling-edge, nB for rising-edge), dedicated active-low reset (nCD), complementary outputs (nQ/nQ), and separate REXT/CEXT timing node pairs. Its linear timing design ensures predictable pulse width derivation directly from external components.

Each monostable supports immediate termination via nCD, retriggering during an active output pulse to extend duration, and operates with TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max at VCC = 5.0 V) while maintaining CMOS power efficiency and latch-up immunity exceeding 100 mA per JESD78 Class II Level B.

Key Specifications

Pinout & Package

74HCT4538N,112 uses a 16-lead plastic dual in-line package (DIP), body width 7.62 mm, 2.54 mm lead pitch, through-hole mounting. Pin 1 index marked by notch or dot; pin 1 is top-left when notch faces up.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar monostable multivibrator applications.

Compared with 74HC4538N,112 and SN74LS4538N, the 74HCT4538N,112 uniquely balances TTL input compatibility with CMOS power efficiency and ±0.2 % pulse width stability-making it optimal for new 5 V designs demanding precision, low heat, and robust noise immunity.

Availability

74HCT4538N,112 is available at Aetrix Electronics and suitable for industrial motor control, automotive sensor interface, data acquisition triggering, and test equipment pulse shaping requiring stable component supply and long-term production continuity.

Supply support for 74HCT4538N,112 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 focused on high-volume, high-reliability logic, analog, and MOSFET solutions for automotive, industrial, and consumer markets.

The 74HCT4538N,112 belongs to Nexperia's HCT logic family, engineered specifically for seamless integration between TTL and CMOS systems-delivering TTL-compatible inputs with CMOS power efficiency and precision timing performance.

FAQ

What is the recommended supply voltage range for the 74HCT4538N,112?

The 74HCT4538N,112 is specified for operation from 4.5 V to 5.5 V. Operation outside this range may cause timing inaccuracies or failure to meet propagation delay specifications. The device is not rated for 3.3 V operation; for lower-voltage systems, consider the 74HC4538N,112 variant instead. Always use local 100 nF ceramic decoupling at the VCC pin.

How does the 74HCT4538N,112 calculate output pulse width?

The 74HCT4538N,112 calculates output pulse width as TW = 0.7 × REXT × CEXT, where REXT connects between nREXT/CEXT and VCC, and CEXT connects between nCEXT and GND. This linear relationship holds across the full operating temperature range (-40 °C to +125 °C) with ±0.2 % variation, enabling predictable, component-driven timing without software calibration.

Can the 74HCT4538N,112 be triggered by both rising and falling edges simultaneously?

No-the 74HCT4538N,112 assigns distinct edge sensitivity per input: nA triggers on HIGH-to-LOW transitions, and nB triggers on LOW-to-HIGH transitions. Both cannot initiate the same monostable simultaneously; however, either input can retrigger an active pulse. This separation enables deterministic edge selection in mixed-signal timing applications.

What is the function of the nCD pin on the 74HCT4538N,112?

The nCD pin on the 74HCT4538N,112 is an active-LOW direct reset input. When pulled LOW, it immediately terminates the current output pulse on its associated channel-regardless of ongoing retrigger activity or timing capacitor charge state. This provides deterministic pulse cancellation for safety-critical or fault-handling logic paths.

Is the 74HCT4538N,112 RoHS compliant and halogen-free?

Yes, the 74HCT4538N,112 is RoHS compliant and halogen-free per Nexperia's product compliance documentation (document ID: 74HCT4538 v.7, Rev. 7 - 26 March 2024). It meets EU Directive 2011/65/EU and IEC 61249-2-21:2018 requirements, with full material declarations available upon request from Aetrix Electronics or directly from Nexperia's compliance portal.