Nexperia USA Inc. 74HCT4538PW,112

Overview

74HCT4538PW,112 from Nexperia is a dual retriggerable-resettable precision monostable multivibrator in TSSOP16 package, operating from 4.5 V to 5.5 V over -40 °C to +125 °C. Each channel provides independent rising- and falling-edge triggering (nA/nB), active-low direct reset (nCD), complementary outputs (nQ/nQ), and external timing via REXT/CEXT. Output pulse width is precisely 0.7 × REXT × CEXT with ±0.2 % typical variation over temperature - used in industrial timing control, pulse shaping, and debounce circuits.

For engineers reviewing the 74HCT4538PW,112 datasheet, 74HCT4538PW,112 pinout, 74HCT4538PW,112 application, or 74HCT4538PW,112 equivalent, key selection criteria include edge-trigger flexibility, Schmitt-trigger input tolerance for slow signals, TTL-compatible inputs, guaranteed propagation delay ≤90 ns at 4.5 V, and dual-channel independence for synchronized or isolated timing functions.

Technical Context

The device implements two independent monostable circuits using CMOS logic with Schmitt-trigger inputs, enabling reliable triggering on both rising and falling edges without external conditioning. Each channel features separate nCD reset, dual trigger inputs (nA for negative-edge, nB for positive-edge), and complementary outputs with defined timing relationships.

Timing accuracy relies on external REXT and CEXT components connected to dedicated pins (nREXT/CEXT and nCEXT); pulse width is linearly proportional to their product (TW = 0.7 × REXT × CEXT) and exhibits minimal drift across voltage (±0.2 %), temperature, and component tolerances - confirmed by characterization up to ±10 % REXT and >100 nF CEXT.

Key Specifications

Pinout & Package

TSSOP16 plastic thin shrink small outline package (SOT403-1), 16 leads, body width 4.4 mm, lead pitch 0.65 mm - optimized for high-density PCB layouts and automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC4538PW,118, the 74HCT4538PW,112 offers superior noise immunity and guaranteed TTL input compatibility at the cost of slightly higher quiescent current; versus SN74LS422N, it delivers retriggerability, ±0.2 % timing accuracy, and extended temperature support - critical for modern industrial timing integrity.

Availability

74HCT4538PW,112 is available at Aetrix Electronics and suitable for industrial motor control, automated test equipment, medical instrumentation, and industrial sensor interface applications requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 74HCT4538PW,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, discrete, and power devices - delivering robust, automotive-qualified and industrial-grade components with stringent quality control.

The 74HCT4538 belongs to Nexperia's high-speed CMOS logic family designed specifically for precision timing applications demanding edge-selective triggering, retriggerability, and exceptional thermal stability in harsh environments.

FAQ

What is the minimum recommended CEXT value for stable operation?

The datasheet does not specify a minimum CEXT value, but characterization data (Fig. 11–13) confirms stable operation down to 1 nF with REXT = 1 kΩ to 1 MΩ. For pulse widths below 1 μs, use CEXT ≥ 100 pF and verify timing accuracy against Fig. 13's ±10 % REXT tolerance curves at your target VCC and temperature.

Can 74HCT4538PW,112 operate with VCC = 3.3 V?

No - the device is specified only for 4.5 V to 5.5 V supply. At 3.3 V, VIH/VIL thresholds are violated (VIH min = 2.0 V at VCC ≥ 4.5 V), propagation delays exceed specification, and output drive falls outside guaranteed limits. Use 74LVC4538 for 3.3 V operation.

How does the retrigger function behave when nCD is held LOW?

When nCD is LOW, the output is forced LOW regardless of nA/nB activity - retriggering is fully inhibited. The monostable remains in reset state until nCD returns HIGH, after which the next valid edge on nA or nB initiates a new pulse. No pulse extension occurs during nCD assertion.

Is there a risk of latch-up when connecting large CEXT values?

Yes - large CEXT (>1 μF) stores significant energy; rapid VCC ramp-down can discharge through input protection diodes, risking latch-up or damage. Per Section 11.1, add a germanium or Schottky damping diode (DEXT) between nREXT/CEXT and GND to safely bleed stored charge during power-off sequences.