Nexperia USA Inc. 74HCT4538D-Q100,11

Overview

74HCT4538D-Q100 from Nexperia is a dual retriggerable-resettable precision monostable multivibrator in SO16 package, designed for automotive timing control with ±0.2% pulse width variation over temperature, 0.7 × R_EXT × C_EXT output pulse width formula, and independent rising/falling-edge triggering per channel. It operates from 4.5 V to 5.5 V across –40 °C to +125 °C and features Schmitt-trigger inputs, active-low direct reset (nCD), and complementary outputs (nQ/nQ) - used in engine control unit (ECU) pulse shaping and anti-glitch signal conditioning.

For engineers reviewing the 74HCT4538D-Q100 datasheet, 74HCT4538D-Q100 pinout, 74HCT4538D-Q100 application, or 74HCT4538D-Q100 equivalent, key selection criteria include external timing component dependency (REXT/CEXT), dual-channel retriggerability, AEC-Q100 Grade 1 qualification, propagation delay ≤90 ns at 4.5 V, and tolerance to slow input edges - all critical for deterministic timing in safety-relevant automotive subsystems.

Technical Context

This device implements two independent monostable circuits, each with dual trigger inputs (nA for falling-edge, nB for rising-edge), a dedicated active-low reset (nCD), and complementary outputs (nQ high-active, nQ low-active). Pulse width is externally set via resistor-capacitor networks connected to nREXT/CEXT and nCEXT pins, with linear design ensuring precise 0.7 × R_EXT × C_EXT timing accuracy.

Schmitt-trigger action on nA/nB inputs enables robust operation with slow-rising/falling signals up to 139 ns/V, while clamp diodes allow interface to voltages exceeding V_CC using current-limiting resistors. The circuit supports retriggering during an active output pulse, enabling pulse extension without requiring full timeout completion.

Key Specifications

Pinout & Package

74HCT4538D-Q100 uses the SO16 (SOT109-1) plastic small outline package: 16-pin, 3.9 mm body width, 1.27 mm lead pitch, gull-wing leads, JEDEC MS-012 compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HCT4538PW-Q100, the D-package offers superior thermal resistance and legacy footprint compatibility; versus SN74LV4538A-Q1, it delivers tighter pulse accuracy and certified AEC-Q100 compliance - making it the preferred choice for safety-critical timing functions in powertrain ECUs.

Availability

74HCT4538D-Q100 is available at Aetrix Electronics and suitable for engine control units, transmission control modules, and ABS electronic control units requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 74HCT4538D-Q100 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 MOSFET solutions, with leadership in automotive-qualified components and advanced packaging.

The 74HCT4538-Q100 belongs to Nexperia's automotive-qualified HCT logic family, engineered specifically for deterministic timing in harsh-environment control systems where precision, noise immunity, and AEC-Q100 compliance are mandatory.

FAQ

What external components are required for basic operation?

The 74HCT4538D-Q100 requires two external timing components per channel: a resistor (R_EXT) between nREXT/CEXT and V_CC, and a capacitor (C_EXT) between nCEXT and GND. Typical values range from 2 kΩ to 1 MΩ for R_EXT and 100 pF to 1 μF for C_EXT, yielding pulse widths from ~140 ns to ~700 ms. No pull-up/down resistors are needed on trigger or reset inputs due to internal Schmitt triggers and defined logic thresholds.

How does retriggering affect the output pulse width?

When a new trigger occurs during an active output pulse, the monostable restarts its timing cycle from the retrigger event - extending the total pulse width by the full R_EXT × C_EXT-determined interval. This behavior is confirmed in the function table and timing diagram (Fig. 5), where retriggering (labeled "pulse lengthening") resets the internal timer without requiring the prior pulse to expire.

Can the 74HCT4538D-Q100 drive standard 5 V TTL loads directly?

Yes - the 74HCT4538D-Q100 provides TTL-compatible output levels: VOH ≥ 3.7 V at IO = –4.0 mA and VOL ≤ 0.4 V at IO = 4.0 mA under recommended operating conditions (V_CC = 4.5 V). Its 4 mA drive strength meets standard TTL fan-out requirements (one 74LS gate ≈ 0.4 mA input), supporting direct interface to legacy automotive logic without level-shifting buffers.

Is power-down protection necessary when using large C_EXT values?

Yes - if C_EXT exceeds ~100 nF, energy stored in the capacitor during normal operation can discharge through input protection diodes during rapid V_CC collapse, risking latch-up or junction damage. Nexperia recommends adding a germanium or Schottky damping diode (DEXT) between nREXT/CEXT and GND, as shown in Figure 10, to safely bleed stored charge during power-down sequences.