Nexperia USA Inc. HEF4538BT,653

Overview

HEF4538BT,653 from Nexperia is a dual retriggerable-resettable monostable multivibrator in SO16 package, operating from 3 V to 15 V supply, delivering precise output pulse widths (t_W = R_EXT × C_EXT) with ±0.2 % temperature stability and edge-triggered operation on both nA (HIGH-to-LOW) and nB (LOW-to-HIGH) inputs. It features active-low direct reset (nCD), complementary outputs (nQ/nQ), and Schmitt-trigger inputs for noise immunity-used in timing control, pulse shaping, and debounce circuits in industrial control systems.

For engineers reviewing the HEF4538BT,653 datasheet, HEF4538BT,653 pinout, HEF4538BT,653 application, or HEF4538BT,653 equivalent, key selection considerations include its dual-monostable architecture, external R/C timing flexibility (10 μs to ∞), wide V_DD range, −40 °C to +125 °C operation, and SO16 package compatibility with legacy 4000-series logic layouts.

Technical Context

The HEF4538BT,653 implements two independent LOCMOS-based monostables, each with dual-edge trigger capability (nA negative-edge, nB positive-edge), overriding active-low reset (nCD), and linear timing governed by external R_EXT/C_EXT. Pulse width accuracy is maintained via local oxide CMOS process, minimizing drift across voltage (±1.5 % over 5–15 V) and temperature (±0.2 % over −40 °C to +125 °C).

Each monostable provides true/complement outputs (nQ/nQ) with symmetrical drive (±2.4 mA at 15 V), propagation delays as low as 32 ns (15 V), and input hysteresis enabling tolerance of slow-rising signals. Unused inputs require tie-off to V_DD, V_SS, or another input-no internal pull-ups/pull-downs.

Key Specifications

Pinout & Package

HEF4538BT,653 is housed in a plastic small outline package (SO16), SOT109-1, with 16 leads, 3.9 mm body width, and standard 1.27 mm lead pitch-compatible with automated PCB assembly and legacy 4000-series footprints.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD4538BE and 74HC4538D, the HEF4538BT,653 uniquely combines −40 °C to +125 °C operation, ±0.2 % timing accuracy, and 3–15 V supply flexibility-making it the only option for high-stability timing in uncontrolled thermal environments without voltage regulation.

Availability

HEF4538BT,653 is available at Aetrix Electronics and suitable for industrial timer modules, microcontroller input debounce circuits, legacy system timing upgrades, and test equipment pulse generators requiring stable component supply across extended temperature ranges and mixed-voltage designs.

Supply support for HEF4538BT,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 focused on essential efficiency technologies, delivering high-performance logic, analog, and MOSFET solutions for automotive, industrial, and consumer markets.

The HEF4538BT,653 belongs to Nexperia's precision timing logic family, designed specifically for applications demanding stable, retriggerable monostable behavior across wide voltage and temperature ranges-targeting industrial control, instrumentation, and legacy system modernization.

FAQ

What is the minimum external timing capacitor value supported?

The datasheet specifies C_EXT ≥ 2000 pF for guaranteed accuracy. Using smaller values increases susceptibility to leakage current errors and reduces pulse width stability. For 10 μs minimum pulse width, typical design uses C_EXT = 2 nF with R_EXT = 5 kΩ at 5 V-verified in Table 8 timing data.

Can unused inputs be left floating?

No. All unused inputs-including nA, nB, nCD, and nREXT/CEXT-must be tied to V_DD, V_SS, or another driven input. Floating inputs cause increased supply current, erratic triggering, and potential latch-up due to CMOS input stage instability, as explicitly stated in Section 1 General Description.

How does the retrigger function interact with an active output pulse?

A retrigger event (nA↓ or nB↑) during an active output pulse extends the total pulse width by one additional t_W period-effectively restarting the monostable timer. This behavior is confirmed in Fig. 3 timing diagram (label "(2) Positive edge re-triggering (pulse lengthening)") and functional table entry for nA↓ with nCD = H.

Is the HEF4538BT,653 automotive-qualified?

No. Per Nexperia's legal disclaimers (Section 14), this device is explicitly labeled "Non-automotive qualified" and has not undergone AEC-Q100 stress testing. Its −40 °C to +125 °C rating applies to industrial use only; automotive applications require devices formally certified to AEC-Q100 Grade 1 or 2 standards.