Nexperia USA Inc. 74HCT123D,653

Overview

74HCT123D,653 from Nexperia is a dual retriggerable monostable multivibrator with independent reset inputs, TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max at VCC = 5 V), 16-pin SO16 package, −40 °C to +125 °C operating range, and programmable pulse width via external REXT/CEXT networks. It enables precise timing control in digital edge-detection and pulse-stretching circuits such as industrial sensor debouncing and serial data framing.

For engineers reviewing the 74HCT123D,653 datasheet, 74HCT123D,653 pinout, 74HCT123D,653 application, or 74HCT123D,653 equivalent, this device supports retriggerable one-shot operation with Schmitt-triggered A/B inputs, direct active-low reset per channel, and dual complementary outputs (nQ/nQ) - critical for noise-immune timing in mixed-signal embedded systems.

Technical Context

This IC implements two independent monostable multivibrators, each with separate negative-edge (nA) and positive-edge (nB) trigger inputs, dedicated reset (nRD), and dual outputs (nQ active LOW, nQ active HIGH). Pulse width tW is externally set by REXT and CEXT, with typical values ranging from 75 ns (REXT = 5 kΩ, CEXT = 0 pF) to 450 μs (REXT = 10 kΩ, CEXT = 100 nF) at VCC = 5 V.

Each monostable features Schmitt-trigger action on nA/nB inputs (Δt/ΔV = 139 ns/V at VCC = 4.5 V), enabling robust operation with slow-rising signals, while nRD accepts either LOW-going edges or sustained LOW for immediate output termination. Input clamping diodes allow interfacing to voltages exceeding VCC when used with current-limiting resistors.

Key Specifications

Pinout & Package

74HCT123D,653 uses the SOT109-1 plastic small outline package (SO16), 16-pin, 3.9 mm body width, with gull-wing leads and pin 1 index marker. Thermal resistance θJA = 110 K/W (JEDEC Std. 51-2).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC123D,653 and SN74LV123AD, the 74HCT123D,653 uniquely balances TTL compatibility, Schmitt-trigger robustness, and industrial temperature support - making it optimal for legacy 5 V systems requiring field reliability without redesign.

Availability

74HCT123D,653 is available at Aetrix Electronics and suitable for industrial motor control, automotive body electronics, and test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 74HCT123D,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 delivering high-performance, reliable discrete, logic, and MOSFET solutions with leadership in efficiency, miniaturization, and quality assurance.

The 74HCT123 series belongs to Nexperia's industry-standard logic portfolio, designed specifically for robust timing functions in automotive, industrial, and consumer applications where TTL compatibility and wide temperature operation are mandatory.

FAQ

What is the minimum external timing capacitor value supported?

The datasheet specifies CEXT down to 0 pF for basic timing operation, but recommends ≥10 pF for predictable pulse width behavior per Figure 5. At CEXT < 50 pF, a power-up reset pulse is required to avoid spurious output pulses. The inherent pin capacitance at nREXT/CEXT pins is approximately 7 pF, which contributes to total timing capacitance.

Can both channels be triggered simultaneously without interference?

Yes - the two monostables are electrically isolated except for shared VCC and GND rails. Simultaneous triggering of nA1/nB1 and nA2/nB2 produces independent output pulses with no crosstalk, verified by functional testing in Table 3 and dynamic characterization in Table 7.

How does the retrigger time (trtrig) depend on external components?

At VCC = 5.0 V, trtrig = 30 + 0.19 × REXT × CEXT^0.9 + 13 × REXT^1.05 (ns), where REXT is in kΩ and CEXT in pF. This formula ensures reliable retriggering only when successive trigger edges exceed this minimum interval - critical for avoiding missed extensions in long-pulse applications.

Is the 74HCT123D,653 pin-compatible with older 74LS123 variants?

No - while functionally similar, the 74HCT123D,653 uses a different pinout than 74LS123 (e.g., 74LS123 has separate R/C pins per channel; 74HCT123 shares REXT/CEXT nodes). Direct replacement requires PCB layout revision and verification of timing behavior due to differing propagation delays and input structures.