NXP Semiconductors 74HCT5555D,118

Overview

74HCT5555D,118 from Nexperia is a high-speed CMOS programmable delay timer with integrated oscillator, featuring 24-stage binary counter, retriggerable/non-retriggerable monostable operation, and dual active-HIGH/active-LOW outputs (Q/Q). It supports RC, crystal, or external clock inputs, delivers 20 mA output drive, and achieves minimum 100 ns delay with ±1% accuracy for delays ≥400 ns - used in precision motor control timing and attic fan delay circuits.

For engineers reviewing the 74HCT5555D,118 datasheet, 74HCT5555D,118 pinout, 74HCT5555D,118 application, or 74HCT5555D,118 equivalent, key selection criteria include oscillator mode selection (OSC CON), retriggerability control (RTR/RTR), programmable division ratio (S0–S3), propagation delays (A/B→Q: 28–48 ns), and compatibility with 4.5 V TTL-level MR input and CMOS-level RS input.

Technical Context

The 74HCT5555D,118 implements digital timing via a 24-stage binary counter programmed by S0–S3 inputs to select division ratios from 2¹ to 2²⁴ (2 to 16,777,216). Its oscillator circuit accepts RC networks (R_EXT = 1–1000 kΩ, C_EXT ≥ 50 pF), crystal (32 kHz–20 MHz), or external clock (up to 10 MHz at V_CC = 4.5 V).

Triggering supports positive-edge (input A), negative-edge (input B), or both; Schmitt-trigger inputs ensure noise immunity. The device features automatic power-on reset, asynchronous master reset (MR), and oscillator control (OSC CON) for triggered-start (low-power) or continuous-run modes - enabling precise, jitter-free pulse generation synchronized to the falling edge of the oscillator clock.

Key Specifications

Pinout & Package

74HCT5555D,118 is housed in a 16-pin SO16 (SOT109A) plastic surface-mount package, 10.0 mm × 4.0 mm body, 1.45 mm max height, 1.27 mm pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar programmable delay timer applications.

Compared with 74HC5555D,118 and CD4060BE, the 74HCT5555D,118 uniquely combines TTL-compatible MR input, CMOS RS input, retriggerable monostable action, and integrated oscillator - delivering full delay-timer functionality in a single SO16 package without external timing logic.

Availability

74HCT5555D,118 is available at Aetrix Electronics and suitable for motor control timing, attic fan delay circuits, and precision industrial delay circuits requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for 74HCT5555D,118 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 leader in discrete, logic, and PowerMOS semiconductors, spun off from NXP's Standard Products business in 2017 and focused on automotive, industrial, computing, and consumer markets.

The 74HCT5555D,118 belongs to Nexperia's 74HCT logic family - designed for TTL-compatible interfacing in industrial control, appliance, and automotive timing applications where robustness, precision, and long-term supply stability are essential.

FAQ

What oscillator configurations does the 74HCT5555D,118 support?

The 74HCT5555D,118 supports three oscillator configurations: RC network (using RTC and CTC pins with R_EXT = 1–1000 kΩ and C_EXT ≥ 50 pF), crystal (32 kHz–20 MHz), and external clock applied to the RS pin. OSC CON pin selects between continuous-run and triggered-start modes - the latter minimizing power in standby. All modes are fully supported in the 74HCT5555D,118 datasheet with validated timing formulas and component guidelines.

How does the retriggerable mode work on the 74HCT5555D,118?

When RTR/RTR is HIGH, the 74HCT5555D,118 enters retriggerable mode: each new trigger on input A (rising) or B (falling) extends the current output pulse by the programmed delay period. This allows dynamic pulse-length adjustment - e.g., keeping a motor running while motion is detected. In non-retriggerable mode (RTR/RTR = LOW), the 74HCT5555D,118 ignores subsequent triggers until the initial delay completes. Both behaviors are guaranteed per the 74HCT5555D,118 functional description.

What is the minimum achievable delay time for the 74HCT5555D,118?

The 74HCT5555D,118 guarantees a minimum output pulse width of 100 ns, verified across temperature (−40 to +85 °C) and supply (4.5 V). Accuracy is better than 1% for delays ≥400 ns, with deviation increasing for shorter pulses due to propagation delay asymmetry (A→Q vs. RS→Q). The 74HCT5555D,118 datasheet provides Fig.16 quantifying this error - up to 10% for 100 ns programmed width - making it unsuitable for sub-100 ns timing.

Can the 74HCT5555D,118 drive a power transistor directly?

Yes, the 74HCT5555D,118 can directly drive small power transistors: its Q and Q outputs deliver 20 mA sink/source capability at V_CC = 4.5 V, sufficient for gate drive of logic-level MOSFETs or base drive of medium-current BJTs. The 74HCT5555D,118 datasheet specifies VOL ≤ 0.4 V at I_O = 20 mA and VOH ≥ 3.3 V at I_O = −20 mA - confirming robust drive strength without external buffers in most low-power switching applications.

How does the 74HCT5555D,118 handle power-on initialization?

The 74HCT5555D,118 incorporates an internal automatic power-on reset circuit that forces all counter flip-flops to a known state (Q = LOW, Q = HIGH) at power-up, eliminating the need for external RC reset networks. This ensures deterministic startup behavior in systems where supply ramp rate varies - a feature explicitly documented in the 74HCT5555D,118 functional description and confirmed in the "Power-On Reset" section of its datasheet.