NXP Semiconductors 74HCT5555N,112

Overview

74HCT5555N,112 from Nexperia is a high-speed CMOS programmable delay timer with integrated oscillator, functioning as a precision digital timing controller in motor control, appliance timers, and automotive delay circuits. It features retriggerable/non-retriggerable operation, 24-stage binary counter, RC/crystal/external clock support, and minimum 100 ns output pulse width at VCC = 4.5 V.

For engineers reviewing the 74HCT5555N,112 datasheet, 74HCT5555N,112 pinout, 74HCT5555N,112 application, or 74HCT5555N,112 equivalent, key selection criteria include oscillator mode selection (OSC CON), division ratio programming (S0–S3), edge-triggering flexibility (A/B inputs), master reset behavior (MR), and HCT-level TTL-compatible input thresholds.

Technical Context

The 74HCT5555N,112 implements a digitally programmable monostable using a 24-stage synchronous binary counter driven by an external or internal oscillator. Its timing resolution is determined by the selected division ratio (2¹ to 2²⁴) and oscillator frequency (1 Hz–4 MHz for RC; 32 kHz–20 MHz for crystal).

It supports three oscillator configurations: RC network (RTC/CTC pins), parallel-resonant crystal (RTC/CTC + R₂/C₂), or direct external clock applied to RS. The OSC CON pin selects between continuously running (OSC CON = HIGH) or triggered-start (OSC CON = LOW) oscillator modes, enabling ultra-low quiescent power in standby.

Key Specifications

Pinout & Package

74HCT5555N,112 is housed in a 16-pin plastic DIL package (SOT38Z), compliant with JEDEC MS-001, with 2.54 mm pitch and through-hole mounting.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC5555N,112 and CD74HC5555E, the 74HCT5555N,112 uniquely bridges TTL logic families while maintaining full functional equivalence-making it optimal for legacy system upgrades where input level compatibility is mandatory.

Availability

74HCT5555N,112 is available at Aetrix Electronics and suitable for motor control, domestic appliance timers, and automotive delay circuits requiring stable component supply across long production lifecycles.

Supply support for 74HCT5555N,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 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 74HCT5555N,112 belongs to Nexperia's 74HCT logic family-designed specifically for seamless interface between TTL and CMOS systems while delivering low power consumption and high noise immunity in timing-critical applications.

FAQ

What oscillator configurations does the 74HCT5555N,112 support?

The 74HCT5555N,112 supports three oscillator configurations: RC network (using RTC and CTC pins), parallel-resonant crystal (with external R₂ and C₂), or direct external clock applied to the RS pin. The OSC CON pin selects between continuous or triggered-start operation. All modes are fully supported in the 74HCT5555N,112 datasheet with validated frequency ranges and component guidelines.

How does the 74HCT5555N,112 achieve retriggerable vs. non-retriggerable operation?

The 74HCT5555N,112 uses the RTR/RTR pin (pin 6) to select mode: HIGH enables retriggering (output pulse extends on each new A or B trigger), while LOW locks the output duration after first trigger. This behavior is implemented in hardware with no software overhead, and is explicitly confirmed in the 74HCT5555N,112 functional description and timing diagrams.

What is the minimum programmable delay of the 74HCT5555N,112 and how is it achieved?

The 74HCT5555N,112 achieves a minimum output pulse width of 100 ns, specified at VCC = 4.5 V. This occurs when the 24-stage counter is configured for the shortest division ratio (2¹ = 2) and driven by the highest allowable oscillator frequency (up to 4 MHz in RC mode). The value is guaranteed in the AC characteristics table and verified across temperature and voltage ranges.

Is the 74HCT5555N,112 pin-compatible with other members of the 74HC/HCT5555 family?

Yes, the 74HCT5555N,112 is fully pin-compatible with all variants in the 74HC/HCT5555 family-including 74HC5555N,112 and 74HCT5555D-sharing identical pin configuration, function mapping, and package outline (SOT38Z for DIL). This allows direct substitution where electrical specifications align, as confirmed in the Philips/Nexperia ordering information and pinning diagrams.

Does the 74HCT5555N,112 include built-in power-on reset functionality?

Yes, the 74HCT5555N,112 integrates automatic power-on reset circuitry that initializes all internal flip-flops to a known state at power-up. This eliminates the need for external RC reset networks and is documented in the General Description and Functional Diagram sections of the 74HCT5555N,112 datasheet.