74HC5555N,112

Overview

The 74HC5555 is a precision programmable delay timer featuring a 24-stage binary counter, integrated oscillator, and retriggerable/non-retriggerable monostable circuitry. It operates on a supply voltage range of 2.0 V to 6.0 V with CMOS input levels. The device supports positive and negative edge triggering, Schmitt trigger inputs for noise immunity, and an overriding asynchronous master reset. It includes automatic power-ON reset and clamp diodes for input protection. The component provides high-precision digital timing with divide-by ranges from 2 to 2^24.

Feature Summary

• Programmable delay timer with 24-stage binary counter and divide-by range of 2 to 2^24
• Three oscillator modes: RC, crystal, or external clock input
• Retriggerable or non-retriggerable operation via RTR/RTR input
• Schmitt trigger action on trigger inputs A and B

Applications

• Motor control systems
• Precision timing circuits
• Delay circuits
• Domestic appliances

Procurement Notes

Verify the package type matches the required form factor; the 74HC5555N variant typically utilizes an SO16 (SOT109-1) plastic small outline package. Confirm the temperature grade aligns with system requirements, as the datasheet specifies operation from -40 °C to +125 °C. Ensure ordering suffixes correspond to the specific manufacturer versioning, such as Nexperia or NXP, as these may affect documentation but not electrical function.

Selection Notes

Select this component when precise digital delay generation is required without external microcontrollers. The choice between RC, crystal, or external oscillation depends on frequency stability needs. For applications requiring low power during standby, utilize the triggered start mode by setting OSC CON LOW. Ensure the external timing components (RT, CT) are selected within the recommended limits to maintain accuracy better than 1% for delays ≥ 400 ns.

Part Context

The 74HC5555 belongs to the 74HC/HCT series of high-speed Si-gate CMOS logic devices. It is pin-compatible with low-power Schottky TTL (LSTTL) standards. The device complies with JEDEC standard no. 7A and features ESD protection exceeding 2000 V (HBM). It serves as a direct replacement for older analog timer solutions in digital designs requiring programmable intervals.

Replacement Considerations

Public confirmed substitute part numbers include the 74HCT5555 for TTL-compatible logic levels. Other programmable delay timers like the LS7210 or LS7211 series offer similar functionality but may require interface adjustments.