RTC-72421A

Real Time Clock Overview

The EPSON RTC-72421A is a 4-bit real-time clock module featuring a built-in crystal unit for adjustment-free operation. It supports both 24-hour and 12-hour formats with automatic Gregorian leap year adjustment. The device operates within a supply voltage range of 4.5 V to 5.5 V, consuming 10 µA typical current at 5 V. Frequency precision is ±10 × 10⁻⁶ at +25 °C. It utilizes a parallel interface with dedicated control signals including /CS0, ALE, /RD, and /WR.

Real Time Clock Feature Summary

• Built-in crystal unit eliminates external oscillator requirements
• Automatic leap year adjustment for Gregorian calendar
• Configurable 24-hour or 12-hour time format
• Low power consumption: 10 µA typical at VDD = 5 V

Real Time Clock Applications

• Car multimedia systems
• Body electronics
• Remote keyless entry systems

Real Time Clock Procurement Notes

Verify the specific suffix 'A' indicates the ±10 ppm frequency precision variant. Confirm package type matches DIP-18 requirements. Check RoHS compliance status as exemptions may apply for certain materials. Ensure operating temperature range (-10 °C to +70 °C) aligns with system constraints.

Real Time Clock Selection Notes

Select the RTC-72421A over the B variant when tighter frequency stability (±10 ppm vs ±50 ppm) is required. Note that this series lacks complete compatibility with the older RTC-6242 series; consult technical manuals before replacing legacy components. Verify voltage levels match the 4.5 V to 5.5 V specification.

Real Time Clock Part Context

This component belongs to the Epson RTC-7242 series, which includes the SOP-24 packaged RTC-72423 variants. The RTC-72421A specifically denotes the DIP-18 package version with high-frequency precision. It serves as a direct replacement for general-purpose timing applications requiring integrated crystal solutions.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. Caution is advised when replacing the older RTC-6242 series, as the 7242 series does not guarantee complete compatibility.