RS5C372A-E2-F

Real Time Clock Overview

The RS5C372A-E2-F is a CMOS real-time clock IC featuring an I2C bus serial interface. It operates within a supply voltage range of 1.7 V to 6.0 V, with a timekeeping voltage down to 1.3 V. Standby current consumption is typically 0.5 µA at 3 V and 25°C. The device includes BCD-coded counters for seconds, minutes, hours, day of the week, date, month, and year, supporting automatic leap year recognition until 2099. It offers two alarm systems, periodic interrupts, and a high-precision time trimming circuit. The component is housed in an 8-pin SSOP package.

Real Time Clock Feature Summary

• I2C bus interface supporting standard mode (up to 100 kHz) and fast mode (up to 400 kHz).
• Low standby current of 0.5 µA typical at 3 V, 25°C.
• Integrated high-precision time trimming circuit correcting frequency errors up to ±189 ppm.
• Dual alarm systems (Alarm_A, Alarm_B) with selectable interrupt outputs on INTRA and INTRB pins.

Real Time Clock Applications

• Communication devices such as multi-function phones, portable phones, PHS, or pagers.
• Office automation equipment including fax machines and portable faxes.
• Computers like desktops, mobile PCs, PDAs, and electronic notebooks.
• Audio/visual components including digital cameras, video cameras, and remote controllers.
• Home appliances such as rice cookers and electric ovens.

Real Time Clock Procurement Notes

Verify that the specific ordering suffix E2 corresponds to the taping type and F indicates lead-free plating as defined in the manufacturer's selection guide. Confirm compatibility with the host system's I2C voltage levels, noting that SCL and SDA inputs can tolerate up to 6 V beyond VDD. Ensure the design accounts for the open-drain nature of the SDA, INTRA, and INTRB pins, requiring appropriate pull-up resistors for proper signal integrity.

Real Time Clock Selection Notes

Select the RS5C372A-E2-F when dual independent alarm outputs are required, distinguishing it from the RS5C372B which shares a single interrupt pin. The device supports both 32.768 kHz and 32.000 kHz external crystals. Designers must implement software correction for the century digit, as the internal counter only tracks the lower two digits of the year. The time trimming function allows adjustment of clock accuracy based on temperature or crystal tolerance, reducing reliance on high-precision external oscillators.

Real Time Clock Part Context

The RS5C372A is part of the RS5C372 series manufactured by Nisshinbo Micro Devices, formed from the integration of New Japan Radio and Ricoh Electronics Devices. This series provides CMOS real-time clock solutions optimized for low power consumption and small form factors. The RS5C372A variant specifically features separate interrupt lines for alarms and periodic signals, facilitating complex scheduling tasks in embedded systems without pin contention.

Real Time Clock Replacement Considerations

The RS5C372B serves as a functional alternative within the same family but utilizes a single INTR pin for all interrupts and a dedicated 32KOUT pin for clock output. Pin compatibility differs; the RS5C372A uses INTRA/INTRB while the RS5C372B uses INTR/32KOUT. Software modifications are required to map interrupt handlers correctly if substituting between these variants.