R2221T-E2-F

Real Time Clock Overview

The R2221T-E2-F is a CMOS real-time clock IC manufactured by Nisshinbo Micro Devices, housed in a TSSOP-10 package. It interfaces with CPUs via a two-wire serial bus (SCL/SDA) supporting I2C fast mode up to 400 kHz. The device provides timekeeping and calendar functions in BCD format, including automatic leap year recognition through 2099. Key electrical parameters include a minimum timekeeping voltage of 0.6 V typ (0.9 V worst case) and ultra-low power consumption of 0.18 µA typ at 3 V in ECO mode. It features dual alarm circuits, selectable periodic interrupts, and a 32.768 kHz clock output.

Real Time Clock Feature Summary

• Ultra-low power consumption: 0.18 µA typ at VDD=3V in ECO mode; 0.35 µA typ without ECO mode.
• Dual alarm interrupt circuits: Alarm_W supports week/hour/minute settings; Alarm_D supports hour/minute settings.
• High-precision oscillation adjustment: Built-in capacitors allow correction of frequency deviations up to ±189 ppm.
• Comprehensive status monitoring: Includes power-on reset flag, oscillation halt sensing, and supply voltage monitoring.

Real Time Clock Applications

• Portable electronic devices requiring precise timekeeping with minimal battery drain.
• Systems utilizing external microcomputers needing a sub-clock pulse output.
• Battery-operated equipment where supply voltage monitoring is critical for data integrity.

Real Time Clock Procurement Notes

Verify the specific suffix 'E2-F' corresponds to the TSSOP-10G package and lead-free composition as listed in the selection guide. Confirm that the ECO mode functionality aligns with the hardware pin configuration, as this variant utilizes an external ECO pin rather than internal register control alone. Ensure pull-up resistors are present on SDA/SCL lines if interfacing with CPUs having different supply voltages.

Real Time Clock Selection Notes

Select the R2221T-E2-F when a TSSOP-10 surface-mount package is required. Note that this model uses an external ECO pin for oscillator mode selection, unlike the R2223x series which controls this via registers. Choose this part over the R2221L-E2 if board space accommodates the larger TSSOP footprint but requires the specific pinout for the ECO control signal.

Real Time Clock Part Context

This component belongs to the R2221x/R2223x family of 2-wire serial interface real-time clocks. The R2221T-E2-F specifically denotes the TSSOP-10G package variant. It shares core functionalities with the R2223x series but differs in interrupt pin architecture (single INTR vs. dual INTRA/INTRB) and ECO mode activation method (pin vs. register).

Real Time Clock Replacement Considerations

The R2223T-E2-F is a functional alternative within the same package but offers dual interrupt pins (INTRA/INTRB) and register-controlled ECO mode instead of a dedicated ECO pin. Pin compatibility exists for VDD, VSS, SCL, SDA, OSCIN, OSCOUT, CLKC, and 32KOUT, but INTR and ECO pin mappings differ.