NJU6355EM

Real Time Clock Overview

The NJU6355EM is a serial I/O real-time clock designed for 4-bit microprocessors, manufactured by Nisshinbo Micro Devices Inc. It integrates a quartz crystal oscillator, counter, shift register, voltage regulator, and low battery detector within a single CMOS chip. The device supports an operating voltage range of 2.0V to 5.5V, ensuring accurate timekeeping during backup periods with typical current consumption below 3µA at 2.0V. It utilizes a 4-port interface (DATA, CLK, CE, I/O) for data transfer and provides automatic leap year compensation up to AD 2099.

Real Time Clock Feature Summary

• Low operating voltage range from 2.0V to 3.6V with typical current consumption of 3.0µA at 2.0V and 4.0µA at 5.0V.
• BCD counting for seconds, minutes, hours, days of week, day, month, and year with automatic leap year compensation up to AD 2099.
• Integrated low battery detector outputs a warning signal when supply voltage drops below the detection level.
• Requires only four microprocessor ports (DATA, CLK, CE, I/O) for serial data transfer.

Real Time Clock Applications

• Embedded systems requiring precise timekeeping with minimal power consumption.
• Battery-operated devices utilizing backup power supplies.
• Microprocessor-based control units needing calendar and timer functions.

Real Time Clock Procurement Notes

Verify the specific package variant, as the NJU6355 series includes DIP8 and DMP8 options. Confirm that the application circuit adheres to the absolute maximum ratings, particularly regarding supply voltage limits and input voltage constraints relative to VDD. Ensure proper handling of the low battery detection logic in the host system design.

Real Time Clock Selection Notes

Select the NJU6355EM for applications requiring a compact serial RTC with wide voltage compatibility. The internal oscillation capacitors are specified as Cd=21pF and Cg=21pF, eliminating the need for external components for the 32.768kHz crystal. Consider the 4-port interface requirement when designing the microprocessor connection.

Real Time Clock Part Context

The NJU6355EM belongs to the NJU6355 series of serial I/O real-time clocks. Other variants in this series include the NJU6355ED, which shares similar functional characteristics but may differ in packaging or specific electrical parameters defined by the manufacturer's lineup table.

Real Time Clock Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. Evaluate alternatives based on compatible serial interfaces, voltage ranges, and package types if direct replacement is required.

Real Time Clock FAQ

What is the internal capacitance value for the connected quartz crystal?

The internal oscillation capacitors are Cd=21pF and Cg=21pF.

How does the device indicate a low battery condition?

When the supply voltage reduces to the detection level, the code (EE)H is written into each digit of the timer data and read out as a warning.

What is the maximum year supported for automatic leap year calculation?

The device provides automatic leap year compensation up to AD 2099.