ISL12028IBAZ

Real Time Clock Overview

The ISL12028IBAZ is a low-power Real Time Clock (RTC) and calendar integrated circuit manufactured by Renesas Electronics. It features an I2C bus interface with a maximum data transfer rate of 400kHz. The device includes clock/calendar registers, two non-volatile alarms, and 512x8-bit EEPROM with page write mode. It operates on a main supply voltage (VDD) ranging from 2.7V to 5.5V and supports battery backup (VBAT) down to 1.8V. Key specifications include a typical battery supply current of 800nA at 1.8V VBAT, automatic leap year correction through 2099, and an operating temperature range of -40°C to +85°C.

Real Time Clock Feature Summary

• Integrated 512x8-bit EEPROM with BlockLock protection and >2,000,000 cycle endurance.
• Dual non-volatile alarms with periodic interrupt capability and hardware interrupt output.
• On-chip oscillator compensation with 64-position digitally controlled trim capacitors for frequency adjustment.
• CPU supervisor functions including Power-On Reset, Low Voltage Sense, and Watchdog Timer.

Real Time Clock Applications

• Utility meters
• HVAC equipment
• Network routers, hubs, switches, and bridges

Real Time Clock Procurement Notes

Verify the specific suffix 'BAZ' against official Renesas documentation, as standard listings typically utilize suffixes like 'IB27Z' or 'IVZ'. Confirm availability status, as many variants in this family are marked as obsolete or have limited supply. Ensure the selected package matches the required PCB footprint, as SOIC-14 and TSSOP-14 options exist within the series.

Real Time Clock Selection Notes

Select based on the required VRESET threshold and battery switching configuration. The ISL12028 uses Legacy Mode settings, whereas the ISL12028A variant uses Standard Mode. Applications where VBAT exceeds VDD may require the ISL12028A specifically. Verify that the I2C pull-up resistor values comply with the capacitive loading limits specified in the datasheet for reliable communication at 400kHz.

Real Time Clock Part Context

The ISL12028 belongs to the ISL12028/ISL12028A family of real-time clocks. It is designed to replace older RTC solutions by integrating oscillator compensation and EEPROM directly onto the chip, reducing external component count. The device is part of Renesas's portfolio for industrial and consumer applications requiring precise timekeeping with non-volatile memory storage.

Real Time Clock Replacement Considerations

The datasheet explicitly states this product is obsolete with no recommended replacement. Contact Technical Support for potential alternatives. Cross-model compatibility requires verifying power control settings (Legacy vs. Standard mode) and VRESET thresholds when considering ISL12028A variants.

Real Time Clock FAQ

What is the default battery switching behavior for the ISL12028?

The ISL12028 utilizes the Legacy Mode Setting for power control. The BSW bit defaults to 1, indicating specific battery switching logic distinct from the ISL12028A's Standard Mode.

How does the device handle time reading during active clock operation?

The RTC latches the time into a separate buffer upon the read command (falling edge of the clock on the ACK bit). This prevents time changes during the read operation, ensuring consistent data retrieval while the clock continues to run.

What is the function of the IRQ/FOUT pin?

The IRQ/FOUT pin serves a dual function. It can operate as an interrupt output to signal alarm events or as a frequency output providing selectable signals of 1Hz, 4096Hz, or 32,768Hz.