DS1558W+

Real Time Clock Overview

The DS1558W+ is a Y2K-compliant real-time clock (RTC) and watchdog timer with NV SRAM control, manufactured by Analog Devices Inc./Maxim Integrated. It operates at a nominal voltage of 3.3V (range 2.97V to 3.63V) and features a parallel interface within a 48-pin TQFP package (7x7x1mm). The device provides timekeeping for year, month, date, day, hours, minutes, and seconds in BCD format with automatic leap-year compensation valid through 2100. It includes an integrated watchdog timer, programmable alarm, power-fail write protection, and battery backup switching between VCC and VBAT inputs.

Real Time Clock Feature Summary

• Integrated RTC, watchdog timer, and NV SRAM controller with byte-wide parallel access
• BCD-coded calendar and clock registers with automatic leap-year correction valid to 2100
• Power-fail write protection and seamless battery switchover for data retention
• Programmable alarm and watchdog timer with interrupt output via IRQ/FT pin

Real Time Clock Applications

• Systems requiring Y2K-compliant timekeeping and data retention during power loss
• Embedded controllers needing watchdog timer functionality for system stability
• Industrial or commercial equipment operating in -40°C to +85°C environments

Real Time Clock Procurement Notes

Verify the specific ordering suffix (e.g., W+, W-TRL) to confirm packaging type (tray vs. reel) and lead-free status. Confirm that the 3.3V version matches the system supply voltage requirements. Ensure external pull-up resistors are included for open-drain outputs like RST and IRQ/FT as specified in the datasheet.

Real Time Clock Selection Notes

Select the DS1558W+ for 3.3V systems; use the DS1558Y+ variant for 5V applications. Both variants share the same pinout and functional specifications. Consider the TRL suffix if tape-and-reel packaging is required for automated assembly. Verify crystal load capacitance requirements (typically 6pF) for accurate oscillator performance.

Real Time Clock Part Context

The DS1558 series combines a real-time clock, watchdog timer, and NV SRAM controller into a single IC. The 'W' designation indicates the 3.3V operating voltage range, while 'Y' denotes the 5V version. The '+' suffix signifies RoHS compliance and lead-free construction. This component is part of Maxim's legacy RTC portfolio designed for robust timekeeping in microcontroller-based systems.

Real Time Clock Replacement Considerations

The DS1558Y+ serves as the direct 5V equivalent with identical pinout and functionality. For surface-mount alternatives with different packages, consult manufacturer cross-reference guides, but verify register compatibility and interface timing parameters carefully.