DS12885QN+

Overview

The DS12885QN+ is a real-time clock and calendar integrated circuit manufactured by Analog Devices Inc./Maxim Integrated. It provides timekeeping for seconds, minutes, hours, day, date, month, and year with automatic leap year compensation through 2099. The device includes 114 bytes of battery-backed static RAM and supports both Intel and Motorola bus timing modes via a multiplexed parallel interface. It operates within a supply voltage range of 4.5V to 5.5V and features an industrial temperature rating from -40°C to +85°C. The component is housed in a 28-PLCC surface-mount package.

Feature Summary

• Multiplexed byte-wide parallel interface supporting Intel and Motorola bus timing modes
• 114 bytes of nonvolatile, battery-backed static RAM (NVSRAM)
• Automatic date adjustment for varying month lengths and leap years through 2099
• Programmable square-wave output and time-of-day alarm with maskable interrupts

Applications

• Embedded systems requiring precise timekeeping
• Utility meters for data logging and timestamping
• Security systems needing event recording
• Network hubs, bridges, and routers for synchronization

Procurement Notes

Verify the specific suffix 'QN+' against the manufacturer's current product status documentation. Suffixes often indicate packaging variations or environmental compliance levels such as RoHS. Confirm that the industrial temperature grade (-40°C to +85°C) matches the application requirements, as commercial variants exist with different thermal limits.

Selection Notes

Select this component when a parallel interface is required for direct CPU connection without software overhead associated with serial protocols. Ensure the system design accommodates the external 32.768kHz crystal oscillator connected to pins X1 and X2. Verify that the primary power supply remains stable between 4.5V and 5.5V and that a backup battery source is available for the VBAT pin during power failures.

Part Context

The DS12885 family serves as a drop-in replacement for legacy IBM AT computer clock/calendar chips like the DS1285 and DS1287. The 'QN' designation specifically identifies the industrial temperature range variant packaged in a 28-pin Plastic Leadless Chip Carrier (PLCC). This model integrates the RTC logic and NVSRAM into a single surface-mount solution suitable for dense PCB layouts.

Replacement Considerations

The DS12885T is listed as a direct replacement option, offering identical functionality in a 32-TQFP package. Designers must account for the pinout differences and footprint changes when transitioning from the 28-PLCC to the 32-TQFP form factor.