DS1342U+

Real Time Clock Overview

The DS1342U+ is a low-current real-time clock (RTC) from Analog Devices/Maxim Integrated, housed in an 8-pin µSOP package. It operates within a voltage range of +1.8V to +5.5V and maintains time down to +1.15V with a typical standby current of 250nA. The device supports high-ESR crystals up to 100kΩ and is optimized for crystals with a load capacitance (CL) of 12.5pF. It features a fast 400kHz I2C interface, two time-of-day alarms, interrupt outputs, and a programmable square-wave output. The clock/calendar includes leap year compensation valid through 2099 and supports external clock synchronization.

Real Time Clock Feature Summary

• Low timekeeping current of 250nA (typical) at +3.0V
• Compatible with crystal ESR up to 100kΩ and CL = 12.5pF
• Fast-mode I2C interface (400kHz) with bus timeout mechanism
• Two time-of-day alarms with interrupt outputs and programmable square wave

Real Time Clock Applications

• Medical devices
• Point of Sale (POS) systems
• Telematics units
• Portable instruments
• Portable audio equipment

Real Time Clock Procurement Notes

Verify the specific ordering suffix matches the required packaging format. The base part number DS1342U+ denotes the 8-pin µSOP package. Suffixes such as T&R indicate tape and reel packaging. Confirm RoHS compliance and lead-free status as indicated by the '+' designation in the manufacturer's documentation.

Real Time Clock Selection Notes

Select the DS1342U+ over the DS1341 variant when the application requires compatibility with crystals having a 12.5pF load capacitance. Ensure the system design accommodates the -40°C to +85°C industrial temperature range. Verify that the I2C bus pull-up resistors are correctly sized for the open-drain SDA and CLKIN/INTA pins.

Real Time Clock Part Context

The DS1342U+ belongs to the DS1341/DS1342 family of low-current RTCs. It shares functional similarities with the DS1341 but differs in oscillator loading requirements. The DS1342 is specifically tuned for 12.5pF crystals, whereas the DS1341 uses 6pF crystals. Both devices offer identical interface and alarm features.

Real Time Clock Replacement Considerations

The DS1341U+ is a direct functional substitute if the crystal load capacitance requirement can be adjusted to 6pF. Other Maxim Integrated RTCs with I2C interfaces may serve as alternatives, provided pin compatibility and register maps are verified.

Real Time Clock FAQ

What is the maximum crystal ESR supported by the DS1342U+?

The DS1342U+ supports crystals with a series resistance (ESR) of up to 100kΩ.

How does the DS1342U+ handle external clock synchronization?

It accepts an external clock reference on the CLKIN pin. When enabled, the RTC locks to this source if the frequency is within ±0.8% of the internal oscillator; otherwise, it reverts to the crystal oscillator.

What is the minimum voltage required to maintain timekeeping?

Timekeeping is maintained down to a typical voltage of +1.15V, with operation guaranteed down to +1.3V.