DS1342U+T&R

Real Time Clock Overview

The DS1342U+T&R 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 utilizes a 12.5pF load capacitance crystal. 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.

Real Time Clock Feature Summary

• Low standby current of 250nA (typical) at 3.0V
• Compatible with crystals having ESR up to 100kΩ
• Integrated capacitive loading for 12.5pF CL crystals
• Fast-mode I2C interface supporting 400kHz clock frequency

Real Time Clock Applications

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

Real Time Clock Procurement Notes

Verify the specific ordering suffix T&R indicates tape and reel packaging. Confirm the component is lead-free and RoHS-compliant as per the datasheet specifications. Ensure the supplier provides documentation confirming the 12.5pF crystal compatibility distinct from the DS1341 variant.

Real Time Clock Selection Notes

Select this model over the DS1341 when the application requires compatibility with 12.5pF load capacitance crystals rather than 6pF types. The DS1342 is suitable for designs needing support for higher equivalent series resistance (ESR) crystals up to 100kΩ. Verify that the system power supply remains above 1.8V during normal operation to ensure full I2C interface functionality.

Real Time Clock Part Context

This part belongs to the DS1341/DS1342 family of low-current I2C RTCs. The primary distinction between the DS1341 and DS1342 is the integrated capacitive loading: the DS1341 supports 6pF crystals, while the DS1342 supports 12.5pF crystals. Both share identical pinouts, interfaces, and feature sets regarding alarms and synchronization capabilities.

Real Time Clock Replacement Considerations

The DS1341U+T&R is a functional substitute if the circuit design accommodates 6pF crystals instead of 12.5pF. Other variants in the family include the TDFN package versions (DS1342T+). Ensure any replacement maintains the same 8-pin µSOP footprint or adapts accordingly.

Real Time Clock FAQ

What is the difference between DS1341 and DS1342?

The DS1342 uses a 12.5pF crystal load capacitance, whereas the DS1341 uses a 6pF crystal load capacitance. All other electrical characteristics and pinouts are identical.

Does the DS1342 require external resistors or capacitors for the oscillator?

No, the internal oscillator circuitry does not require external resistors or capacitors to operate, as it includes integrated capacitive loading for the specified crystal type.

How does the bus timeout mechanism work?

The bus timeout mechanism resets the serial bus interface if the SCL line is held low for a minimum duration (tTIMEOUT), preventing lockup-free operation issues.