DS1340U-33+T&R

Real Time Clock Overview

The DS1340U-33+T&R is a low-power real-time clock (RTC) and calendar manufactured by Analog Devices Inc./Maxim Integrated. It operates on an I2C bidirectional serial bus with a maximum clock frequency of 400kHz. The device provides timekeeping for seconds, minutes, hours, day, date, month, and year in BCD format, including automatic leap-year correction. It features a built-in power-fail detect circuit that switches to a backup supply when VCC drops below the power-fail voltage (VPF). The unit supports a trickle charger for secondary power sources and includes an oscillator stop flag. It is housed in an 8-pin µSOP package.

Real Time Clock Feature Summary

• I2C Interface: Supports standard mode (100kHz) and fast mode (400kHz) communication via SDA and SCL pins.
• Trickle Charger: Configurable charging capability on the VBACKUP pin using selectable resistors (250Ω, 2kΩ, 4kΩ) and diode options.
• Power Management: Automatic switching between primary (VCC) and backup (VBACKUP) supplies upon power failure detection.
• Oscillator Stop Flag (OSF): Indicates if the oscillator has stopped due to power loss or insufficient voltage.

Real Time Clock Applications

• Portable Instruments
• Point-of-Sale Equipment
• Medical Equipment
• Telecommunications

Real Time Clock Procurement Notes

Verify the specific suffix '+T&R' corresponds to the tape-and-reel packaging configuration required for automated assembly. Confirm the '33' designation matches the system's 3.3V nominal supply requirements. Ensure the 8-pin µSOP footprint aligns with the PCB layout specifications.

Real Time Clock Selection Notes

Select this component for applications requiring precise timekeeping with battery backup capabilities. The 3.3V variant is suitable for systems operating within the 2.97V to 5.5V range. Consider the integrated trickle charger if maintaining a supercapacitor or rechargeable backup source is necessary. Verify compatibility with the host microcontroller's I2C voltage levels.

Real Time Clock Part Context

This part belongs to the DS1340 family of RTCs, which are functionally equivalent to the ST M41T00. The 'U' suffix denotes the 8-pin µSOP package, while 'Z' indicates the SOIC package. The '+T&R' suffix specifies lead-free/RoHS compliance and tape-and-reel packaging. Other variants include DS1340U-18+ and DS1340U-3+ for different voltage ranges.

Real Time Clock Replacement Considerations

The DS1340 is pin-compatible and functionally equivalent to the ST M41T00. When replacing, ensure the substitute supports the same I2C interface and voltage range. Verify that the replacement device offers similar trickle-charge functionality if battery maintenance is required.