DS1340Z-33/T&R

Real Time Clock Overview

The DS1340Z-33/T&R is a low-power real-time clock and calendar integrated circuit manufactured by Analog Devices Inc./Maxim Integrated. It operates with a primary supply voltage range of 2.97V to 5.5V and supports a backup supply from 1.3V to 5.5V. The device provides timekeeping for seconds, minutes, hours, day, date, month, and year in binary-coded decimal format. It features an I²C bidirectional serial interface supporting standard (100kHz) and fast (400kHz) modes. Key electrical characteristics include a maximum standby current of 150µA at 5.5V and a typical data-retention current of 100nA. The component is housed in an 8-pin SO package.

Real Time Clock Feature Summary

• I²C Interface: Supports standard mode (up to 100kHz) and fast mode (up to 400kHz) communication protocols.
• Trickle Charger: Includes programmable trickle-charge capability on the VBACKUP pin for charging backup batteries or supercapacitors.
• Automatic Power-Fail Detection: Built-in circuitry detects power failures and automatically switches between VCC and VBACKUP supplies without interrupting timekeeping.
• Software Clock Calibration: Allows compensation for crystal and temperature variations via digital calibration bits in the control register.

Real Time Clock Applications

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

Real Time Clock Procurement Notes

Verify the specific suffix 'T&R' indicates tape-and-reel packaging when sourcing components. Confirm that the 'Z' designation corresponds to the 8-pin SO package variant. Ensure compatibility with the required I²C bus voltage levels and pull-up resistor configurations as specified in the datasheet electrical characteristics.

Real Time Clock Selection Notes

Select this model for applications requiring a 3.3V nominal supply system with I²C connectivity. Consider the DS1340C variant if an integrated crystal is preferred over an external component. Evaluate the trickle charger settings against the specific backup power source requirements, noting that the 250Ω resistor option is restricted for VCC voltages exceeding 3.63V.

Real Time Clock Part Context

The DS1340 series serves as a pin-compatible and functionally equivalent alternative to the ST M41T00. The Z-33 suffix specifically identifies the version optimized for a 3.3V operating voltage range, packaged in an 8-pin Small Outline (SO) footprint. This part belongs to the broader family of Maxim Integrated RTCs designed for low-power, battery-backed timekeeping solutions.

Real Time Clock Replacement Considerations

The DS1340 is explicitly documented as being pin compatible and functionally equivalent to the ST M41T00. When substituting, verify that the replacement device supports the same I²C addressing and register map structure to ensure seamless integration into existing firmware.

Real Time Clock FAQ

How does the device handle power transitions?

The DS1340 utilizes a built-in power-sense circuit to detect when VCC falls below the power-fail voltage (VPF). It automatically switches to the VBACKUP supply, inhibiting read/write access while maintaining continuous timekeeping operations.

What is the function of the FT/OUT pin?

The FT/OUT pin can output a 512Hz test signal when the Frequency Test (FT) bit is set to logic 1. Alternatively, it reflects the state of the Output Control (OUT) bit when FT is logic 0.

How is clock accuracy calibrated?

Accuracy is adjusted using five calibration bits (CAL4–CAL0) and a sign bit (S) in the control register. Positive calibration inserts oscillator cycles to speed up the clock, while negative calibration blanks cycles to slow it down.