DS1340U-3+

Real Time Clock Overview

The DS1340U-3+ is a low-power real-time clock and calendar manufactured by Analog Devices Inc./Maxim Integrated. It operates within a supply voltage range of 2.7V to 5.5V, with a nominal rating of 3.0V. The device features an I²C bidirectional serial bus interface supporting standard (100kHz) and fast (400kHz) modes. It provides timekeeping for seconds, minutes, hours, day, date, month, and year, including automatic leap-year correction. Key specifications include a standby current of up to 125µA at 3.3V and a backup supply voltage range of 1.3V to 3.7V. The component is housed in an 8-pin µSOP package.

Real Time Clock Feature Summary

• I²C Serial Interface: Supports standard mode (100kHz) and fast mode (400kHz) communication via SDA and SCL pins.
• Trickle-Charger Capability: Includes programmable current-limiting resistors and diode selection on the VBACKUP pin for battery or supercapacitor charging.
• Automatic Power-Fail Detection: Built-in circuitry detects power failures below the power-fail voltage (VPF) and switches seamlessly to the backup supply while inhibiting register access.
• Oscillator Stop Flag (OSF): Edge-triggered flag indicates if the oscillator has stopped due to power loss or disabling, ensuring data validity checks.

Real Time Clock Applications

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

Real Time Clock Procurement Notes

Verify the specific suffix 'U-3+' corresponds to the 8-pin µSOP package and 3.0V nominal supply voltage. Confirm RoHS compliance status as indicated by the '+' designation. Ensure the design supports the required I²C pull-up voltages and crystal load capacitance specifications for accurate timing.

Real Time Clock Selection Notes

Select this variant for systems requiring a 3.0V nominal supply with a maximum operating voltage of 5.5V. The U-series denotes the surface-mount µSOP package. Consider the trickle-charger configuration requirements for the backup source, noting that the 250Ω resistor option is restricted when VCC exceeds 3.63V.

Real Time Clock Part Context

The DS1340U-3+ belongs to the DS1340 family of real-time clocks. It is functionally equivalent and pin-compatible with the ST M41T00. The 'U' suffix identifies the 8-pin µSOP package, distinguishing it from the SO package variants (Z suffix) and the integrated crystal SO package variants (C suffix).

Real Time Clock Replacement Considerations

The DS1340U-3+ is functionally equivalent to the ST M41T00. Other compatible variants within the same family include DS1340U-18+ (1.8V) and DS1340U-33+ (3.3V), provided the supply voltage constraints are met.