DS1672-33

Real Time Clock Overview

The DS1672-33 is a real-time clock (RTC) featuring a 32-bit binary counter and power-monitoring functions. It operates on an I2C serial interface with a supply voltage range of 2.97V to 5.5V, typically centered at 3.3V. The device includes automatic power-fail detection and switching circuitry that transitions operation from VCC to a backup supply (VBACKUP) when the primary voltage drops below a threshold. It supports standard and fast-mode I2C communication up to 400kHz and maintains timekeeping via an external 32.768kHz crystal.

Real Time Clock Feature Summary

• 32-bit binary counter for time-of-day and calendar calculations
• I2C serial interface supporting Standard (100kHz) and Fast (400kHz) modes
• Automatic power-fail detect and switch circuitry with reset output
• Trickle-charge capability for battery or supercapacitor maintenance

Real Time Clock Applications

• Systems requiring precise timekeeping during power outages
• Data logging applications needing elapsed time counters
• Embedded devices utilizing I2C bus architecture
• Battery-powered equipment requiring low standby current

Real Time Clock Procurement Notes

Verify the specific package variant required, as the DS1672 family includes PDIP, SO, and µSOP options. Confirm RoHS compliance status by checking for the '+' suffix in the ordering part number. Ensure the selected component matches the system's voltage requirements, noting that the -33 suffix indicates a nominal 3.3V operation range. Check availability as lead times may vary by manufacturer distribution channels.

Real Time Clock Selection Notes

Select the DS1672-33 when a 3.3V nominal supply is available but the system requires robust power-fail protection. Compare against other RTCs if lower voltage operation (e.g., 1.8V) is needed, in which case the DS1672-2+ might be more suitable. Consider the trickle charger configuration if direct battery charging from VCC is desired, ensuring resistor values comply with maximum voltage limits. Verify I2C address compatibility with the host microcontroller.

Real Time Clock Part Context

The DS1672 is part of Maxim Integrated's (now Analog Devices) line of real-time clocks designed for low-power applications. It integrates a precision temperature-compensated reference and comparator circuit to monitor VCC. The device is UL recognized for safety when used with lithium batteries. It serves as a drop-in replacement for older Dallas Semiconductor RTCs while offering enhanced power management features.

Real Time Clock Replacement Considerations

Direct pin-compatible replacements within the same series include DS1672-2+ (2.0V) and DS1672-3+ (3.0V). For different packages, ensure electrical parameters match; for example, the DS1672S variants offer SO packaging. Verify that any substitute supports the required I2C speed and has compatible register maps if software migration is involved.

Real Time Clock FAQ

How does the DS1672 handle power failure?

When VCC drops below the power-fail trip point (VPF), the RST signal goes active, and the device automatically switches to the VBACKUP supply to maintain oscillator and counter operation.

What is the function of the EOSC bit?

The EOSC bit (bit 7 of the control register) controls the oscillator in backup mode. Setting it to logic 1 stops the oscillator to reduce current consumption, while logic 0 starts it.

Can the DS1672 charge a battery directly?

Yes, it features a programmable trickle charger. Users can select resistor and diode configurations via the trickle charger register to manage charging current from VCC to VBACKUP.