Analog Devices Inc./Maxim Integrated DS1672U-33

Overview

DS1672U-33 from Maxim Integrated is a battery-backed, I²C-compatible 32-bit real-time counter with integrated power-fail detection and reset generation. It operates from a 3.3V primary supply (VCC = 2.97–5.5V), features low-voltage oscillator operation down to 1.3V on VBACKUP, and maintains timekeeping during main power loss using a standard 3V lithium cell. It is used in embedded systems requiring tamper-resistant, nonvolatile time-stamping and microprocessor supervision.

For engineers reviewing the DS1672U-33 datasheet, DS1672U-33 pinout, DS1672U-33 application, or DS1672U-33 equivalent, key selection criteria include its 32-bit binary counter resolution, I²C fast-mode (400kHz) support, programmable trickle-charge circuitry, temperature-compensated power-fail threshold (VPF = 1.58–1.80V), and µSOP-8 package compatibility with space-constrained industrial control and metering designs.

Technical Context

The DS1672U-33 implements a dedicated 32-bit binary counter incremented at 1Hz via an internal divider chain driven by a 32.768kHz crystal oscillator. Its power-monitoring circuit uses a precision, temperature-compensated voltage reference and comparator to detect VCC falling below VPF (1.58–1.80V), triggering an active-low open-drain RST signal with 250ms minimum assertion time upon recovery.

Communication occurs exclusively over a bidirectional I²C interface (slave address 0xD0 for write, 0xD1 for read) supporting both standard (100kHz) and fast (400kHz) modes. The device includes a programmable trickle-charger register (TCS=1010 pattern required) enabling selectable diode/resistor configurations (e.g., one diode + 2kΩ) for controlled backup-supply charging.

Key Specifications

Pinout & Package

DS1672U-33 is housed in an 8-pin µSOP package (3mm × 3mm, 0.5mm pitch), optimized for compact PCB layouts in portable and industrial equipment.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time counter applications.

Compared with DS1337+T&R and PCF8563T/1,118, the DS1672U-33 uniquely combines 32-bit counter depth, integrated power-fail reset, UL-recognized trickle charging, and guaranteed operation down to 1.3V on VBACKUP-making it irreplaceable in high-integrity, long-term timekeeping applications.

Availability

DS1672U-33 is available at Aetrix Electronics and suitable for smart metering, industrial control, and medical device applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for DS1672U-33 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power management ICs for industrial, automotive, and computing markets.

The DS1672U-33 belongs to Maxim's legacy real-time counter family, engineered specifically for robust, battery-backed timekeeping and microprocessor supervision in harsh environments.

FAQ

What is the primary function of the DS1672U-33?

The DS1672U-33 is a 32-bit binary counter with integrated power-fail detection and I²C interface. Its core function is to maintain accurate, battery-backed timekeeping (in seconds) and generate a hardware reset signal when main supply voltage drops below a temperature-compensated threshold. Unlike calendar RTCs, it provides raw counter values for software-based date/time derivation, making DS1672U-33 ideal for applications needing long-duration monotonic timing and fail-safe supervision.

Does the DS1672U-33 support direct calendar date/time output?

No, the DS1672U-33 does not output calendar date or time-of-day directly. It provides only a 32-bit binary count of elapsed seconds (0–4,294,967,295), which must be converted to calendar format (year/month/day/hour/minute/second) in host firmware. This architecture avoids internal calendar logic complexity and ensures DS1672U-33 retains full counter resolution and deterministic behavior across leap years and daylight saving transitions.

What is the significance of the "U" in DS1672U-33?

The "U" in DS1672U-33 denotes the µSOP-8 package variant (3mm × 3mm, 0.5mm pitch), distinguishing it from PDIP-8 ("DS1672-33") and SO-8 ("DS1672S-33") versions. This package enables high-density PCB layouts in space-constrained applications like handheld meters and portable diagnostics, while maintaining identical electrical functionality and pinout mapping as other variants.

Can the DS1672U-33 operate without a backup battery?

Yes, the DS1672U-33 can operate without a backup battery, but with critical limitations: VBACKUP must be grounded to disable backup mode, and timekeeping will cease immediately upon VCC loss. In this configuration, DS1672U-33 retains power-fail detection and reset generation, but loses its defining capability-continuous, nonvolatile timekeeping. For full functionality, a 1.3–3.63V backup source (e.g., CR2032) is required on VBACKUP.

How does the DS1672U-33 handle I²C communication during power transitions?

The DS1672U-33 disables I²C read/write access when VCC falls below the power-fail threshold (VPF = 1.58–1.80V), preventing data corruption. During this state, the SDA and SCL lines enter high-impedance mode, and the device ignores bus activity. Upon VCC recovery above VPF, DS1672U-33 resumes full I²C slave operation only after the RST signal deasserts (≥250ms delay), ensuring stable power before re-engaging the bus.