Analog Devices Inc./Maxim Integrated DS1629S+

Overview

DS1629S+ from Maxim Integrated is a 2-wire digital thermometer and real-time clock (RTC) IC in an 8-pin SO package, measuring temperature from −55°C to +125°C with ±2.0°C typical accuracy and 9-bit resolution, maintaining calendar time with leap-year compensation through 2100, and featuring a dedicated open-drain ALRM output for thermal or time alarms - used in battery-powered thermal data loggers and embedded microprocessor systems.

For engineers reviewing the DS1629S+ datasheet, DS1629S+ pinout, DS1629S+ application, or DS1629S+ equivalent, key selection criteria include its integrated RTC/thermometer co-location, 2.2V–5.5V supply range, 32-byte SRAM for local logging, programmable alarm trigger logic, and factory-calibrated delta-sigma temperature sensor requiring no external components.

Technical Context

The DS1629S+ integrates a bandgap-based temperature sensor with a delta-sigma ADC and a BCD-coded RTC driven by an external 32.768kHz crystal, with internal oscillator division configurable via OS0/OS1 bits (fO, fO/4, fO/8, or disabled). Its 2-wire interface operates up to 400kHz and supports master-initiated read/write to temperature, clock, alarm, configuration, and 32-byte SRAM registers.

Alarm behavior is fully programmable: ALRM activates on temperature ≥ TH (with hysteresis via TL), time match (minute-of-week), either event, or disabled; polarity (active-high/low) and conversion mode (one-shot/continuous) are controlled via nonvolatile configuration bits. The OSC pin provides buffered oscillator output usable as a microcontroller clock source.

Key Specifications

Pinout & Package

DS1629S+ is housed in an 8-pin SOIC package (150-mil width) with gull-wing leads, RoHS-compliant and lead-free per + suffix.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar thermometer-and-RTC applications.

Compared with DS3231M+ and MAX31820, the DS1629S+ uniquely combines calibrated temperature measurement, leap-year RTC, programmable dual-trigger ALRM, and local SRAM in a single 2-wire device - making it optimal for compact, battery-operated systems needing coordinated thermal and temporal awareness.

Availability

DS1629S+ is available at Aetrix Electronics and suitable for thermal data loggers, embedded PC peripherals, and battery-powered IoT sensors requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for DS1629S+ 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) is a U.S.-based semiconductor company specializing in precision analog, mixed-signal, and power management ICs for industrial, computing, and communications markets.

The DS1629S+ belongs to Maxim's legacy digital thermometer and RTC product line, designed specifically for space-constrained, low-power systems requiring tightly coupled time and temperature awareness without external support components.

FAQ

What is the temperature measurement accuracy and resolution of the DS1629S+?

The DS1629S+ achieves ±2.0°C typical accuracy across −55°C to +125°C and provides 9-bit resolution (0.5°C LSB). Higher effective resolution is attainable using the Read Counter (A8h) and Read Slope (A9h) commands to compute sub-LSB values via the formula T = TEMP_READ − 0.25 + (COUNT_REMAIN − COUNT_PER_C)/COUNT_PER_C. This capability is built into the DS1629S+ firmware and requires no external calibration.

Does the DS1629S+ require an external crystal, and what type is specified?

Yes, the DS1629S+ requires an external 32.768kHz tuning-fork crystal connected between X1 and X2 pins. The device includes internal load capacitance optimized for standard 12.5pF crystals, eliminating need for external capacitors. The oscillator output (OSC) can be configured to deliver fO, fO/4, or fO/8, or disabled entirely to reduce power consumption in the DS1629S+.

How does the DS1629S+ alarm output (ALRM) function, and can its polarity be changed?

The DS1629S+ ALRM pin is an open-drain output that activates when temperature ≥ TH or time matches the clock alarm setting - configurable via A0/A1 bits in the configuration register. Its active state (high/low) is controlled by the POL bit: POL = 0 (factory default) sets ALRM active-low; POL = 1 makes it active-high. Both settings are nonvolatile and persist across power cycles in the DS1629S+.

Can the DS1629S+ operate from a single-cell lithium battery, and what is its minimum supply voltage?

Yes, the DS1629S+ supports operation from a single-cell lithium battery, with a minimum VDD of 2.2V for RTC, SRAM retention, and 2-wire communication. Temperature conversions and EEPROM writes require ≥2.7V, but standby and alarm monitoring remain functional down to 2.2V - enabling reliable use across the full discharge curve of Li-ion (3.0–4.2V) or LiFePO₄ (2.5–3.65V) cells in the DS1629S+.

Is the DS1629S+ pin-compatible with other Maxim thermometer+RTC devices like the DS1621 or DS1722?

No, the DS1629S+ is not pin-compatible with DS1621 or DS1722. While all three use 8-pin SO packages, DS1621 has different pin assignments (e.g., no X1/X2 or OSC pins) and lacks RTC functionality. DS1722 is a standalone thermometer with different interface and no alarm or clock features. The DS1629S+ pinout - including dedicated X1, X2, OSC, and ALRM - is unique to its integrated RTC+thermometer architecture.