Analog Devices Inc./Maxim Integrated DS1631U+

Overview

DS1631U+ from Maxim Integrated is a high-precision digital thermometer and thermostat IC with 9–12-bit user-selectable resolution, ±0.5°C accuracy from 0°C to +70°C (VDD = 3.0–5.5V), and -55°C to +125°C operating range. It features nonvolatile TH/TL trip-point registers, push-pull TOUT output, and 2-wire (I²C-compatible) interface - used for thermal monitoring in space-constrained embedded systems such as network routers and cellular base stations.

For engineers reviewing the DS1631U+ datasheet, DS1631U+ pinout, DS1631U+ application, or DS1631U+ equivalent, key selection considerations include its µSOP-8 package, NV EEPROM-based thermostat configuration, 750ms max conversion time at 12-bit resolution, I²C multidrop support (up to 8 devices), and standalone thermostat capability (when configured as DS1631A variant).

Technical Context

The DS1631U+ implements a bandgap-based temperature sensor with delta-sigma ADC, delivering calibrated °C output via 2-wire serial interface. Its configuration register controls resolution (R0/R1 bits), TOUT polarity (POL), and conversion mode (1SHOT bit), with POL and 1SHOT stored in EEPROM for power-up persistence.

Thermostat operation compares real-time temperature against user-programmed TH/TL registers (stored in NV EEPROM), updating push-pull TOUT after each conversion. The device supports both continuous and one-shot modes, with DONE flag indicating conversion completion and THF/TLF flags recording historical temperature excursions.

Key Specifications

Pinout & Package

DS1631U+ is packaged in an 8-pin µSOP (micro Small Outline Package), 3.0mm × 3.0mm body, 0.5mm pitch, exposed pad optional - optimized for high-density PCB layouts in portable and telecom equipment.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital thermometer and thermostat applications.

Compared with DS1631U+, DS1631AU+ offers identical hardware with preconfigured autonomous operation, while DS1731U+ trades accuracy for lower cost - neither is pin-compatible replacement without firmware validation due to differing power-up behavior and error specifications.

Availability

DS1631U+ is available at Aetrix Electronics and suitable for network infrastructure, telecom base stations, and portable electronics requiring stable component supply, long-term thermal calibration integrity, and I²C multidrop scalability.

Supply support for DS1631U+ 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 and mixed-signal ICs for industrial, communications, and computing markets, with emphasis on reliability and integration.

The DS1631U+ belongs to Maxim's high-accuracy digital temperature sensor family, engineered specifically for embedded thermal management where NV configurability, low power, and I²C simplicity are critical.

FAQ

What is the default temperature resolution at power-up for DS1631U+?

The DS1631U+ powers up with 12-bit resolution (R1=1, R0=1), providing 0.0625°C temperature steps. This setting can be changed via the Configuration Register's R0 and R1 bits. Conversion time scales accordingly: 750ms at 12-bit versus 93.75ms at 9-bit. The DS1631U+ does not auto-start conversions at power-up - a Start Convert T command is required to begin measurement.

Does DS1631U+ support true I²C communication, and what are its timing limits?

Yes, DS1631U+ implements a standard-mode 2-wire interface compatible with I²C specifications: maximum SCL frequency is 400kHz, bus capacitance limit is 400pF, and timing parameters (tLOW, tHIGH, tSU:DAT, etc.) meet I²C requirements per Figure 3. It uses open-drain SDA and push-pull–compatible SCL, requiring only external pull-ups on SDA - no additional level-shifting or protocol translation is needed for integration with standard I²C masters.

How is thermostat hysteresis implemented in DS1631U+?

Hysteresis in DS1631U+ is implemented by independently programming upper (TH) and lower (TL) trip-point registers stored in NV EEPROM. TOUT transitions high when temperature ≥ TH and remains high until temperature falls below TL - the difference (TH − TL) defines hysteresis width. Both registers are two's complement, match the selected resolution, and retain values across power cycles, enabling robust thermal switching without software intervention.

Can DS1631U+ operate as a standalone thermostat without a microcontroller?

No - unlike the DS1631AU+ variant, the DS1631U+ powers up in low-power idle mode and requires a Start Convert T command to initiate temperature measurements. Autonomous thermostat operation is only available on DS1631AU+, which defaults to continuous conversion at power-up. For DS1631U+, full functionality (including TOUT assertion) depends on host MCU issuing commands via the 2-wire interface.

What is the role of the THF and TLF flags in DS1631U+ configuration register?

The THF (Temperature High Flag) and TLF (Temperature Low Flag) are status bits in the DS1631U+ Configuration Register that latch once - THF sets to 1 if temperature ever exceeds TH since power-on, and TLF sets to 1 if temperature ever falls below TL. They remain asserted until cleared by software or power cycle, enabling diagnostic logging of thermal excursions even during intermittent MCU operation or sleep states.