Analog Devices Inc./Maxim Integrated MAX31851SATB+

Overview

MAX31851SATB+ from Maxim Integrated is a cold-junction compensated, 1-Wire thermocouple-to-digital converter optimized for S-type thermocouples. It delivers 14-bit resolution (0.25°C), supports temperature measurement from −50°C to +1768°C, achieves ±2°C accuracy over −50°C to +700°C, and integrates fault detection for open/shorted thermocouples - enabling precise industrial furnace monitoring with minimal wiring.

For engineers reviewing the MAX31851SATB+ datasheet, MAX31851SATB+ pinout, MAX31851SATB+ application, or MAX31851SATB+ equivalent, key selection considerations include its S-type thermocouple support, parasitic power capability, 10-pin TDFN-EP package with location address inputs, and cold-junction compensation accuracy of ±2°C at 0°C to +70°C ambient.

Technical Context

The MAX31851SATB+ implements a dedicated analog front-end with programmable gain and offset correction tailored to S-type thermocouples (9.587 µV/°C nominal sensitivity), coupled with an internal 14-bit ADC and die-temperature sensor for real-time cold-junction compensation. Its conversion architecture separates thermocouple voltage sampling, cold-junction sensing, and fault detection into sequential phases within a single 72–100 ms cycle.

It operates exclusively via the 1-Wire interface (DQ pin), supporting both local VDD supply and parasite power modes. Four address pins (AD0–AD3) enable hardware-programmable device addressing on shared buses, while the unique 64-bit ROM ID allows unambiguous multi-drop identification without software enumeration overhead.

Key Specifications

Pinout & Package

MAX31851SATB+ uses a 10-pin 3mm × 4mm TDFN-EP package with exposed pad (EP) for thermal dissipation. Pin 10 (DNC) is not connected internally and must remain unconnected. The exposed pad may be soldered to ground for improved thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar thermocouple digitization applications.

Compared with MAX31855KASA+, MAX31851SATB+ provides S-type compatibility and hardware addressability; compared with AD8495ARZ, it delivers complete digital sensor subsystem functionality - eliminating external components, calibration effort, and bus protocol implementation.

Availability

MAX31851SATB+ is available at Aetrix Electronics and suitable for industrial furnace monitoring, HVAC combustion control, medical sterilization autoclaves, and power generation turbine inlet sensing requiring stable component supply and long-lifecycle assurance.

Supply support for MAX31851SATB+ 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 demanding industrial, medical, and communications applications.

The MAX31851SATB+ belongs to Maxim's thermocouple interface product line, engineered specifically for high-temperature, low-wiring-count sensor networks using S-, R-, or other noble-metal thermocouples in mission-critical environments.

FAQ

What thermocouple types does the MAX31851SATB+ support?

The MAX31851SATB+ is factory-calibrated exclusively for S-type thermocouples, with nominal sensitivity of 9.587 µV/°C and guaranteed accuracy across −50°C to +1768°C. It does not support K-, J-, N-, T-, R-, or E-type thermocouples - those require other variants such as MAX31850K or MAX31851R. Using an S-type thermocouple is mandatory to achieve the specified ±2°C cold-junction compensated accuracy.

Does the MAX31851SATB+ require an external power supply?

No - the MAX31851SATB+ supports parasite power mode, drawing operating current from the 1-Wire bus via the DQ pin when the bus is high. In this mode, VDD must be connected to GND. However, for temperature conversions above +100°C or in electrically noisy environments, local VDD supply (3.0–3.7 V) is recommended to ensure communication reliability and avoid leakage-related bus failures.

How does the MAX31851SATB+ handle thermocouple fault conditions?

The MAX31851SATB+ performs automatic fault detection during each conversion cycle, identifying open circuits, shorts to GND, and shorts to VDD on the T+ and T− inputs. Fault status is encoded in bits 0–2 of scratchpad byte 2: bit 0 = open, bit 1 = short to GND, bit 2 = short to VDD. When any fault is detected, bit 0 of the thermocouple temperature register (byte 0) is set high - providing immediate, hardware-flagged alerting without polling overhead.

What is the purpose of the AD0–AD3 pins on the MAX31851SATB+?

The AD0–AD3 pins on the MAX31851SATB+ provide hardware-programmable 4-bit location addressing, allowing up to 16 uniquely identifiable devices on the same 1-Wire bus without software configuration. These pins are read-only in the configuration register (scratchpad byte 4) and enable deterministic node mapping in factory-assembled sensor arrays - critical for automated calibration, maintenance tracking, and fault isolation in large-scale industrial deployments.

What is the temperature resolution and accuracy of the MAX31851SATB+?

The MAX31851SATB+ provides 0.25°C temperature resolution in its 14-bit thermocouple data register. Its cold-junction compensated accuracy is ±2°C for S-type thermocouples over −50°C to +700°C at ambient temperatures of 0°C to +70°C, and ±7°C over the full −40°C to +125°C operating range. Internal cold-junction sensing accuracy is ±2°C (−40°C to +100°C), and long-term drift is limited to ±0.24°C at +400°C hot junction.