Analog Devices Inc./Maxim Integrated MAX31850NATB+T

Overview

MAX31850NATB+T from Maxim Integrated is a cold-junction compensated, 1-Wire thermocouple-to-digital converter optimized for N-type thermocouples. It delivers 14-bit resolution (0.25°C), supports -270°C to +1300°C measurement range, achieves ±2°C thermocouple accuracy from -200°C to +700°C, and operates from -40°C to +125°C ambient. It is used in industrial temperature monitoring systems where distributed, low-wiring-count sensing is required.

For engineers reviewing the MAX31850NATB+T datasheet, MAX31850NATB+T pinout, MAX31850NATB+T application, or MAX31850NATB+T equivalent, key selection considerations include its parasitic-power capability, 4-pin addressable location mapping, open/short fault detection on T+/T-, integrated cold-junction compensation, and compatibility with standard 1-Wire master controllers.

Technical Context

The MAX31850NATB+T integrates a precision 14-bit ADC, dedicated cold-junction temperature sensor, fault-detection circuitry for open/short conditions on T+ and T-, and 1-Wire interface logic-all in a single TDFN-EP package. Its internal signal conditioning handles N-type thermocouple sensitivity (36.256 µV/°C) and linearizes output using factory-trimmed gain/offset calibration.

It performs three concurrent operations during each 72–100 ms conversion cycle: cold-junction temperature digitization (0.0625°C resolution), thermocouple voltage conversion, and real-time fault scanning. Power delivery supports both local VDD supply and parasite power via DQ, with strong pullup required only during conversion.

Key Specifications

Pinout & Package

TDFN-EP (3mm × 4mm, 10-pin, exposed pad). Pin 10 is DNC; EP has no internal connection and may be grounded or left floating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX31855KASA+ and ADS1220IPWR, the MAX31850NATB+T uniquely combines N-type optimization, 1-Wire multdrop, parasitic power, and hardware fault flags - making it the only solution requiring zero external components for drop-in N-type thermocouple digitization in distributed systems.

Availability

MAX31850NATB+T is available at Aetrix Electronics and suitable for industrial process monitoring, HVAC zone sensing, and appliance oven control requiring stable component supply and long-term lifecycle support.

Supply support for MAX31850NATB+T 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, medical, and communications applications.

The MAX31850 product line delivers cold-junction compensated thermocouple interfaces with 1-Wire connectivity - engineered specifically for distributed, low-wiring-count temperature measurement in harsh environments.

FAQ

What thermocouple types does the MAX31850NATB+T support?

The MAX31850NATB+T is factory-trimmed and calibrated exclusively for N-type thermocouples. It implements the 36.256 µV/°C nominal sensitivity and nonlinear correction specific to N-type wire pairs (nicrosil/nisil). It does not support K-, J-, T-, E-, R-, or S-type thermocouples - those require other variants like MAX31850K or MAX31851R. Using an N-type thermocouple with MAX31850NATB+T ensures guaranteed accuracy within ±2°C over -200°C to +700°C.

Does the MAX31850NATB+T require an external power supply?

No - the MAX31850NATB+T supports both local VDD supply and parasite power via the DQ pin. In parasite mode, it draws operating current from the 1-Wire bus during high states and stores charge on an internal capacitor (CPP) to sustain operation during low states. However, a strong external pullup (e.g., MOSFET-switched rail) is mandatory during temperature conversions (72–100 ms) to deliver up to 1.5 mA. For continuous reliability above +100°C, external VDD is recommended.

How does the MAX31850NATB+T detect thermocouple faults?

The MAX31850NATB+T performs autonomous fault detection during every conversion cycle. It identifies open thermocouples (bit 0 high in byte 2), shorts to GND (bit 1 high), and shorts to VDD (bit 2 high) by analyzing bias current and voltage thresholds at T+ and T-. These flags appear in the internal temperature register (scratchpad bytes 2–3) and propagate to the thermocouple temperature register's sign bit. No external circuitry or firmware polling is needed - fault status is readable immediately after conversion.

What is the function of the AD0–AD3 pins on the MAX31850NATB+T?

The AD0–AD3 pins on the MAX31850NATB+T are hardwired location address inputs that encode a 4-bit binary value (0–15) representing the sensor's physical position. This value is latched at power-up and appears in bits [3:0] of the configuration register (scratchpad byte 4). It enables deterministic mapping of 1-Wire nodes - for example, AD0=1, AD1=0, AD2=1, AD3=0 encodes location "5", letting firmware associate readings with specific furnace zones or HVAC ducts without relying on ROM ID parsing.

What is the temperature accuracy specification for the MAX31850NATB+T over its full range?

The MAX31850NATB+T guarantees ±2°C thermocouple temperature accuracy for N-type measurements from -200°C to +700°C, and ±4°C from +700°C to +1300°C, under specified operating conditions (VDD = 3.0–3.6 V, TA = -40°C to +125°C). This includes contributions from ADC quantization, cold-junction compensation error (±2°C), and thermocouple nonlinearity - all validated per Maxim's six-sigma production testing. Accuracy degrades outside these ranges and is not specified below -270°C or above +1300°C.