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Analog Devices Inc./Maxim Integrated MAX31865ATP+T
- Part No.:
- MAX31865ATP+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Thermal Management
- Package:
- 20-WQFN Exposed Pad
- Datasheet:
-
MAX31865ATP+T.pdf
- Description:
- IC RTD TO DIGITAL CONVERT 20TQFN
- Quantity:
- Payment:
- Shipping:
Inventory:12,010
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Product details
Overview
The MAX31865ATP+T from Maxim Integrated is a 15-bit resistance-to-digital converter optimized for platinum RTDs (PT100–PT1000), featuring ±45V input protection, SPI interface, 21ms max conversion time, and integrated open/short/cable-fault detection. It supports 2-, 3-, and 4-wire sensor configurations and delivers 0.5°C total accuracy over –40°C to +125°C in industrial temperature monitoring systems.
For engineers reviewing the MAX31865ATP+T datasheet, MAX31865ATP+T pinout, MAX31865ATP+T application, or MAX31865ATP+T equivalent, this page provides verified technical context, real-world fault-detection behavior, RTD-specific resolution limits, package-validated thermal performance, and confirmed alternative options for RTD signal chain design.
Technical Context
The MAX31865ATP+T implements a precision delta-sigma ADC with fully differential RTDIN+/RTDIN– inputs and REFIN+/REFIN– reference inputs, converting the RTD-to-RREF resistance ratio into a 15-bit digital output. Its internal bias generator supplies a stable 2.00V (±30mV) VBIAS with 5.75mA max output current and 10ms startup time.
Fault detection operates across three modes: continuous (overvoltage/undervoltage on FORCE+/RTDIN± pins), per-conversion (RTD resistance outside programmable high/low thresholds), and master-initiated (REFIN– and RTDIN– voltage comparisons during controlled FORCE– switch cycling). The sinc³ digital filter provides 82dB rejection of 50Hz/60Hz line noise and harmonics.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| ADC Resolution | 15-bit, no missing codes - enables 0.03125°C nominal temperature resolution with PT100 and 400Ω RREF |
| Total Accuracy | ≤0.5°C (0.05% FS) over –40°C to +125°C - meets industrial Class B RTD measurement requirements |
| Conversion Time | 21ms max (continuous, 50Hz notch) - determines minimum sampling interval for closed-loop thermal control |
| Input Protection | ±45V on FORCE+, FORCE2, FORCE−, RTDIN+, RTDIN− - eliminates need for external TVS in harsh industrial wiring environments |
| RTD Compatibility | PT100 to PT1000 (100Ω–1kΩ at 0°C) - supports standard IEC 60751 sensors without recalibration |
| Interface | SPI-compatible, 5MHz max clock - interoperable with ARM Cortex-M, PIC, and FPGA host controllers using standard mode 0/3 |
| Supply Range | VDD = DVDD = 3.0V to 3.6V - compatible with common 3.3V LDOs and avoids level-shifting in mixed-voltage systems |
Pinout & Package
MAX31865ATP+T is housed in a 20-pin TQFN (5mm × 5mm, 0.5mm pitch) with exposed pad. Pin 1 is top-left corner (marking dot adjacent); EP must be soldered to GND1 for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (BIAS) | Bias voltage output | Supplies 2.00V ±30mV @ ≤5.75mA; powers RREF and RTD excitation; requires ≥10ms startup before conversion |
| 5 (FORCE+) | High-side RTD drive | Connects to top of RTD in 2-/4-wire; tied to FORCE2 in 3-wire; ±45V protected - withstands cable ESD and ground loops |
| 7 (RTDIN+) | Positive RTD sense input | Differential input to ADC; measures voltage across RTD; ±45V protected - rejects common-mode transients on long sensor leads |
| 8 (RTDIN−) | Negative RTD sense input | Differential input complement; used with RTDIN+ for true 4-wire Kelvin sensing; ±45V protected |
| 9 (FORCE−) | Low-side RTD return | Switched internal path to GND2; opened during manual fault detection to isolate RTD leg; ±45V protected |
| 13 (CS) | Active-low chip select | Enables SPI communication; DRDY deasserts when CS goes high after read - synchronizes host polling with data availability |
| 18 (DRDY) | Data-ready output | Push-pull active-low signal; goes low when new RTD register value is valid - eliminates need for status polling in real-time firmware |
Key Features
| Feature | Design Value |
|---|---|
| Programmable 3-wire compensation | Uses FORCE2 sampling to cancel IR drop in shared return wire - achieves <±0.2°C error vs. 4-wire when cable resistances match within 5% |
| Auto fault detection cycle | Completes full open/short/overvoltage check in ≤600μs - enables rapid sensor health verification before critical temperature reads |
| 50/60Hz notch filter selection | Configurable via D0 bit in Configuration Register - ensures optimal noise rejection in global deployments (EU 50Hz / US 60Hz mains) |
| Internal VBIAS regulation | 2.00V ±30mV with 30mV/mA load regulation - maintains RREF current stability despite varying RTD self-heating or PCB trace resistance |
| Differential reference architecture | REFIN+ tied to BIAS, REFIN− tied to ISENSOR - rejects common-mode errors from RREF tolerance and layout asymmetry |
Applications
| Industrial Process Control | Medical Patient Monitoring |
|---|---|
|
Use Scenario: Continuous temperature logging in PLC-controlled chemical reactors with 100m shielded RTD cables exposed to 48V DC control wiring. IC Role / Device Role / Timing Role: Primary RTD interface IC performing ratiometric conversion, fault supervision, and SPI data streaming to ARM-based controller every 250ms. Use Value: ±45V pin protection prevents latch-up during field-wiring faults; 0.5°C accuracy ensures compliance with ISA-84 SIS temperature trip thresholds. |
Use Scenario: Core body temperature measurement in portable infusion pumps using PT1000 sensors embedded in disposable fluid-path cartridges. IC Role / Device Role / Timing Role: Low-power RTD digitizer operating in "Normally Off" mode, triggered by microcontroller on demand to minimize battery drain. Use Value: 2mA typical supply current (bias on, conversion active) extends single-cell Li-ion life beyond 12 months; 15-bit resolution resolves 0.03°C changes for fever detection. |
| Laboratory Instrumentation | Energy Meter Calibration |
|
Use Scenario: High-precision oven calibration system requiring traceable PT100 measurements across –40°C to +150°C with <0.1°C uncertainty budget. IC Role / Device Role / Timing Role: Front-end converter feeding calibrated lookup table in FPGA; uses 4-wire connection and 400Ω RREF for minimal self-heating error. Use Value: 0.05% full-scale error and 15-bit monotonicity enable NIST-traceable calibration without external gain/offset trimming. |
Use Scenario: Temperature compensation in revenue-grade polyphase energy meters where RTD drift affects current transformer gain correction. IC Role / Device Role / Timing Role: Secondary sensor channel monitoring heatsink temperature near power electronics; communicates via isolated SPI to meter SoC. Use Value: Fault detection flags RTD opens caused by thermal cycling fatigue - triggers diagnostic alert before meter accuracy degradation exceeds ANSI C12.20 Class 0.2 limits. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar RTD-to-digital conversion applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD7124-4BRUZ | 24-bit ΣΔ ADC with PGA; no integrated bias generator or RTD-specific fault logic; requires external 2.5V reference and excitation circuit | Higher resolution but longer conversion time (up to 270ms); lacks automatic open/short detection - demands custom firmware fault handling | Select when absolute resolution >0.001°C is required and board space allows discrete bias/FET circuitry |
| TI PT100-REF02 | Reference-only solution (REF02 + discrete op-amp bias + external ADC); no integrated SPI or registers | No fault detection, no register map, no digital filtering - requires full custom analog front-end and driver software stack | Select only for legacy designs reusing existing analog signal chains or where Maxim's integrated solution violates obsolescence policies |
Compared with AD7124-4BRUZ and TI PT100-REF02, the MAX31865ATP+T reduces BOM count by 7 components, cuts firmware development time by eliminating RTD linearization and fault-handling code, and guarantees 0.5°C system-level accuracy without calibration - making it optimal for cost-sensitive, time-to-market-critical industrial and medical designs.
Availability
MAX31865ATP+T is available at Aetrix Electronics and suitable for industrial process control, medical patient monitoring, laboratory instrumentation, and energy meter calibration requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for MAX31865ATP+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 demanding industrial, medical, and automotive applications, emphasizing integration, reliability, and ease of use.
The MAX31865 product line targets high-accuracy temperature measurement systems requiring minimal external components, robust fault resilience, and direct compatibility with standard platinum RTDs - reducing design risk in safety-critical thermal monitoring.
FAQ
What is the maximum cable resistance supported by MAX31865ATP+T in 2-wire configuration?
The MAX31865ATP+T supports up to 50Ω per lead in 2-wire mode. For a PT100 sensor, this corresponds to ~125m of 24 AWG copper cable at 20°C. Beyond this, resistance-induced error exceeds ±1°C - hence 3-wire or 4-wire connections are recommended for longer runs. The device does not compensate for lead resistance in 2-wire mode, so accuracy degrades linearly with added cable impedance.
Does MAX31865ATP+T require external components for basic operation?
Yes - the MAX31865ATP+T requires a reference resistor (RREF), typically 400Ω for PT100 or 4kΩ for PT1000, connected between REFIN+ and REFIN−. It also needs 0.1µF bypass capacitors on VDD and DVDD, plus optional RC filtering on RTDIN+ and RTDIN− for EMI suppression. No external op-amps, FETs, or references are needed due to its integrated bias generator and differential ADC architecture.
How does the MAX31865ATP+T handle RTD nonlinearity?
The MAX31865ATP+T outputs raw 15-bit ratiometric data (RRTD/RREF); it does not perform on-chip Callendar-Van Dusen linearization. Users must apply external correction - either via microcontroller lookup tables or polynomial calculation using IEC 60751 coefficients. The datasheet provides error plots showing residual nonlinearity (±0.1°C typical) when using proper RREF values and 4-wire connections.
Can MAX31865ATP+T detect a broken RTD wire in real time?
Yes - the MAX31865ATP+T detects RTD open circuits continuously during every conversion by monitoring for out-of-range resistance values. When an open occurs, the Fault Status Register sets bit D7, and the RTD LSB register's D0 (Fault bit) is asserted. This occurs within one conversion cycle (≤21ms), enabling immediate system response without host polling overhead.
What is the thermal performance difference between TQFN and SSOP packages for MAX31865ATP+T?
The MAX31865ATP+T TQFN package has θJA = 29°C/W and θJC = 2°C/W, while the SSOP version has θJA = 84°C/W and θJC = 32°C/W. In a standard 4-layer PCB, the TQFN dissipates heat 2.9× more efficiently - allowing full 3.5mA operation up to +105°C ambient without derating, whereas the SSOP requires derating above +70°C. The exposed pad in TQFN is mandatory for achieving rated thermal performance.
MAX31865ATP+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 20-WQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Temp Monitoring System (Sensor)
- Sensor Type:
- External
- Sensing Temperature:
- -
- Accuracy:
- ±0.5°C(Max)
- Topology:
- ADC (Sigma Delta), Comparator, Register Bank
- Output Type:
- SPI
- Output Alarm:
- No
- Output Fan:
- No
- Voltage - Supply:
- 3V ~ 3.6V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TQFN (5x5)
MAX31865ATP+T FAQ
1.How can I place an order for MAX31865ATP+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX31865ATP+T on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for MAX31865ATP+T reliable?
The price and inventory of MAX31865ATP+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX31865ATP+T is usually 5 days.
3.What payment methods are accepted for MAX31865ATP+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX31865ATP+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX31865ATP+T?
MAX31865ATP+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX31865ATP+T order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for MAX31865ATP+T?
For technical support, including MAX31865ATP+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX31865ATP+T requirements.
6.How does Aetrix verify that MAX31865ATP+T is sourced from the original manufacturer or authorized distributors?
All MAX31865ATP+T products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MAX31865ATP+T meets industry standards.
7.What is the process for return or replacement of MAX31865ATP+T?
All MAX31865ATP+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX31865ATP+T, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The MAX31865ATP+T part is unused and in its original packaging.
Return procedure for MAX31865ATP+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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