Precision RTD front-end in a 20-SSOP
The MAX31865AAP+ integrates a sigma-delta ADC, comparator, and register bank to convert a platinum RTD's resistance directly to a digital temperature reading over SPI — no external signal chain needed. Its ±0.5°C maximum accuracy means the measurement error budget for the full system — including RTD tolerance, reference resistor drift, and PCB thermocouple effects — starts from this floor. For a Class A PT100, the combined error at 100°C is roughly ±0.7°C, tight enough for industrial process monitoring or medical thermometry.
Supply rail and temperature envelope
Operates from 3V to 3.6V, matching common 3.3V digital rails — the same supply that powers the host MCU's SPI port. No separate analog rail is required, which simplifies the power tree. The 20-SSOP package keeps the die temperature within spec when the PCB sees airflow or a heatsink under the exposed pad.