LM75ADP Temperature Sensor
Overview
The Boardoza LM75A is a precision temperature-to-digital converter module based on the highly integrated NXP LM75ADP architecture. It utilizes an on-chip bandgap temperature sensor paired with a Sigma-Delta analog-to-digital converter to deliver high-resolution thermal data.
Beyond simple measurement, the device functions as a sophisticated thermal watchdog. It includes an integrated over-temperature detection output (OS) that can operate independently as a standalone thermostat upon power-up, making it invaluable for system protection in industrial control units, power supplies, and personal computing hardware.
Core Technical Specifications
The module is defined by the following operational parameters:
Sensing Architecture: On-chip bandgap sensor with an integrated 11-bit Sigma-Delta ADC.
Resolution: Provides a fine temperature resolution of 0.125 °C, allowing for the detection of minute thermal gradients.
Operating Voltage: Versatile supply range from 2.8 V to 5.5 V, ensuring compatibility with both low-voltage MCUs and standard 5V logic.
Accuracy:
±2 °C within the critical range of −25 °C to +100 °C.
±3 °C across the extended range of −55 °C to +125 °C.
Communication Interface: Industry-standard I2C-bus interface supporting up to 8 devices on a single bus via selectable addresses.
Power Efficiency: Features a low-power shutdown mode consuming only 3.5 µA, ideal for battery-constrained IoT nodes.
Robustness: ESD protection exceeding 2000 V (HBM) and latch-up immunity >100 mA, meeting strict JEDEC industrial standards.
Physical Dimensions: Compact 20 mm x 20 mm square footprint.
Key Engineering Features
Enhanced Resolution and Compatibility
Designed as a pin-for-pin replacement for the industry-standard LM75, the LM75A offers a significant upgrade in resolution (11-bit vs 9-bit) while maintaining full backward compatibility. This allows engineers to drop it into legacy designs to instantly improve thermal tracking precision without firmware overhaul.
Programmable Thermal Watchdog
The module features a dedicated Overtemp Shutdown (OS) pin with programmable hysteresis and threshold set points. This open-drain output can be configured to trigger an interrupt or directly drive a cooling fan when temperatures exceed safe limits, operating entirely in hardware without constant microcontroller polling.
Versatile I2C Addressing
To facilitate complex sensor networks, the board supports address selection. This feature enables the simultaneous operation of up to 8 distinct LM75A modules on the same 2-wire bus, simplifying multi-point thermal monitoring in large enclosures or battery packs.
Hardware Interface and Signal Mapping
The module interfaces via a standard 5-pin header, supporting mixed-voltage environments:
Power and Ground
VCC: Power supply input, accepting a wide range from 2.8V to 5.5V DC.
GND: Common system ground.
Digital Interface
SDA: I2C-bus bidirectional serial data line. This is an open-drain pin requiring a pull-up resistor (typically included on-board or required externally).
SCL: I2C-bus serial clock input.
OS (Overtemp Shutdown): Open-drain thermal alert output. Active when the measured temperature exceeds the programmed limit.
Applications
System Thermal Management: Critical component monitoring for servers, routers, and base stations.
Environmental Control: Precision thermostats for HVAC systems and office automation.
Industrial Process Control: Over-temperature protection for motor drivers and power inverters.
Personal Electronics: Thermal throttling logic for laptops and gaming consoles.
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