MCP9700AT-E/TT: A Comprehensive Technical Overview of Microchip's Linear Active Thermistor IC
The MCP9700AT-E/TT from Microchip Technology represents a significant advancement in temperature sensing, offering a highly integrated and linear alternative to traditional negative temperature coefficient (NTC) thermistors. This analog active thermistor IC simplifies system design by converting temperature directly into an analog voltage signal with a predictable, factory-calibrated response, eliminating the complex signal conditioning often required with other sensing technologies.
Key Architecture and Operating Principle
At its core, the MCP9700AT-E/TT integrates a precision bandgap temperature sensor core with a specialized conditioning circuit. Unlike an NTC, whose resistance changes exponentially with temperature, this IC is designed to provide a linear voltage output directly proportional to the ambient temperature. The device operates from a single power supply ranging from 3.1V to 5.5V, making it exceptionally suited for low-power and battery-operated applications, including portable medical devices, HVAC systems, and consumer electronics.
The output voltage (VOUT) follows a simple, predefined transfer function:
VOUT = TC × TA + V0°C
Where:
`TC` is the temperature coefficient, typically 10.0 mV/°C.
`TA` is the ambient temperature.
`V0°C` is the output voltage at 0°C, typically 500 mV.
This straightforward linear equation allows a microcontroller's analog-to-digital converter (ADC) to easily calculate the temperature with minimal computational overhead, streamlining firmware development.
Performance Characteristics and Advantages
The MCP9700AT-E/TT is designed for a temperature range of -40°C to +125°C, covering a vast array of industrial, commercial, and automotive environments. Its accuracy is specified at ±2°C (max.) at +25°C and ±4°C (max.) from 0°C to +70°C, providing sufficient precision for a wide range of monitoring and control applications.
A critical advantage of this device is its low power consumption, with a typical quiescent current of just 12 µA. This ultra-low current draw is paramount for applications where power budgets are extremely constrained. Furthermore, the IC is packaged in a space-saving SOT-23-3 package, which is ideal for modern, compact PCB designs. The "A" grade version ensures a higher accuracy specification compared to the standard version, providing better performance for more demanding tasks.
Application Circuit and Design Considerations
Implementing the MCP9700AT-E/TT is remarkably simple. The basic circuit requires only a single bypass capacitor (typically 0.1 µF) placed close to the VDD pin for stability and noise immunity. The output voltage can be connected directly to a microcontroller's ADC input.
For optimal performance, designers should consider:
Noise Filtering: Adding a small RC filter on the output can help reduce noise, especially in electrically noisy environments.
ADC Reference: The accuracy of the temperature reading is directly dependent on the stability and accuracy of the ADC's voltage reference. Any error in the reference will directly translate to a temperature measurement error.
Self-Heating: Due to its extremely low power consumption, the self-heating effect is negligible, minimizing measurement drift caused by the sensor itself.
Conclusion and Summary by ICGOODFIND
ICGOODFIND: The MCP9700AT-E/TT stands out as an exemplary solution for designers seeking to replace NTC thermistors and their associated complexity. Its integrated linear output, ultra-low power operation, and simple 3-wire interface drastically reduce design time and system cost. By delivering a ready-to-measure analog voltage, it provides a reliable, compact, and efficient method for accurate temperature acquisition across a broad spectrum of electronic systems.
Keywords: Linear Active Thermistor IC, Low Power Consumption, Analog Temperature Sensor, SOT-23 Package, Microchip Technology.
