Microchip's Linear Active Thermistor™ ICs are temperature sensors whose output voltage is directly proportional to measured temperature. Unlike thermistors which are resistive sensors, the Linear Active Thermistor™ IC does not require any additional signal-conditioning circuit. Therefore, the biasing circuit development overhead for thermistor solutions can be avoided by implementing this low-cost device. The Voltage Output pin (VOUT) can be directly connected to the ADC input of a microcontroller.
The MCP9700 can accurately measure temperature from -40°C to +150°C. The output of the MCP9700 is calibrated to a slope of 10mV/°C and has a DC offset of 500mV. This offset allows reading negative temperatures without the need for a negative supply. The MCP9700 is packaged in a space saving 5-pin SC-70 package, making it ideal for space-critical and low-cost applications.
- Number of Temperature Monitors: 1
- Linear Temperature Slope: 10mV/°C
- ±4°C Accuracy from 0°C to +70°C
- Temperature Range: -40°C to +150°C
- -4°C/+6°C Accuracy from -40°C to +150°C
- Very low Operating Current: 12µA (max)
- Typical Supply Current: 6uA
- Operates from 2.3V to 5.5V
- No external Components Required
- Space-saving SC-70 Package
- Hard Disk Drives and Other PC Peripherals
- Entertainment Systems
- Home Appliance
- Office Equipment
- Battery Packs and Portable Equipment
- General Purpose Temperature Monitoring
Sensor Transfer Function:
VOUT = TC X TA + V0°C
- TA = Ambient Temperature
- VOUT = Sensor Output Voltage
- V0°C = Sensor Output Voltage at 0°C
- TC = Temperature Coefficient
Scaled Temperature Coefficients:
The MCP9700 uses an internal diode to measure temperature. The diode's electrical characteristic has a temperature coefficient that provides a change in voltage based on the relative ambient temperature from -40°C to 150°C. The change in voltage is scaled to a temperature coefficient of 10.0mV/°C (typical). The output voltage at 0°C is also scaled to 500mV (typical). The MCP9700 provides a 1°C/bit resolution for an 8-bit ADC with a reference voltage of 2.5V and 5V, respectively. The MCP9700 outputs 0.1°C/bit for a 12-bit ADC with 4.096V reference.
Shutdown Using Microcontroller I/O Pin
The 6 μA (typical) low operating current of the MCP9700 makes it ideal for battery-powered applications. However, for applications that require a tighter current budget, this device can be powered using a microcontroller Input/Output (I/O) pin. The I/O pin can be toggled to shut down the device. In such applications, the microcontroller internal digital switching noise is emitted to the MCP9700 as power supply noise. However, this switching noise compromises measurement accuracy, i.e., a decoupling capacitor and series resistor will be necessary to filter out this switching noise.
The MCP9700 accuracy can be improved by performing a system calibration at a specific temperature. For example, calibrating the system at +25°C ambient improves the measurement accuracy to a ±0.5°C (typical) from 0°C to +70°C, as shown below. Therefore, when measuring relative temperature change, this family measures temperature with higher accuracy.