Temperature Sensor
Introduction
A temperature sensor is integrated in the device to measure the chip die temperature. As one of the analog input signals of SNSADC, temperature signals can be converted into digital signals by using the SNSADC. Users can obtain the temperature value according to the conversion formula. It also uses temperature sensors to adjust RF parameters inside the chip
Main Features
- Integrated into the SNSADC module and serves as one of the SNSADC input signals.
- Measures the die temperature to check whether it is greater than or equal to the operating temperature of the device.
- Temperature measurement range: -40°C to + 105°C
- The measurement accuracy at normal temperature is 1°C to 2°C, and the maximum error at high or low temperature is 5°C.
Functional Description
The temperature sensor converts the temperature signals inside the chip into voltage. The SNSADC module can be used to sample the converted voltage signals and then calculate the temperature value through the conversion formula.
Acquisition Parameter Configuration
In order to sample the voltage signals from the temperature sensor, SNSADC needs to be configured to single-ended mode: Temperature sensor should be set as input source of channel N, and enable temperature sensor by setting the bit of SNSADC_CFG.TEMP_EN. Set SNSADC as internal reference source, and select 0p8 for reference value. A 1 MHz clock is recommended for sampling clock.
Conversion formula
After getting some code from the SNSADC, you can average the code and then convert the average code value into an actual temperature value according to the following conversion formula:
In the formula above, adc_slope is the slope value corresponding to the reference voltage gear of SNSADC. The slope value corresponds to 0p8 gear. The adc_temp is the offset value after calibration based on normal temperature and the Temp_ref is the environment temperature value when calibrated.
These parameters are the calibration parameters of the chip and are saved in OTP.
Measuring Internal Temperature
The device has a built-in temperature sensor module, and the measurement range is from -40°C to 105°C. The temperature sensor converts the internal temperature of the chip into a voltage value and outputs it to the ADC for sample and conversion. After temperature calibration, the raw_data obtained by ADC can be converted into an actual temperature value.
If users want to measure the internal temperature of the chip, it is necessary to configure the SNSADC_CFG.CH_N field as 0xD (temperature sensor as input of channel N), and select the internal reference voltage of 0.8 V.
Registers
See the description of register SNSADC_CFG (SNSADC Configuration Register) of SNSADC.
