Temperature Sensor

Introduction

A temperature sensor is integrated in GR5526 to measure the die temperature inside the chip. As one of the analog input signals of SADC, temperature signals can be converted into digital signals by using the SADC. You can obtain the temperature value according to the conversion formula. GR5526 also uses temperature sensors to adjust RF parameters inside the chip.

Main Features

Integrated into the SADC module and serves as one of the SADC 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 + 80°C.
The measurement accuracy at normal temperature is 1~2°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 SADC module inside the chip 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, SADC needs to be configured to single-ended mode: channel N should be set as ADC_INPUT_SRC_TMP, and enable temperature sensor by setting the bit of en_temp_sense. Set SADC 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 SADC, you can average the code and then convert the average code value into an actual temperature value according to the following conversion formula:

T e m p e r a t u r e v a l u e = [(a v e r a g e_c o d e - a d c_t e m p) / (a d c_s l o p e * 2)] / (0.00175) + T e m p_r e f

In the formula above, adc_slope is the slope value corresponding to the reference voltage gear of SADC. 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 eFuse.

Measuring Internal Temperature

GR5526 has a temperature sensor module inside, and the measurement range is from -40°C to 80°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 ADC converts the digital value into an actual temperature value.

图 145 Schematic diagram of temperature measurement

If users want to measure the internal temperature of the chip, it is necessary to configure the N channel of the ADC as ADC_INPUT_SRC_TMP, and select the internal reference voltage of 0.8 V. The calibration formula is as follows:

temperature = (code - temp_25_offset) / slope / (- 0.00175) + tem_25

Where, temp_25 represents an ambient temperature of 25°C; temp_25_offset represents ADC raw value at 25°C ambient temperature; slope represents the calibrated slope value of the internal 0.8 V reference voltage; -0.00175 represents the amplification factor for the slope when used to measure temperature. In general, the output voltage decreases by a typical value of 1.863 mV for every 1 degree increase in temperature. The typical value of the voltage is 807.5 mV at -40°C and 583.9 mV at 80°C.

Registers

See the description of register CFG (Sense SADC Configuration Register) of SADC.

Electrical Specifications

表 744 Electrical specifications
Parameter	Symbol	Min.	Typ.	Max.	Unit
Temperature sensor range	Temp_range	-40		80	°C
Temperature sensor accuracy	Temp_accuracy	-10		10	°C
Temperature sensor resolution	Temp_resolution		1.19		°C
Sample stability at constant temperature	Temp_stability	-1.19		1.19	°C
Voltage slope per degree	Vol_degree	-1.871	-1.863	-1.843	mV
Voltage of -40 degree	Vol_-40	807.5	807.5	809.9	mV
Voltage of 80 degree	Vol₈₀	581.5	581.5	583.9	mV