SLASEC8B February 2017 – January 2019 PGA460-Q1
The PGA460-Q1 device has an on-chip temperature sensor and a dedicated temperature data path for accurate temperature measurement. The output value is provided as an unsigned 8-bit number from –40°C to +125°C. The temperature sensor measurement can be used to adjust the variation of the transducer performance as the ambient temperature changes. The temperature measurement's sample and conversion time requires at least 100 us after the temperature measurement command is issued. Do not send other commands during this time to allow the temperature value to properly update.
The output of the temperature digital data path can be read by using the time-command interface of the UART interface. The value provided is related to the measured temperature as shown in Equation 7.
Because the output value of T(VAL) after the calculation can result in a decimal number, the value is rounded-up to the closest integer value.
The temperature digital data path consists of a 16-sample averager and a scaling block as shown in Figure 41. The 16-sample averaging block averages 16 temperature measurements arriving at a rate of 1 sample/µs into one result to remove temperature measurement variations. The scaling block is used to adjust the Gain and the offset parameter to better calibrate the temperature sensor. These two parameters are programmed using TEMP_GAIN and TEMP_OFF bits in the TEMP_TRIM EEPROM register.
Before compensation (TEMP_GAIN bit set to 0, TEMP_OFF bit set to 0), T(VAL) is same the value converted by the ADC. As previously above, the user can compensate for variations in operating conditions (VPWR), board design, and configuration of the device by performing a two-temperature measurement and trim. After compensation, T(VAL) can be converted to an absolute temperature using Equation 7. As the VPWR is increased, power dissipation increases and the internal die temperature can be different from the ambient temperature. The temperature sensor always indicates the die temperature.
Without calibrating TEMP_GAIN and TEMP_OFF, the ambient temperature can be approximated from the die temperature reading using Equation 8