Measuring Temperature with the

文章摘要：16 = Number of ADC steps for MAX1358 16-bit ADCTo convert the measured temperature in Kelvin to degrees Celsius, the following formula is used:°C = K - 273.15Procedure Using the Internal TransistorThe procedure for measuring the voltages across the internal transistor and internal resistor applies a

Measuring Temperature with the,标签：模拟电子技术基础,模拟电子电路,http://www.88dzw.com
16 = Number of ADC steps for MAX1358 16-bit ADC

To convert the measured temperature in Kelvin to degrees Celsius, the following formula is used:

°C = K - 273.15

Procedure Using the Internal Transistor

The procedure for measuring the voltages across the internal transistor and internal resistor applies a current from the current source, and measures the resulting V_BE and V_R.

Step 1. Enable the Reference and ADC

Enable the internal 1.251V reference and the reference buffer with a gain of 1.0 by setting REFV[1:0] bits to 0x01 in the REF_SDC register.

Enable the ADC by setting the ADCE bit in the ADC register. The internal reference and ADC are enabled. Note: The ADC is set with the default parameters of unipolar, normal polarity, single conversion, internal reference, unity gain, 10 samples per second, and normal conversion.

Step 2. Calibrate the ADC

Set the ADC conversion mode to Self Offset and Gain Calibration by setting the Mode[2:0] bits to 0x07 in the ADC register. Start an ADC conversion by setting the STRT bit in the ADC register. The ADC is now calibrated. The Mode[2:0] bits in the ADC register are automatically cleared. This returns the ADC to normal operation.

Step 3. Set the Current Source for the Internal Temperature Sensor

Set the current source for the internal temperature sensor by setting the IMUX[1:0] bits to 0x01 in the TEMP_CTRL register.

Step 4. Set the Current Source for I₁ (4µA)

Set the current source for I₁ by setting the IVAL[1:0] bits to 0x00 in the TEMP_CTRL register.

Step 5. Set the ADC Input for TEMP+ to TEMP-

Set the ADC positive input multiplexer for TEMP+ by setting MUXP[3:0] to 0x07 in the MUX register. Set the ADC negative multiplexer for TEMP- by setting MUXN[3:0] to 0x00 in the MUX register.

Step 6. Measure V_BE1 using the ADC

The V_BE1 voltage is measured from the TEMP+ to the TEMP- inputs to the ADC. The ADC is already configured and only needs to convert to get the resulting V_BE1 voltage. To start the ADC conversion, set the STRT bit in the ADC register. The ADC will do a conversion and the result will be in the DATA register. Read the DATA register value and save as a 16-bit integer named VBE1 for later calculation.

Step 7. Set the ADC Input for V_R1

Set the ADC positive input multiplexer for AGND by setting MUXP[3:0] to 0x09 in the MUX register. Set the ADC negative multiplexer for TEMP- by setting MUXN[3:0] to 0x00 in the MUX register (same as step 5). To measure the TEMP- input relative to AGND, the polarity flipper bit is used. Set the POL bit in the ADC register. The ADC is now setup with TEMP- as its positive input and AGND as its negative input.

Step 8. Measure V_R1 using the ADC

To start the ADC conversion, set the STRT bit in the ADC register. The ADC will do a conversion and the result will be in the DATA register. Read the DATA register value and save as a 16-bit integer named VR1 for later calculation.

Step 9. Set the Current Source for I₂ (60µA)

Set the current source for I₂ by setting the IVAL[1:0] bits to 0x01 in the TEMP_CTRL register.

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