Measuring Temperature with the

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Step 10. Set the ADC Input for TEMP+ to TEMP-

Set the polarity flipper back to normal by clearing the POL bit in the ADC register. 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 11. Measure V_BE2 using the ADC

The V_BE2 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_BE2 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 VBE2 for later calculation.

Step 12. Set the ADC Input for V_R2

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 13. Measure V_R2 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 VR2 for later calculation.

Step 14. Set the Current Source for I₃ (64µA)

Set the current source for I₃ by setting the IVAL[1:0] bits to 0x10 in the TEMP_CTRL register.

Step 15. Set the ADC Input for TEMP+ to TEMP-

Set the polarity flipper back to normal by clearing the POL bit in the ADC register. 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 16. Measure V_BE3 Using the ADC

The V_BE3 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_BE3 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 VBE3 for later calculation.

Step 17. Set the ADC Input for V_R3

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 18. Measure V_R3 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 VR3 for later calculation.

Step 19. Set the Current Source for I₄ (120µA)

Set the current source for I₄ by setting the IVAL[1:0] bits to 0x11 in the TEMP_CTRL register.

Step 20. Set the ADC Input for TEMP+ to TEMP-

Set the polarity flipper back to normal by clearing the POL bit in the ADC register. 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 21. Measure V_BE4 Using the ADC

The V_BE4 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_BE4 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 VBE4 for later calculation.

Step 22. Set the ADC Input for V_R4

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 23. Measure V_R4 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 VR4 for later calculation.

Step 24. Calculate the Temperature

The temperature is calculated using the formula in Equation 1 above. The equation can be simplified by multiplying and dividing the constants in advance. The constant is applied to Equation 2 shown below.


Equation 2. Simplified four-current temperature measurement equation.

Four-Current Method Example Using Real Data

The temperature was measured on an evaluation (EV) kit at room temperature using the procedure above with the following results.

For I1 4µA	NVBE1 = 0x81AF	NVR1 = 0x0350
For I2 60µA	NVBE2 = 0x9048	NVR2 = 0x32D4
For I3 64µA	NVBE3 = 0x90A5	NVR3 = 0x3629
For I4 120µA	NVBE4 = 0x93E2	NVR4 = 0x615c

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