# Thread: Temperature Sensor of BGT24MTR11 -- wrong transfer function equation

1. ## Temperature Sensor of BGT24MTR11 -- wrong transfer function equation

Hi all，

In the document "BGT24MTR11 Appllication Note AN305 User 's Guide to BGT24MTR11 24 GHz Radar", page 13, figure 8 shows the transfer characteristics of temperature sensor.
But the equation of Temperature and Vtemp does not match the figure, the transfer function is:
T/°C = 0.22*(Vtemp/mV) - 289
when the Vtemp=500mV, T should reads 0.22*500-289=-179°C, but in the figure it reads around 35°C. Is there a correct equation?

BTW, is it possible to use the VTEMP signal to make a stable VTUNE input, just like the BGT24LTR11?

Thanks,
Jhon

2. Thank you for reporting this. Yes, the offset in the formula for the trend line should be in the range of 76..78. You can use the temperature level in he control loop for the tuning voltage input. Refer to page 6 in the AN305.

3. Thank you berbra, with offset 77, I can draw a line just like figure 8.
But it's the a formula between the 'delta Vtemp' and temperature. What does the word 'delta' mean? How can I get the formula between the true Vtemp and temperature?

4. Originally Posted by berbra
Thank you for reporting this. Yes, the offset in the formula for the trend line should be in the range of 76..78. You can use the temperature level in he control loop for the tuning voltage input. Refer to page 6 in the AN305.
It seems that deltaVtemp in figure 8 is the subtraction of VTemp and some Vref. According to table 13 of BGT24MTR12 datasheet, there are two ref voltage: Vref_tx and Vref_lo, is one of these 2 signals used to make delataVtemp?

5. Hi Jhon,

we have double-checked the transfer function and it seems to be outdated.
Please calibrate the sensor according to the attached pdf to get the accuracy given in the datasheet.

6. Originally Posted by dagern
Hi Jhon,

we have double-checked the transfer function and it seems to be outdated.
Please calibrate the sensor according to the attached pdf to get the accuracy given in the datasheet.
https://www.infineonforums.com/threa...-BGT24LTR11N16

Thanks!