Hi Team.
I am designing a temperature sensor with a 10K NTC.
Attached is the schematic as per the application note SBOA323A.
My required output voltage is from 0.5V to 3.2V.
The op-amp is supplied from a 3.3V voltage source.
My temperature range is 0°C to 50°C.
According to the datasheet of the NTC.
The resistance at 0°C is 26 783Ω to 27 913Ω
The resistance at 50°C is 4079.2Ω to 4237.3Ω.
Is my design correct?.
Hello Shibin,
Here is a TINA-TI circuit for your design:TLV9052_NTC_Shibin.TSC
I simulated the circuit using your component values, but the amplifier output quickly saturated. I recalculated the component values and found the required gain to be 1.864V/V vs the 3.917V/V you were using. Additionally, it is necessary to change the ratio of R2 and R4 to get the desired offset on the output.
The TINA file I attached includes these changes.
In the case of the simulation, I swept from 4.158kOhm to 27.35kOhm representing 50C and 0C respectively. I do not have a NTC model for your particular thermistor, so I was forced to sweep across resistance. Note, the output looks non-linear, but this is due the thermistor possessing a nonlinear resistance vs temperature curve. You are welcome to replace RNTC with the specific thermistor you intend to use to verify linear operation.
Here is your output(red) and input(green)
Vo at 50C(4.158kOhm) = 3.15V
Vo at 0C(27.35kOhm) = 464.8mV
Feel free to modify the component values to get standard values.
Please let me know if you have any questions.
Best,
Jacob
