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AD590 temperature sensor

Hi Team,
A few days back, I posted a thread, but till now I don't get any response so I'm posting my thread here again
I am trying to make a temperature sensor using AD590 from a +5V supply.
The V+ pin of AD590 will be connected to the +5V and the V- pin is connected to a 1K resistor and the voltage across the 1K (single-ended) is taken to a buffer using op-amp ADA4805-2.
The op-amp is operated at a +3.3V. I hope the circuit will work fine.
Also, can I use the same circuit set up to measure the temperature if I simply replace the AD590 with a diode like 1N4148?.
The unused op-amp is used as a voltage monitor like in the below circuit. Will it arise any problem with the design?.

  • Hi, 

    First apologies for missing your thread. Then can you share your intended application? Where does Temp_out go to? When you plan to replace the AD590 with a diode, do you mean as an option in this application? When will the op-am be "unused" ? Note that diodes require an excitation current to generate a PTAT voltage. We have other parts better suited if you intend to use a diode to measure temperature. 



  • Hi 
    Thank you for your reply.
    1). The Temp_out will be an analog input of my processor
    2). Yeah. I hope I can use a diode instead of AD590 in the same application without many alterations, 
    What I'm planning is the AD590 will be powered from a 5V source and there will be a shunt 1K shunt resistor.
    At 25°C, my voltage will be around 298mV.
    To use the diode, there will be another 1K resistor to provide biasing to the diode from the 5V supply, the diode will be connected in series with the 1K resistor and the output will be taken across the diode (sorry not included in the given circuit)

    The second op-amp is used as a voltage monitor. I'll be able to determine the on or off state of the regulators used.
    Just for curiosity could you please provide the details of the parts available when using the diode as a temperature sensor

  • Hi, 

    For the temperature sensor side, the AD590 connection is fine. I'm not seeing an issue now that you have explained you have the resistor in series with the diode. Just curious how you plan to choose between them - are you adding a switch or jumper options? The parts I mentioned that you can look into if you intend to measure temperature with diodes are the LTC2997 and the LTC298x family.

    For the voltage monitor, I'm not sure how it connects to the next stage where it determines the state of the regulators but I think you need to review because it looks like you are already over  the ADA4805-2's input common mode voltage range (at 3V supply, max is spec is 2V). If you have a 5V supply for the diode anyway, you can use that to supply the ADA4805-2 and you the common mode voltage won't be an issue anymore (at 5V supply, max input common mode is 4V).