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OPA2333P: Voltage monitor

Shibin Varghese
Prodigy 185 points
Part Number: OPA2333P


Hi Team,
I want to design a voltage monitor. These voltages are generated from an LDO and a charge pump (includes both positive and negative DC voltages.)

I designed the circuit as shown.
A voltage divider is set between my +5V and -5V so that my voltage at the noninverting terminal is roughly around 2V.
The op-amp is configured like a buffer.
The net OUT is connected to an analog pin of my controller so that I can monitor any change in the supply voltage.
Will it arise any problem in my design?.
Also, If I want to connect the temperature sensors like AD590 (current output) to the unused op-amp, how can I complete my design?

  • 0
    Prodigy 185 points

    Any updates?????????????????????????????????????????

  • +1 in reply to Shibin Varghese
    TI__Guru* 77541 points

    Hi Shibin,

    Monday is our holiday, hence we had the response delay. 

    Q: Will it arise any problem in my design? 

    Your design may work, but I have some concerns, since I do not know the requirements in monitoring both +5V and -5V in a single circuit (unless the purpose to save one op amp). 

    If both +5Vdc and -5Vdc are stiff voltage source, then the output of the signal should be measured approx. 2.5V. In reality, both +5Vdc and -5Vdc changes as a function of time, load conditions etc.. There are voltage ripple riding on both regulators. 

    In the simulation below, I simulated +5Vdc and -5Vdc with a different ripple voltage (up too 200mV). As you may see, if it is difficult to tell the conditions of 5V and -5V individually. If you are only interested to monitor about On or Off states in either voltage regulators, then the design will work. 


    OPA2333 E2E 06012021.TSC

    Q: Also, If I want to connect the temperature sensors like AD590 (current output) to the unused op-amp, how can I complete my design?

    It looks like that AD590 is a current source with nominal 298.2uA @25C (273.15+25 K=298.15K), and linear current output is 1uA/K.  

    OPA2333 with Current Sensor.TSC

    So the temperature sensor will drive a fix resistor load, say 1kOhm. Since IS1 (AD590) is varied from 218.2K to 423.2K (-55C to 150C), the output should be close to be linear specified by the sensor datasheet. I did not incorporate gain in the attached schematic. You have an option to increase 1kOhm accordingly or increase the op amp's gains. 

    If you have additional questions, please let us know. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Prodigy 185 points

    Hi Raymond,
    Thank you for your reply.
    True, we cannot measure the +5V and -5V individually, but we can monitor the On or Off states in either voltage regulator.
    If I have to replace the AD590 power outlet with a diode like 1N4148 to measure the temperature, I think I just need to replace the AD90 with the diode in the same circuit setup. Right?. Please correct me if I'm wrong.