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TLV1851: Voltagemeter

Bertrand Coucke
Prodigy 30 points

Part Number: TLV1851
Other Parts Discussed in Thread: TLV1821

Dear poeple

I have a question related about the TLV1851. As shown in my picture I want to use it as a voltagemeter.

If the voltage is lower than the reference voltage the output needs to be HIGH.

I want to feed the OPAMP with 3.3V. So that it can directly be connected to my ESP32.

The max input would be 20V.

Does this word as drawn in my picture?

  • 0
    TI__Guru 66706 points

    Hello Bertrand,

    Yes. This will work, but the voltage from the wiper on the positive input and the reference cannot go more than 3.3V.

    What is your expected input voltage range? There may be better devices to use.

  • 0
    Prodigy 30 points

    0-20V in is used as a comparator so of the voltage is below than the potentiometer there Will be a high output of 3,3V

  • 0 in reply to Bertrand Coucke
    TI__Guru 66706 points

    Hello Bertrand,

    What is the expected input  voltage range on the "Input" (inverting) node?

    What is the expected maximum voltage on the positive input? Are you planning to turn the pot to maximum?

    With a 3.3V supply, the maximum input voltage to the comparator is 3.3V. The internal ESD diodes will clamp the inputs to the 3.3V supply if you exceed 3.3V on the inputs.

    Ideally, you should be using a open-collector/drain output, where you can set the output "high" voltage (VOH) regardless of the comparator supply voltage.

    For example, you could use a TLV1821 (open collector output) and power it off the 20V supply, and pull-up the output to 3.3V to interface to your digital logic. That would allow you to apply the full 0 to 20V to the inputs, but the output will always be 0 to 3.3V.

  • 0 in reply to Paul Grohe
    TI__Genius 13425 points

    Hey Bertrand,

    Feel free to reopen this post if you have any further updates.