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TLV07: any concern for this voltage sensing circuit?

Aki Li
Expert 8265 points
Part Number: TLV07
Other Parts Discussed in Thread: OPA333

Customer would like to use TLV07 to sense the DC voltage of 38V~60V with the below circuits. Could you please help check whether there any any concerns? Thank you.

  • 0
    Guru 140200 points

    Hi Aki,

    like this?

    aki_tlv07.TSC

    Hhm, doesn't really look good :-(

    I don't understand this circuit. What is the diode D1 for? And what is the purpose of the voltage divider R2, R5 and R7?

    Kai

  • 0 in reply to kai klaas69
    TI__Expert 8265 points

    Hi Kai,

    The main reason is that the DC voltage(38V~60V) and TLV07 have different grounds. But I am also confused by the purpose of the diode D1. 

  • 0 in reply to Aki Li
    TI__Guru* 93105 points

    Hi Aki,

    I agree with Kai's questioning of the circuit. It doesn't appear to be completely correct. Simulation shows that the TLV07 output is being driven into the negative output rail, and increasing the input voltage is just moving the output more positive by a small amount. The large offset change in VM2 in the TINA diagram below indicates a problem. When I replace the TLV07 with a RIRO op amp such as the OPA333 I see that VM2 stays constant as expected.  

    I suggest the customer give some more thought to what they need to accomplish with the design and make changes accordingly. Once they have a fully functioning circuit we can assist with any questions they may have.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

    TLV07_Sense_01.TSC