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  • TI Thinks Resolved

LPV7215: Does this Low voltage and low power comparator generate Square wave @ 1.8v..?

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Replies: 10

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Part Number: LPV7215

Hi
    I have one question regarding LVP7215M, Does this really generate Square wave @ voltage 1.8 with 580nA..?

   I would like to design 1.8v battery based wave form generator with combination of LC and R.

   if this will not suite my purpose, kindly suggest if any different device fulfill my needs as well.


  FYI:  I don't have a simulator for this chip.

thanks
Mani

  • Hi Ranganathan,

    of course, you must add the load currents through the feedback resistances.

    Can you show a schematic of your circuit?

    Kai
  • Hello Mani,

    The comparator itself will draw 580nA steady-state, but there is also the external resistor dividers and charging current for the capacitor that will add to the supply budget.

    You can make the resistors large, but you have to watch making the capacitor too small - or you have to account for stray capacitance.

    Comparators also draw peak currents when the output transitions. These peak currents usually occur while the output is moving and they can be many times the quiescent current. This current gets averaged by the bypass cap, but the result is a rising average supply current vs output frequency.

    What is the frequency range you are interested in? The faster you go, the more current that will be needed for the faster prop delay spec.

    We have newer devices with even lower supply currents, such as the TLV7031(330nA)  or even the TLV3691 (70nA). These two both have SPICE models.

    But your choices are dominated by the required propagation delay required to achieve your frequencies of interest.

    Please see the following appnotes and TI Precision labs presentation:

     Relaxation oscillator circuit  Appnote TINA file: http://www.ti.com/lit/mo/sbomao3/sbomao3.zip

     2103 - Comparator Applications 3.pdf (see Maximum Toggle Frequency - Page 16)

    Regards,

    Paul Grohe

    TI Comparators (CMPS) Applications Group

  • In reply to Paul Grohe:

    Hi Kai and Paul,
    Thank a lot for your responses.
    Ok, I will try to simulate TLV7031 & TLV3691 and I will build my design based on the results soon.

    FYI: My design expecting the frequency range from 10KHz to 500KHz. (at worst case 1MHz)

    My major concern are really these comparators will work with 1.8 volt or not because all reference circuit (from TI) using either 3v or 5v. Kindly confirm and if you have any reference design schematic for 1.8v kindly share with me.

    I will try to simulate these two comparators and and come back to you soon.

    Once again thanks.
    mani
  • In reply to RANGANATHAN MANIKANDAN:

    Hi Ranganathan,

    a maximum frequency of about 100kHz seems realistic with the TLV7031:

    ranganathan.TSC

    Kai

  • In reply to kai klaas69:

    Hi Kai,
    You are really a great. Thanks for your deep support.
    I will go for my design then.

    Thank a LOT for your extensive support regarding my question.
    I'm really happy about your file, simulation result and your reply.

    Once again thanks.
    Mani
  • In reply to RANGANATHAN MANIKANDAN:

    Mani

    For the upper range of your frequency requirements you will need to switch to our faster  version of the tlv7031 which is the TLV7011. This comparator is approximately 10x faster and should get you to your 1MHz max target. Operating at 1.8v will not be a problem and the quiescent is around 5uA in idle state. Models for this comparator are also available.

    Chuck

  • In reply to RANGANATHAN MANIKANDAN:

    Hi Kai,

        I have simulated your file, but i can see new scenario.. the waveform swing top and bottom..

       Is that real scenario.. (or) for only simulation.

    please find the screen print for your reference.

    thanks and regards,

    Mani

  • In reply to RANGANATHAN MANIKANDAN:

  • In reply to RANGANATHAN MANIKANDAN:

  • In reply to RANGANATHAN MANIKANDAN:

    Hi Ranganathan,

    change the scope settings:

    Also set "Mode" to "Normal".

    Kai

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