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Opamp suggesting for buffer configuration

d_zero
Genius 4865 points
Other Parts Discussed in Thread: TLV9001, TLV521

Dear *,

can you suggest or recommend low price newer opamp part for buffer configuration?

it should work with 3.3V supply.  The input we will have a resistor divider to bring sensed voltage of 24V to 3V, and the output of opamp will be connected to  adc input of MSP430FR2353TRHA.

Bes Regards,

David.

  • 0
    Guru 318050 points

    Use the search function to find 3.3 V opamps with rail-to-rail inputs. Use the TLV9001, or the TLV521 if need low power but no speed.

  • Former Member
    0 Former Member

    Hi David,

    I concur with Clemens' response.  Please let us know if there are any other design needs or specifications of concern.

    You will need a rail-to-rail input amplifier as noted.  If you want extra accuracy, make sure to pick an amplifier that does not have a degraded input offset voltage near the V+ rail.  We can consider this in more detail if needed.

    Regards,
    Daniel

  • 0 in reply to Former Member
    Genius 4865 points

    Dear Daniel and Clemens,

    what about the unity GBW ?

    I want to construct a buffer driver for MSP430 SAR ADC, and i was going through this training:

    and used Analog Engineer's calculator and got required bandwidth of 27.7MHz

    But i'm not shore about the Acquisition time value and thus i used the tSettling value from the MSP430 datasheet ?

    Best Regards,

    David.

  • 0 in reply to d_zero
    Guru 318050 points

    The acquisition time is the time between the start of two consecutive ADC measurements. The tSample value plus the ADC conversion time is a lower bound. You should use the maximum time after which you actually need to be able to detect a change in the input voltage.

  • Former Member
    0 Former Member in reply to d_zero

    Hi David,

    Your ADC will have a throughput, which is the measure of how many samples can be handled per second.  For a SAR ADC, each sample collection consists of two phases: acquisition and conversion.  Together, these two determine your sample rate and, hence, throughput.

    There is a great presentation on how this works and how you can figure out the acquisition time. The part most relevant to your question is toward the end of the presentation.  However, you may also find the rest of the presentation useful.  Furthermore, the rest of the videos in the series walk through the process of picking an amp, refining the input filter values, using the tool, and much more.  It is very helpful for this sort of thing in my opinion.

    Regards,
    Daniel