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LDC1312: Resolution and Conversion Interval

Ke Quan Tok
Prodigy 210 points
Part Number: LDC1312
Other Parts Discussed in Thread: LDC1612

Tool/software:

Hi BU,

I am John Tok, TI FAE based in Singapore who is currently supporting for ASMPT.

There is a question from customer regarding LDC1312 and LDC1612. By referring to LDC1312 datasheet, it mentions the conversion interval is configurable from 3.2 us to 26.2 ms, same goes to LDC1612. Hence, customer is asking what the difference in terms of resolution is corresponds to the specific conversion interval.

E.g. Is LCD1312 has better resolution than LCD1612 when both are configured to 3.2 us conversion interval? If yes, by how much?

Can you help to advise on how to differentiate in this scenario? Thanks. 

Regards,

John Tok

  • 0
    TI__Mastermind 18545 points

    Hello John, 

    When comparing the resolution of the LDC1612 to the LDC1312, the LDC1612 device will have a higher resolution as it reports the data as a 28-bit value while the LDC1312 reports a 12-bit value. 

    For more comparisons between the two devices, table 3-1 of the LDC Device Selection Guide (Rev. D) can be helpful: 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Prodigy 210 points

    Hi Justin,

    Thanks for the reply. Customer is aware of LDC1612 has higher resolution than LDC1312. 

    However, both datasheets mentioned "Longer conversion intervals have higher measurement resolution". In this case, how can we know what exact value of resolution is when the conversion interval is 3.2 us? Any calculations are provided to determine the resolution value from conversion interval? 

    Thanks.

    Regards,

    John Tok

  • 0 in reply to Ke Quan Tok
    TI__Prodigy 210 points

    Hi Justin,

    This is the datasheet from LDC1612. It is mentioned in your table that the output L measurement resolution is 28 bits for LDC1612. But why in LDC1612 datasheet, it will use 16 bits to calculate the conversion interval? 

    Customer would like to know what is the difference between LDC1312 and LDC1612 in this section. Could you help to clarify further?

    Regards,

    John Tok

  • +1 in reply to Ke Quan Tok
    TI__Mastermind 18545 points

    Hello John, 

    Ke Quan Tok said:
    However, both datasheets mentioned "Longer conversion intervals have higher measurement resolution". In this case, how can we know what exact value of resolution is when the conversion interval is 3.2 us? Any calculations are provided to determine the resolution value from conversion interval? 

    The overall resolution you have depends on the dynamic range of your measurement for your target motion, the noise in your environment, and the RCOUNT value chosen. If you fix your RCOUNT register setting to have a 3.2us conversion interval, then you just have to determine what the dynamic range of your data will be for the target motion and your noise or standard deviation in your measurement based on the operating environment. For axial sensing applications, you can estimate the dynamic range of your measurement using our LDC-DESIGN-TOOLS by going to the LDC131x-LDC161x_Config tab and using the 'Axial Target Movement Calculations' section: 

    Ke Quan Tok said:
    This is the datasheet from LDC1612. It is mentioned in your table that the output L measurement resolution is 28 bits for LDC1612. But why in LDC1612 datasheet, it will use 16 bits to calculate the conversion interval? 

    The data output of the LDC1612 is a 28-bit value split between two registers in the device but only one register is used to set the conversion interval as 16-bit value. 

    Ke Quan Tok said:
    Customer would like to know what is the difference between LDC1312 and LDC1612 in this section. Could you help to clarify further?

    The RCOUNT setting is similar between the two devices. They both have the same 16-bit option to set the conversion time however, the LDC1312 has diminished improvements on the resolution with RCOUNT values above 0x2000. You can find more information on setting the RCOUNT and optimizing resolution for these devices in the following app notes: 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Prodigy 210 points

    Hi Justin,

    Thanks for the clear explanation! I will get back to customer, thanks!

    Regards,
    John Tok