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TIPD151 reference design

aseok tag
Intellectual 290 points
Other Parts Discussed in Thread: ADS1258, TIPD151Hello For some mobile application , i should change this reference design according to this specs : - embedded system with storing capabilities . - 8 channel differential input at 30KHZ frequency . - 24 bit resolution - input voltage amplitude of 5 volts . Thanks .
  • 0
    TI__Guru** 112635 points

    Hi Aseok,

    The TIPD you are referring to uses a SAR ADC, and to get higher resolution you will need to use a Delta-Sigma converter.  So you will need to take that into account as usually you can't just take one design and change the ADC.

    You may want to take a look at the ADS1258, as it comes very close to what you need.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Intellectual 290 points
    Thanks , is 24 bit resolution really achievable ? how ?
  • 0 in reply to aseok tag
    TI__Guru** 112635 points

    Hi Aseok,

    24-bit as specified by the datasheet refers to the smallest measurable unit over the reference range of the device.  The problem is noise, linearity, offset and gain errors within the system.  You can improve the results by additional filtering (such as averaging), but at some point drift will start to factor into the results.

    Now to answer your question, in most cases you will not achieve the ability to make a measurement to within 0.000005% of the input voltage, which is what you are asking for when measuring down to 1 part in 2^24 bits (16777216).  That said, you may be able to measure a smaller range (LSB size) with higher precision using gain of an internal PGA.  Without getting into a lot of theory, let me just say that you may not need to have 24-bits to get the desired end result.

    You can also spend a lot of effort on getting lower noise only to find that the sensor output is not able to achieve the higher resolution anyway.  You really need to spend time understanding your whole system and what is affecting the system prior to the ADC, and then matching the ADC to the rest of the system.

    The delta-sigma devices use a noise shaping modulator which shapes the quantization noise into the higher frequencies.  The digital filter is similar to a low pass filter to remove the higher frequency noise from the result.  Increasing the data rate lowers the decimation and noise starts to become a factor as the digital filter bandwidth increases.  This means I may be able to achieve 24 noise free bits at 1sps but this may reduce to 16 bits at 30ksps.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Intellectual 290 points

    Hello

    I have a problem opening the .sch & .pcb files of TIPD151 reference design with altium designer or altium designer viewer , please help .

    Can i use cadsoft eagle to open .sch (schematic) file ? how ?

    Thanks .