• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 45 subscribers
  • Views 498 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS1220EVM: ads1220

otto fest68
Prodigy 30 points
Part Number: ADS1220EVM
Other Parts Discussed in Thread: ADS1220, , ADS124S08, TIPD164, ADS1248, ADS124S08EVM

  I have to design the ads1220 basic(in ~1.5 In^2 total space) with an LDO for 3.3V from 5V and needed caps, resistor and a 8 position DIP sw. to select sensor/signal. To save time???, I copied the demo EVM assuming has all parts to test the proto and found out  that my eval kit (s/n?:4422100015?) doesn't match the schematic (file ads1x20evm-pw.schDoc) such as many parts on sch. & pcb are NOT used or populated for example : WHY R29 is used when R3 is NOT used?........is pin 8(REFN0) of 1220 left floating w/R29 as an antenna??........I have to use the 1220 to monitor RTDs,TC,SG,Th,mV, mA,etc using the selector dip switch. in other words, before I design the pcb I have to  make sure ALL functions of 1220 work with MINIMUM # of components.

can someone please correct me if I'm wrong and tell me the MINIMUM parts needed to use ALL functions(as selected by switch) ?............

thanks Jose Jimenez(OFEST)

  • 0
    TI__Guru** 113765 points

    Hi Jose,

    The ADS1220EVM was a proof-of-concept vehicle for various potential sensor input.  For the actual sensor input some assumptions were made as to which combinations would be appropriate when the EVM were first plugged in.  In many cases 0 ohm resistors were used to make various connections and options.  For example, you can use the external reference without R3 by making connections through J4.  This would appear to be a floating signal line, but note that a 100mil shorting jumper can be easily connected between pins 9 and 7 on J4 to make a connection to AGND. 

    You might ask why we did not make that a direct connection to AGND in the first place, or possibly use a switch?  Well, switches are expensive and can force a design in a less than desirable layout.  Also, it is possible to make a high-side reference using the ADS1220, so we didn't want to lock that pin strictly to AGND.

    In the end, you could use the ADS1220EVM as a model, but I think it would be much better to design a specific system specifically for a multi sensor input.  Eventually we will develop a new EVM design for the ADS1220 that may be more suitable for the type of application you desire.  This is still in the design stage and we do not have a prototype EVM at this time.

    Best regards,
    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 30 points

    thanks Bob! got it!

    I'm short in time to experiment at this point. anyplace I can find specific connections and values of parts for TC, RTD, TH, SG, SSTD(diode), mV &mA? I can do the switching via a 8 position switch and the configuration via SPI. end result: field configurable by user via switch and serial port for any sensor

    best  regards

  • 0 in reply to otto fest68
    TI__Guru** 113765 points

    Hi Jose,

    I would suggest taking a look at TIPD164 which is a design geared to the ADS1248, but it uses pretty much all the inputs you desire.  You could take portions of this schematic and determine how best to connect them to the 4 input channels of the ADS1220, or you could use this circuit with the ADS1248.  We also have a pretty new device which is the ADS124S08 and is an upgrade to the ADS1248 and could be easily substituted in this design as well.  You may also want to take a look at the ADS124S08EVM for comparison.

    Best regards,

    Bob B