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Original question:

ADS122U04: Common Power Supply source for Analog as well as Digital power supply input pins AVDD and DVDD

ADS122U04: ADS122U04

Milind Risbud
Prodigy 150 points
Part Number: ADS122U04

Hello Bob,
Thank you for replying to my earlier query regarding ADS122U04 interfacing with RTD PT100.
In the same project I also need to use ADS122U04 for measuring Engine Oil pressure (in heavy vehicles) -
using MEAS make M5100 series pressure transducer (either having 4 to 20mA output OR 0-5Vdc output - yet to be decided).
I am unable to find an application note to help me in designing the interfacing circuit between such a pressure transducer and ADS122U04.
I also need your suggestion on which type of pressure transducer should I use i.e. the one having 4 to 20mA output OR 0-5Vdc output ?
The other details are as follows:-

a) I shall be using the WQFN (3mmx3mm) package of  ADS122U04.

b) ADS122U04 and associated circuitry will be populated on a very small PCB (15mmx20mm) that shall be fitted in a very small enclosure that will be fitted on the  pressure transducer.

c) This above mentioned module shall transmit the 24Bit results of AtoD conversions over long distance (for processing purpose) using UART interface of  ADS122U04. 

 

Thank you,

Regards,

Milind Risbud.

 

  • 0
    TI__Guru** 112895 points

    Hi Milind,

    Regardless of whether you use the output of a 4-20mA or the 0-5V, the measurement will be a voltage measurement.  In the case of the 4-20mA you pass the current through a shunt resistor (100 Ohms for example) and measure the voltage across the shunt.  The measurement itself becomes a single-ended voltage measurement and would require that the PGA be disabled and bypassed for this use case.

    We don't have a specific use case for a pressure sensor, but for the voltage and current measurement you can take a look at the ADS122U04EVM user's guide.  Review the connections on page 27 in section 5.1.4.

    There is a TI design for the ADS122U04 that has a current measurement circuit in an isolated design.  The measurement circuit for the input could be used as an example in measuring the current from 4-20mA output.

    https://www.ti.com/tool/TIDA-010048

    Best regards,

    Bob B