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Several ADS1230, one microcontroller

Gustavo Furlan
Prodigy 40 points
Other Parts Discussed in Thread: ADS1230, ADS1234, ADS1232, ADS1220

 Does TI has any design guide to wire several ADS1230 using just one microcontroller and one SPI port? What is the best way to do that?

 If the PWDN pin can be used like a chip select (active high in this case), it would solve the problem, but I don´t know the state of SCLK and DOUT pins during power down. Are they three stated?

 Well, maybe someone has a better idea.

 Thanks. 

   

  • 0
    TI__Guru** 112795 points

    Hi Gustavo,

    Unfortunately the power down shuts down the power to the analog portion and the digitial is in a low power state.  The DOUT pin is still driven.  SCLK is an input pin, but it will affect the data as the clocking will clock out the data.  A couple of methods that can be used is a decoder or GPIO pin directly connected to tri-state buffers.  You would activate the desired buffer based on the device you are attempting to read.  If you buffer both the DOUT and SCLK, you should have a pull-down resistor at the output of the SCLK buffer to limit the  transient on SCLK and prevent the ADS1230 input from floating.

    Have you considered the ADS1234?  This is a four channel device with a little bit better spec than the ADS1230.

    Best regards,

    Bob B 

  • 0 in reply to Bob Benjamin
    Prodigy 40 points

      Hi Bob, first of all thanks a lot for your help.

     A tristate buffer sounds like a good solution. It was one of my choices, but as it requires additional circuits, I wanted to hear more suggestions.

     If I am not bothering you, let me tell a little more about our application. We have a modular eletronics poduct line called Nanoshields, and we try to make them as flexible as possible, so our users can read up tp 16 channels of ADC, 15 channels of themocouple or switch 11 lamps at the same time, just to name some examples.  Using an ADC with four channels would be a good alternative, but we need the flexibility for users who want to measure just one bridge and users who want several (I think 10 to 15 is a good mumber), so a 2 channel device like ADS1230 with the buffer sounds like a suitable choice. 

     ADS1234 and ADS1232 are outstanding chips, but unfortunately is a little costly for our target. There are cheaper (chinese) competitors, but we think that TI reputation is a good competitive advantage. Do you have other alternatives with better specs than ADS1230 for general porpouse bridge measurement with equivalent cost? 

     Thanks.

  • 0 in reply to Gustavo Furlan
    TI__Guru** 112795 points

    Hi Gustavo,

    Keep in mind that the ADS1230 is not 2 separate channels, but one differential channel.  It also has just two gain options (64 and 128) and a restricted common mode range.  It is not possible to make a single-ended measurement that is ground referenced.

    The ADS1220 is a better device for a variety of sensor types.  It is a little more expensive than the ADS1230, but the device offers a whole lot more as it has the capability of 4 single-ended measurements or 2 differential measurements.  The device also has a chip select, so adding additional devices will not be an issue.  It is well suited for both bridge and TC measurements.  It can also support measurement of RTDs exciting the RTD with internal current sources.  The level of integration for the cost is really quite impressive and the power is low.  It also available in both a TSSOP package and a QFN if you need a smaller device footprint.

    Best regards,

    Bob B