ADS1147: ADS1147

Matej,


I don't know of any available arduino code for the ADS1147, but a if you just do a google search on "ADS1147 arduino" there are a few examples that pop up.

The one thing that I was concerned about is that you want to measure an AC voltage. Note that the ADS1147 is a delta-sigma type of ADC meaning that the input is sampled many times to make a single output data conversion. A digital filter is then used to get the output data and this filter will have an frequency response depending on the output data rate. Table 6 in the ADS1147 datasheet gives some of the digital filter specifications, while Figures 25 through 35 give a graphical representation of the frequency response.

Read through the digital filter section and see if the device still works for you. There are other specifications and limitations of input range that may be important to you. If you can more accurately describe your application, it might help to discuss the system you want to put together.


Joseph Wu

Matej,


The only generic schematic that I can point you to is the ADS1147 EVM (Evaluation Module) schematic. You can find it here:

www.ti.com/.../sbau148b.pdf

For the EVM, we have extra circuitry to test a variety of different configurations so you can simplify this schematic. I would connected AVSS and DGND (as long as you don't need bipolar supplies). You can probably also remove the buffer from the external reference (REF5020) and connect it to REF0P/REF0N directly. Another option would be to remove the external reference and use the internal voltage reference instead. If you tied the CLK pin to ground, you could also remove the clock circuitry as well.

After that, it would be a rather simple schematic to connect to a microcontroller. Again, I don't know what you are specifically measuring, so there may be alterations to the schematic you'll need to make.


Joseph Wu

Matej,


I'm not really sure what it is that you are measuring based on the description in 22.5, but I do have a two comments.

If you had intended to connect AINN to ground and allowed AINP to go from +5V to -5V, then you will still need more conditioning to get the voltage in to the input range of the ADC. This is what I think you meant by using a voltage divider to drop 750Vpp to +5V and -5V.

First, the input voltage for any analog input pin of the ADS1147 must be within AVSS+0.1V to AVDD-0.1V for the ADC to measure the input signal. This is the limit when the PGA=1. In higher gains, the input range of the ADC is more limited because of the input and output ranges of the PGA itself. This is described on page 18 of the datasheet. The ground is not in the input range of the device unless the supplies are bipolar (using 2.5V for AVDD, and -2.5V for AVSS).

Second, the maximum input you can measure for the ADS1147 is 4V because the reference voltage is limited. The largest differential reference input voltage is AVDD-AVSS-1V. With a unipolar supply of +5V, the reference maximum would be 4V.


Joseph Wu