Quad-Channel, Analog Output Module - Review

Table of contents

RoadTest: Quad-Channel, Analog Output Module

Author: fpobdoc

Creation date: 9 Sep 2017

Evaluation Type: Evaluation Boards

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?:

What were the biggest problems encountered?: The software does not communicate with the DAC8775 evaluation module, preventing any further testing

Detailed Review:

This is a review of the DAC8775 on a TIDP215 E1 evaluation board.  The GUI software is also labelled as DAC8775EVM.

References

• DAC8775EVM Users Guide, SBAU248, November 2016.  Accessed at www.ti.com/lit/ug/sbau248/sbau248.pdf
• Reducing Size of Group-Isolated PLC Analog Output Modules, webinar June 20, 2017.  Accessed at training.ti.com/webinar-more-channels-less-space-new-trends-highly-integrated-dacs
• Less Than 1-W Quad-Channel, Analog Output Module with Adaptive Power Management Reference Design, March 2017.  Accessed at www.ti.com/lit/ug/tiducv5/tiducv5.pdf

Overall impression: Poor

    Hardware: Appears to be well designed though the connector is fragile, incorrect cable was provided

    Software: Communicates with the board but does not function correctly

Supplied hardware

    TIDP215 E1 board, featuring the DAC8775

    SM-USB-DIG

    USB cable, Type A to Type B connectors

Unboxing

I received the entire RoadTest kit in a single box from Element 14.

The first two things that I noticed were that the evaluation module had already been opened and that the wrong USB cord was shipped.  Rather than the supplied USB A to USB B cable, TI should have supplied a USB Type A extension cable.  The supplied cable was useless in this case and set aside.

The evaluation board looks to be nicely laid-out.  Unfortunately, it didn't match up at all with the photos or instructions in the DAC8775EVM users guide.  This guide is a combination of hardware and software guide but is unhelpful.  For instance, the guide offers the use of communication test points and jumpers that aren't available on this module.

The software is only available for the PC.  I installed it on a Toshiba laptop running Windows 10 with a 15" screen and a maximum resolution of 1366x768.  The software did not fit on the screen and there was no way for me to resize or adapt the window to see the lowest part of the interface.  I could plug my laptop into an external monitor, but this was inconvenient and shouldn't be necessary.

Upon plugging the module into the USB port, one green LED lit up followed by a second.

The connection between the interface and the board appears to be fragile and could be misaligned.  I don't know why TI could not have used a standard plug that would be more robust.

After plugging it in, I used the Simple I/O feature of the software.  I was able to write and read to Address A with appropriate changes in the register.  I interpret this as having a valid connection from computer to interface to module.  This was the last success that I had in this process.

I then went to use the standard interface.  This appears to offer a number of ways to test the DAC8775, including fixed and ramped voltages, fixed and ramped currents, and calibration adjustments.  Unfortunately, I was totally unable to detect any voltage on any of the four outputs.  I did measure 3.3v being supplied to the module (both suggesting that the rail was active and that my DVM is functioning normally).

The one thing that I have not done yet is try to insert a higher voltage onto the module.  I believe that J6 is for an external voltage supply but am unclear about its limits, polarity of the terminals, etc.  I'll work on this next.

In the end, this was quite disappointing.  I had hoped to use this module as the basis for a dual rail precision power supply.  I may put more effort into this in the future but, at this point, I'm too frustrated to continue.  My guess is that the board works but that the software is not communicating with the DAC.