• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 127 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.

DAC161P997: DAC not outputing 4-20mA.

Hamza Alpiyal
Prodigy 150 points
Part Number: DAC161P997

Tool/software:

Hi, I designed a PCB using this particular DAC.But unfortunately the loop is not working.

The DAC is responding to MCU commands and also giving status, in status it is showing loop error, and the DAC is also not working from giving loop voltage. 

For this PCB I followed reference design from DOC tidu182a(RTD Temperature Transmitter for 2-Wire, 4 to 20-mA Current Loop Systems).

Here is the schematic of my PCB.

  • 0
    TI__Guru* 93735 points

    Hamza,

    I don't really see anything that would be a problem. It generally looks like it's connected correctly. I would check to see that the Schottky diodes are placed in the correct orientation to allow current flow.

    After that, make some measurements around the device and board. What's the loop voltage and the loop current? What is the voltage at the OUT pin, and what is the voltage at the BASE pin? Make sure that the LDO is providing 3.3V to the device. You can also measure the voltages across R3 and R6 to see how much current is running through those resistors.

    Make those measurements, repost back here, and we can review it.

    Joseph Wu

  • +1 in reply to Joseph Wu
    Prodigy 150 points

    It started to work. I was giving 5v on input, but when I gave 12v it started to work.

  • 0 in reply to Hamza Alpiyal
    TI__Guru* 93735 points

    Hamza,

    I'm glad you were able to get it to work. I would note that for this TI Design (https://www.ti.com/lit/ug/tidu271/tidu271.pdf), The power supply range is listed as 18V to 36V om Table 1, page 2 of the design guide. Additionally, the typical power supply is listed as 24V (from page 42 of the design guide). This voltage is common for loop applications.

    Joseph Wu