DAC161P997: DAC161P997 Breaks down without reason

user4872449

Part Number: DAC161P997
Other Parts Discussed in Thread: DAC161S997

I have a converter which converts 24V(loop+) to 5v and a LDO which converts 5V to 3.3V. Something happens without a reason like letting output pin of DAC(loop-) float or connecting it to ground throug 100ohm or sometimes when i connect device to power source it starts drawing much more current then useal. but this is not for sure i did all of these things 100 times and nothing happened 99 times.anyway if everyhing stops working. when i check the voltage difference between loop- and those converter's outputs, i see a voltage around 20V.But it is more likely loop- is -20V(negative) And if i change DAC with new one everything is OK. and oddly nothing gets damage because of this.

over 6 years ago

0 Garrett Satterfield over 6 years ago

TI__Expert 5820 points

Hello,

It is difficult for me to follow exactly what leads to this problem. When this occurs is the 3.3V supply and 24V to 5V DC/DC still the correct voltage?

I would not be surprised to see a 20V difference between loop supply and OUT pin if you have a load connected in series with the supply.

Are you able to provide your full schematic for review. One thing I notice is you have COMA and COMD referenced to different grounds. What 'GND' and 'AGND'?

Thanks,
Garrett

0 user4872449 over 6 years ago in reply to Garrett Satterfield

Intellectual 760 points

I am measuring between loop- and outputs of those converters and they are like around 20v. maybe this is normal but i broke all of my DACs so i order new one. until i get them i cant say anything. but i know this device is not working. I use star ground for the noice.

0 Garrett Satterfield over 6 years ago in reply to user4872449

TI__Expert 5820 points

Hello,

I do not see anything with the schematic that would cause damage to DAC161S997. It is pretty hard to say what could be happening given the information you provided. Are you planning on testing with a new device? If so perhaps you can provide more details.

Thanks,
Garrett

0 user4872449 over 6 years ago in reply to Garrett Satterfield

Intellectual 760 points

Is amy multimeter cause this ? Like difference Rloads. I an consuming dac161s like candy

0 Garrett Satterfield over 6 years ago in reply to user4872449

TI__Expert 5820 points

Hello,

A multimeter will not cause a problem because it is just a very small series resistance in the loop. The device can maintain current regulation when the load changes.

Have you been able to replicate the problem consistently? If so can you provide details on what you do before you see damage to the device?

Thanks,
Garrett

0 user4872449 over 6 years ago in reply to Garrett Satterfield

Intellectual 760 points

I have a DPDT switch for changing 4-20mA output to 0-10V if i change it while the device still on, dac161 gets damage ?

0 Garrett Satterfield over 6 years ago in reply to user4872449

TI__Expert 5820 points

Hello,

This may be causing a some type of transient that is damaging the device. The device is not damaged if the output is not switched while the device is on, correct?

I would monitor the voltage on VA, VD, BASE, and OUT while this switching occurs to see if you can identify the issue.

Thanks,
Garrett

0 user4872449 over 6 years ago in reply to Garrett Satterfield

Intellectual 760 points

i found a solution for switch but i need to ask something else. The only pins i have are loop- and loop+. I dont have any other pin entrence. That means i dont have any other ground entrence.DAC161S997 provides ground right ? I have no isolator.

0 Garrett Satterfield over 6 years ago in reply to user4872449

TI__Expert 5820 points

Hello,

Can you share your solution to the damage you were seeing? It may be helpful if someone else tries a similar switch configuration.

That is correct only loop- and loop+ should connect to the supply and load resistor. Loop+ should connect to the high side of the power supply, and loop- should connect to the low side through the load resistance. The DAC161S997 local ground will be a different voltage than the supply ground. Isolation is not required for operation.

Thanks,
Garrett

0 user4872449 over 6 years ago in reply to Garrett Satterfield

Intellectual 760 points

I just used an other DAC for 0-10V output. Thank you so much for your help.

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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DAC161P997: DAC161P997 Breaks down without reason