DAC161S997: Loop Error

Caelyn Evans

Part Number: DAC161S997

Hello,

We are using DAC161S997 as a self-powered transmitter. We have followed the application schematic provided in the datasheet and in this forum. We are using 24V as loop power for 4-20mA output. The device goes into loop error on startup. Any help with this is appreciated. Thanks!

Relevant schematic parts (DAP is not visible but connected to ground/COMA/COMD):

Oscilloscope shots of SPI signals:

Send DAC output value, transfer to register, nop, status request, nop

Status: loop error occurring, no SPI or frame error

over 1 year ago

0 Paul_Frost over 1 year ago

TI__Guru 53163 points

Hi Caelyn,

Generally we see this with grounding issues. Note that this device creates it's own ground reference voltage (COMA and COMD). You should ensure that your supply is truly a floating supply, and that the VLOOP- can be negative with respect to COMA/COMD. if VLOOP- is ground in your lab, then connecting things like scopes and digital analyzers can break the current loop regulation.

Thanks,

Paul

0 Caelyn Evans over 1 year ago in reply to Paul_Frost

Prodigy 10 points

The only connection we have to VLOOP- is a resistor to ground to measure the current.

0 Paul_Frost over 1 year ago in reply to Caelyn Evans

TI__Guru 53163 points

Hi Caelyn, that actually sounds like that could be the issue. Can you sketch your instrumentation configuration?

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DAC161S997: Loop Error