DAC121C085: Question about DAC121C085 Vout

user4872449

Part Number: DAC121C085
Other Parts Discussed in Thread: DAC8551, XTR116

Hi,

I am trying to use DAC121C085 with xtr116 for 4-20mA output. I saw a design for DAC8551 with xtr116 and DAC8551 has a RC circuit which connected to Vref of XTR116. Is that needed only for DAC8551 or a plus for data quality for every DACs ?

over 6 years ago

0 Garrett Satterfield over 6 years ago

TI__Expert 5820 points

Hello,

C1 and R2 form a filter to reduce any high frequency noise on the reference output. These components are not required for operation but may be a plus for any other device using the XTR reference voltage. It certainly won't have a negative impact since the reference voltage is constant.

Thanks,
Garrett

0 user4872449 over 6 years ago in reply to Garrett Satterfield

Intellectual 760 points

how abaut r1, r3, r4 , r5 ?

0 Garrett Satterfield over 6 years ago in reply to user4872449

TI__Expert 5820 points

Hello,

R1 and R3 set the zero-scale current based on the reference (4mA). R4 and R5 set the span (16mA) based on the DAC output voltage. This is shown in Section 2.1 of the reference design guide. R5 in Figure 2 corresponds to (R1+R3) in the schematic, and R2 in Figure 2 corresponds to (R4+R5) in the schematic.

Thanks,
Garrett

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DAC121C085: Question about DAC121C085 Vout