XTR116: XTR116

Hi Varun,

have you kept in mind that only 3.7mA is available at the Vreg pin of XTR116 to power external circuitry?

Also, what do you connect to the microcontroller? Eventually, optical isolation is necessary at the inputs of microcontroller as shown in figure 3 of dahasheet.

Ka

Yeah we are running our controller in 3MHz it will not take not more than 2.5mA, right now we have not connected any inputs our intension is to connect measure resistance and convert to 4-20mA

we are controlling 4-20mA through DAC which is accurate in producing the voltage.. when we connect XTR116 3% non linearity is there

Hi Varun,

what are the conditions (input signal voltage, output current, shunt resistance, etc.) when you detect the 3% error? And how do you calculate this error?

Have you measured the current running out of the Vreg pin?

Are you sure the DAC is running properly?

Kai

Hi Varun,

Below is TI's application note with DAC8551 that is interfaced with XTR116 in 2-wire V-to-I 4-20mA current loop. Note that marked orange nodes are referenced to Io or pin4 in XTR116 IC. These ground references are "floating" with respect to Pin4 or Io node. The XTR116 and DAC8551's ground is located on the right side, as shown in marked blue rectangular. 

Enclosed is the application note to describe how V-to-I works with DAC8551 part. 

https://www.ti.com/lit/ug/tiduao7/tiduao7.pdf?ts=1647891991803&ref_url=https%253A%252F%252Fwww.google.com%252F

From the schematic, it is not clear how grounds are referenced to pin4 or Io. The regulated 5Vdc from XTR106 has limited current sourcing capability, which is < 3.7mA as Kai pointed out. How Vloop power (loop supply ground) from P1 and P2 are referenced to the GND signals from MCP4725AIT and XTR116.  There are only one GND reference that both ICs should be referenced to, and the remaining Grounds have to  be "floating" in the current loop, which the application note below is addressed the design consideration.  

https://www.ti.com/lit/an/sboa107b/sboa107b.pdf?ts=1647894798451&ref_url=https%253A%252F%252Fwww.google.com%252F

We have designed a 4-20mA product in the datasheet they have told non linearity error is 0.003% but we are getting 3% error...

As Kai's last message, can you show us data points how nonlinearity is calculated? If the DAC is configured incorrectly, then the XTR116 will not produce the correct linear relationships. 

Please let us know if you have additional questions. 

Best,

Raymond