XTR105: XTR105 output 55mA current issue

Hi Mickey,

I think you forgot to post the attachment. It sounds like the customer has not properly isolated the input signal ground, IRET, from the loop supply ground. I would be happy to look over the schematic for you.

Hi Zak,

Sorry, I really forgot to upload the schematic. Now I have updated. Would you check the schematic?

Mickey,

Could you please elaborate on the customer's test conditions? Was this measurement taken with nothing connected to the inputs? The XTR is configured to excite an RTD, but if there is nothing connected to the inputs of the XTR then the only path for the reference currents to flow is through the inputs, which will definitely cause abnormal behavior. Also, could you please clarify what SGND is? Is this meant to be chassy ground and C7, C8, C9 are for EMI filtering? The IRET pin should serve as the reference for any input circuitry so if the customer is trying to add filtering to each of the inputs (C5 and C6) then these should be terminated at IRET.

Hi Zak,

I will confirm with the customer.

For the suggestions of the IRET pin, you mean that C5 and C6 are needed to connected to the IRET pin directly?

Thanks Mickey. Yes, these capacitors should be connected between IRET and the input pins.