Part Number:XTR111
Hi Sir,
Attached SCH shows our 4-20mA conversion circuit which is part of the circuit in our design. Basically we used design of TI evaluation board for XTR111.
The 4-20mA accuracy of this circuit meets our requirement when ambient temperature is between -40C to +60C.
However, when temperature rises over +65C, the 4-20mA output current was out of our specification (< 2.5%) if Vin was below 2V.
The accuracy comparison can be found in the other attached file.
We measured the voltage of R226 (shown in attached SCH), this voltage only changed a little (less than 0.5%) compared with the voltage value at +22C.
It looks like that the current passing through B pole and E pole of Q8 significantly increased at +85C so that the 4-20mA output current accuracy was severely degraded.
Because we used TI's evaluation design, does any one of TI engineers know this issue? Is there any recommendation to get it improved?(Please visit the site to view this file)(Please visit the site to view this file)(Please visit the site to view this file)
Thanks
William Chen