Part Number: TIDA-010982
Hi,
AFE chip loop not able to regulate current when input voltage is low(8V, 10V) with 250E resistance in series. as it is required for communication with HART modem. and also it could not regulate the loop with 500E in series that is required for HART physical layer testing.
Without series resistor, loop current has no issue.
Field Transmitter Platform: 4mA to 20mA Loop-Powered Interface Reference Design (Rev. A)
circuit is exact same for loop as given in this application note.
/Anurag