JAJSNU4A May 2023 – June 2024 AFE78201 , AFE88201
PRODUCTION DATA
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In addition to the diagnostic ADC and alarms of the AFEx8201 described in Section 6.3.2 and Section 6.3.3.6, the XTR305 has several additional diagnostic features.
IA Common-Mode Overvoltage Range (EFCM): This flag goes low as soon as the input of the IA reach the limits of the linear operation for the input voltage.
Overtemperature Flag (EFOT): This flag goes low if the chip temperature reaches 140°C and resets as soon as the temperature cools down to less than 125°C.
Load Error (EFLD): Indicates fault conditions driving voltage or current into the load. In voltage-output mode, the device monitors the voltage limits of the output swing and the current limit condition caused from short or low load resistance. In current-output mode, the alarm indicates a saturation into the supply rails from a high-load resistance or open load. The fault flag helps detect whether the analog output wire is broken or shorted. This feature improves the reliability of the analog output function. In case of a short-circuited load, the output current is limited to ±20 mA in voltage-output mode, and ±32 mA in the current-output mode.
All three fault flags are open collector, and therefore require pullup resistors.
Analog Output Monitor: In current-output mode, the IA output is connected to a resistor through the IAOUT pin and the IMON pin is internally disconnected. IAOUT is proportional to the output voltage given by Equation 18. This current is converted into voltage across a 500‑Ω resistor that can be sensed by the ADC on the AFEx8201. This current measurement enables a monitor of the output power delivered to the load. If the load resistance is known, then the output current can be calculated and compared with the commanded value.
During voltage-output mode, 1/10th of the output drive current is mirrored onto the IMON pin and IAOUT is internally disconnected. The IMON pin is connected to a 1-kΩ resistor. The voltage across this resistor is sensed by the ADC on the AFE88201. If the output load is known, then the output voltage can be calculated and compared with the commanded value. The output power delivered to the load can also be calculated. Output monitor functions help detect load changes enabling predictive maintenance, which increase reliability of the analog output function.