ADuC847 Burnout current pinout error

Document created by analog-archivist Employee on Feb 23, 2016
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I tested ADuC847 Burnout current to detect the short/open circuit. But it
deosn't work. And the ADuC847 Document said:
  "Burnout Current Enable Bit.When set, this bit enables the sensor burnout
current sources on primary ADC channels AIN4/AIN5 or AIN6/AIN7. Not available
on any other ADC input pins or on the auxiliary ADC (ADuC845 only)."
  I dont understand that "AIN4/AIN5 or AIN6/AIN7",these are not pairs of
differential input channels, the channels should be "AIN1/AIN2, AIN3/AIN4,
AIN5/AIn6, AIN7/AIN8", can you explain how does it work?

 

You are correct, there is a typo on the datasheet that is being corrected. I
am currently waiting for website to be updated with latest datasheet.
In the meantime the correct pin outs for the burnout currents is as
follows....Ain5/6 and Ain7/8.
The current generated is 200uA from each burnout source, therefore the test
this you simply need to monitor the current either directly or by the voltage
drop across a resistor. The way the burnout detect circuit works is described
on page 32 of the datasheet. Simply put it says that if the sensor goes open
circuit then the ADC will read full-scale (i.e. V=IxR where R = infinite)  and
where the sensor has shorted the voltage read will be 0 (again V=IxR where R =
0).

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