AD7731: Continuous Read Mode and Conversion Mode

Document created by analog-archivist Employee on Feb 23, 2016
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In our application the AD7731 does not stop "continuous conversion mode".
Is it enough to write a 1/1  to RW1/RW2 into communication register?
(The RDY_ pin signals a valid results always after 1,6ms(600Hz) - like during
continuous conversion mode)

Does "stop continuous read mode" and "stop continuous conversion mode" mean the
same?
Does AD7731 maybe make one more conversion after stopping it?
Do I may have to reset the AD7731 to stop it?

 

The AD7731 "Continuous Read Mode" and "Continuous Conversion Mode" are two
different things.

The continuous READ mode
========================
is related to the digital interface. In this mode, the interface doesn't need
to write to the communication register again and again, for repeatedly reading
the same register. That could be for example the data register - to only read
data once the part was calibrated and configured to desired mode of operation,
or could be reading the status register, where due to limited number of wires
the RDY pin is not used.

To start and stop continuous read mode, write the appropriate value to the
RW1/RW0 bits in the AD7731 communication register. (Datasheet page 13.)


The continuous CONVERSION mode
==============================
is related to the ADC converter itself and means that the new conversion is
started automatically and immediately after the previous has been finished. The
RDY pin goes low when the new result is ready for reading. The RDY goes high
when the data are read. In case the data are not read during the whole next
conversion period, the RDY would go high for a short time just prior the end of
conversion to make sure that there is the high to low transition flagging the
end of each conversion.

To start and stop the continuous conversion mode, write the appropriate value
to the MD2/MD1/MD0 bits in the mode register. (Datasheet page 15.)

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