Kontron CP372 - Manual (Page 36)

Functional Description CP372
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P R E L I M I N A R Y
2.3.1.2 Vext Functionality by Analog Current Outputs
In order to generate analog current output signals, the CP372 requires that the application pro-
vide an appropriate external source voltage (Vext) for each individual analog current output
channel.
The source voltage to be provided is by definition a function of the total output channel source
resistance and the maximum required output current. To take advantage of full scale, 0 to 20
mA, output, each channel must be supplied with a corresponding given minimum source volt-
age which in many cases will vary from channel to channel due to varying channel source re-
sistance.
As the CP372 allows for any combination of signal outputs: voltage or current, and current with
different source resistances, care must be taken to ensure that Vext requirements are met as
well as proper connection of output signals to their respective channels.
Where current outputs share a common Vext, so called common tie point pins are available at
CON2 for application usage. For each cluster there are two pins available, and the two pins of
each cluster are permanently tied together on the CP372 side of the CON2 connector. For this
reason only one common tie point is available for each cluster.
Refer to chapter 1 for the specification of Vext and chapters 4 and 5 for further information con-
cerning the configuration of analog outputs and system considerations for the integration of the
CP372 in applications.