Usage of dedicated IDAC pins

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    Question: What are the advantages of routing the IDAC’s output to the dedicated IDAC output pin instead of other GPIO pins?



     Each IDAC in PSoC 3/5 has a dedicated output pin. The IDAC output may be routed to this dedicated pin or any of the other GPIO pins in the device. There are two advantages of using the dedicated pin over other GPIO pins:

    •   The dedicated route has a very low series resistance compared to the route through the Analog global/Analog Mux that would be used if other GPIO’s are selected. The dedicated route has a resistance that is less than 200 ohms from IDAC to GPIO. On the other hand, a route through the analog globals can be 500 ohms or more. An increase in the series resistance means an increase in the voltage drop across the routing path, which in turn would limit the compliance voltage of the current source at the pin.
    •   Using these dedicated pins also frees up routing resources that can be used for other parts of the design. These dedicated pins can be used irrespective of the current range you use with the IDAC. Therefore, you can use the dedicated pins any time an IDAC is used to maximize routing resources.

    Refer to the application note “PSoC® 3 and 5 - Pin Selection for Analog Designs - AN58304” for more details on analog routing architecture in PSoC 3/5.