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4 IDacs but only 2 dedicated pins ? | Cypress Semiconductor

4 IDacs but only 2 dedicated pins ?

Summary: 2 Replies, Latest post by danaaknight on 10 Feb 2015 07:24 AM PST
Verified Answers: 1
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user_347933176's picture
35 posts

What am I missing ? I need a PSOC 3 or 5LP with 4x IDac 2mA range.

The knowledgebase article "Use of dedicated IDAC pins (12/24/2011)" says "Each IDac in PSOC 3/5 has a dedicated output pin". Using the Device Selector I see how many IDACs each component has so I choose CY8C3866LTI-067 (QFN-48 package). 

But this processor only has 2 IDAC:HI outputs (P0[6] and P0[7]). It has no P3 port so I assume I can only use 2 high-current IDAC outputs. 

Is this correct ? How can I get an overview of controllers having 4 high-current outputs ? By looking at the number of pins ?



user_78878863's picture
2553 posts

When you look at the CY8C38 family data sheet, you can find the pinouts for the different packages. From there you can see that only the 68 and 100 pin packages have 4 dedicated IDAC output pins.

user_14586677's picture
7646 posts

The datasheet says the dedicated pins "should" be used on high current

range. I would posit this is because of a compliance range issue keeping

the IDAC in constant I mode. What you could do is using the analog view,

ohmeter, look at a route to a low R path and try it again to a "normal" GPIO

and get an idea of difference in path.


Note Rdson onchip of a mux, path, has wide variation, and no specs to guide

you on this. My point would be that if your "load" is anything but a virtual ground

a less desired route would have significant impact on compliance in addition

to inherent IDAC architecture contribution.


You could do some trial testing/testbed on compliance issue to see how much

margin there is before IDAC is pulled out of compliance


Just a thought.


Regards, Dana.


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