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OpAmp pins | Cypress Semiconductor

OpAmp pins

Summary: 4 Replies, Latest post by danaaknight on 08 Feb 2013 03:54 PM PST
Verified Answers: 0
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Rocketmagnet's picture
131 posts




There are several uncomitted OpAmps on some PSoC3s

The outputs seem to be connected to specific pins. Does this mean I can't route them to other pins? Does it mean I can't route them to other internal devices? E.G. ADC.

The inputs also seem to be connected to specific pins, but according to the TRM, there seems to be more options for connecting them to other buses. Is there some advantage to using those specific pins rather than other pins?

Is there any advantage to using those OpAmps rather than the ones in the SC/CT blocks?




user_14586677's picture
7646 posts

These ap notes may help -


Related Application Notes

  AN54181 – Getting Started with PSoC 3
  AN60631 – PSoC 3 Clocking Resources
  AN58304 – PSoC 3 and PSoC 5LP - Pin Selection for
Analog Designs
  AN58827 – Internal Routing Considerations for
PSoC 3 and PSoC 5LP Analog Designs
  AN54460 – Interrupt Handling in PSoC 3
  AN60580 – SIO Tips and Tricks in PSoC 3 and
  AN66083 – Using Sleep and Hibernate Modes in
PSoC 3
  AN52705 – PSoC 3 and PSoC 5LP - Getting Started
with DMA


Regards, Dana.

user_1377889's picture
9301 posts

Whenever you use one of the opamps its dedicated pins will be in use and cannot be used by another component. The router is able to connect that opamp to another pin when required, but the dedicated pins will still be in use. So the route is "hopping" from the dedicated pin to the target.

This was used to have low-impandence connections for some of the internal devices to the outside.



user_14586677's picture
7646 posts

Modificatiuon to what Bob said. Just the OpAmp output pin becomes dedicated,

not its inputs.


Opamp Pin Selection


The opamps are connected to the GPIOs in such a way that they can be used without

any internal analog global busses, See Figure 12. If all connections to the opamp are

external through the GPIOs, it is a good idea to use the dedicated pins. In many cases,

the opamp may be used as a buffer to an internally generated signal, such as a buffer to

a VDAC output. In this case the dedicated opamp input pins may be ignored and used for

another purpose. After the opamp is enabled, the dedicated output GPIO will always be

driven by the output of the opamp. This GPIO is now dedicated to the opamp output and

cannot be used for another signal. Even if this signal is only used internally, the dedicated

output pin will be driven by the opamp. This guarantees that the resistance between the

opamp and GPIO pin is low, about 5 ohms. If you must use a different pin for the output,

the dedicated output pin still outputs the signal. If the opamp is not used, it has no affect

on the GPIOs directly connected to it. These GPIO pins operate as any of the other GPIOs

when the opamp is disabled.  

Regards, Dana.



user_14586677's picture
7646 posts

Makes one wonder if the output pin can be over-ridden with a register write.


After all out R in the path of an OpAmp output, its effective Zo becomes divided

by loop gain.


Regards, Dana.

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