Connecting the op-amp to the SARMUX

[Mrinal]

 Hello!

   

Is it ok to route the output of the op-amp (in follower configuration) to the SARMUX internally?

   

Since the routing is internal, a resistive load cannot be connected to the opamp output. Without resistive loading, is there a possibility of unstability and also inaccuracy dueto overshoots and oscilations?

   

Thanks...

[Bob_Marlowe]

The absence of a resistive load might not be the problem when the OpAmp is configured as follower.

   

But I have in mind that the routing to the Mux internally will be denied, since the Mux is dedicated to the input pins.

   

Give it a try, when routing works I am wrong.

       

Bob

[Mrinal]

 Thanks for the reply!

   

I tried connecting the opamp internally, and it doesnot flash an error.

   

The opamp output is probably routed through the analogue bus to the SARMUX. I suppose the SARMUX is connected to the analogue bus, isn't it?

[Bob_Marlowe]

When you select in the .cydwr file view the tab "Analog" you can see the routing for the analog signals and estimating the signal-resitance with the (right-click) ohm meter.

       

Bob

[ETRO_SSN583]

This routing is fine -

       

       

R loads not of concern generally speaking unless one is concerned with

   

Pdiss. Its C loads that present stability problems due to OpAmp Rout

   

forming a pole with Cload and creating excess phase margin. You can

   

always look at your stability in time domain by inputing a pulse to signal

   

path and looking at response, specifically damped sinusoid at output.

   

Many ap notes on web on this topic.

       

Although not speced I measured Rout recently of a OpAmp follower and

   

its ~ 8 ohms.

       

www.analog.com/library/analogdialogue/archives/43-09/edch%201%20op%20amps.pdf

       

Regards, Dana.

[Mrinal]

 Thanks for the reply Bob and Knight!

   

I didn't know about the ohm meter thing...sounds pretty good.

[ETRO_SSN583]

The ohmmeter allows you to get the path/route R from pin to component

   

you place.

       

video.cypress.com/video-library/video/Corporate/PSoC-Creator-Tutorial-Using-the-Ohm-Meter/1766619869...

       

Regards, Dana.