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.
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?
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.
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.
Thanks for the reply Bob and Knight!
I didn't know about the ohm meter thing...sounds pretty good.