Hello,
I want to develop a loopback test for an in-circuit part that was designed with autoshutdown enabled.
That is; ForceOn -> GND; /ForceOff -> VCC; /EN -> GND. VCC in my case is 3.3V
Is there a way I can bring the device out of shutdown mode to perform the loopback test?
I tried pulling the loopback to one side and the other. Pulling it to ground didn't work; Pulling it high introduced significant noise into the loopback, though it did bring the part out of shutdown mode.
Hi J,
Here is a table for how the auto power down feature works:
What you'll notice is that there are set ways that you can disable this feature. Specifically you would have to pull FORCEON high and you would leave FORCEOFF as high. This would disable this feature and you would just be in normal operation.
In your specific set up where FORCEON is grounded, in order to remain in normal operation, you would have to make sure that you are getting a valid RIN RS-232 level. This is a graph that shows a valid RIN level:
When RIN is in the region between -0.3V and 0.3V for more than 30 us INVALID will go low and auto power down with disable the drivers. You can check to see if the auto power down feature is active by probing the INVALID pin.
Let me know if you have anymore questions and if the issue is still persisting. We may need scope shots if that is the case.
Best,
Chris
