SIMPLIS digital devices do not require a reference to the global ground node, which is node 0 in the main circuit and all subcircuits; as a result, SIMPLIS logic can appear anywhere in a power system - referenced to ground or to a power rail, such as -48V or left floating. With the exception of the digital constant, all digital devices allow you to use a ground-reference pin. Two simple rules define when a ground-reference pin is required:
The following circuit examples are intended to help you better understand these rules.
In the following schematic example:
This example circuit can be downloaded here: simplis_009_when_is_ground_ref_required_example_1.sxsch
The SIMPLIS classic digital logic family is the original logic family in SIMPLIS. These devices can be identified by the lack of additional lines on the lower left corner of the symbol. All devices in this family are treated as analog components and, if a digital device interfaces with a SIMPLIS classic digital device, the SIMPLIS digital device requires a ground-reference pin.
This example circuit can be downloaded here: simplis_009_when_is_ground_ref_required_example_2.sxsch
When a SIMPLIS digital device is connected to an analog component, the interfacing input or output voltage range is controlled by the edit dialog box entries on the Interface tab. The Input parameters and Output parameters boxes for the D-Type Flip-Flop are shown below.
If a required ground reference for a SIMPLIS digital device is missing, an error message is generated and the simulation stops. If the ground reference for U4 is removed from the first example, the error message would be as follows:
*** ERRORS REPORTED BY SIMPLIS *** **************************************** <<<<<<<< Error Message ID: 5045 >>>>>>>> The device X$U4.A_BUF has at least one analog output node but it does not have a gnd ref pin. *** END SIMPLIS ERROR REPORT ***
If you see this error message in your circuit, follow these steps to correct the errors: