SFFS779 December 2024 TMS320F28P550SJ
Integrity of PGA can be checked driving PGAx_IN input with a known set of values and monitoring output after conversion using on-chip ADC. DAC can be configured using software to provide a set of predetermined voltage levels. With an external connection, output of DAC can be connected to the PGAx_INP pin. This pin can be routed to both the PGA and ADC in parallel. ADC can convert both PGAx_OUT and the signal on the pin, and with SW scaling, can compare the ADC output to test if PGA amplified the input signal to an appropriate scale. PGAx_INM can be connected internally, or driven, as the system requires.
While using different ADCs to convert the native signal from the pin and the PGA output is possible, using the same ADC to eliminate any other error sources from the diagnostic is preferred.
Figure 6-9 shows the conceptual setup for testing the PGA using DAC and ADC.