Functional safety requirements for application software
Safety Manual for MPC5777M, Rev. 1.1
NXP Semiconductors 29
Figure 1. Block scheme of the SAR ADCs, including the supervisor ADC
The supervisor ADC can be a source of latent failures. To detect these latent failures, before it can be used
to verify the behavior of functional ADCs, a test shall be executed once after the boot.
Assumption: [SM_FMEDA_153]To detect latent failures, the supervisor ADC shall acquire some known
internal analog voltages and compare them with the expected values before the supervisor ADC can be
used for monitoring the functional ADCs. [end]
Values which must be acquired are:
• [SM_FMEDA_154]Bandgap ADC measurement. [end]
• Internal analog voltages listed in section “Internal reference” of the “Analog-to-Digital Converters
(ADC) Configuration” chapter of the MPC5777M Reference Manual.
A similar procedure shall be applied on the functional ADCs that will be used for acquiring safety relevant
data as described hereafter.
Input mux
analog switch
pad cells
ADC Bandgap
Temp Sensor
IRC Reference
PMC Signals
Sigma-Delta
ADC inputs
2nd
Level
SoC
Mux
SAR ADCB
SAR ADC3
SAR ADC2
SAR ADC1
SAR ADC0
Bias
Generator
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