AN3077 datasheet(40/82 Pages) STMICROELECTRONICS

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Functional safety requirements for application software

AN3077

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DocID16384 Rev 10

the ADC samples the internally generated voltage while in the sampling phase the ADC

samples analog input coming from pads (See Figure 10).

Reference voltage which can be used during presampling phase is either

VDD_HV_ADR0/1 or VSS_HV_ADR0/1.

If there is an open failure in the analog multiplexing circuitry, the signal converted by

the ADC is not the analog input coming from the pad, but the presampling reference

voltage (VDD_HV_ADR0/1 or VSS_HV_ADR0/1).

This BIST must be run for each analog input used by the safety function.

Since the pads dedicated to analog inputs are of type INPUT, a missing enable from

the SIUL results in an open failure.

Note:

Rationale: To detect open failures of the channel multiplexing circuitry (See Figure 9)

Figure 9. Software BISTs to test the multiplexing circuitry (ADC_SWTEST_TEST1)

Note:

Implementation hint: Presampling can be enabled on a per channel basis through the

ADC_x_PSR0 register.

ADC_x_PSCR[PREVAL0] selects which reference voltage is used to precharge/discharge

the ADC internal capacitor.

ADC_x_PSCR[PRECONV] register shall be 0 (See “Analog-to-Digital Converter (ADC)”

chapter in the Device_Number Reference Manual for details on the presampling feature).

ADC

Reference

value 1

pins

ADC

Reference

value 1

pins

ADC

Presampling phase

Open detection:

Conversion phase

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