TMS320F28377D: IEC60730 Table H.1 for ADC MUX (But the ADC is occupied)

Hi Hideaki,

ADC Mux is only one component of the overall ADC module. Other ADC module sub-parts includes S/H, ADC converter, Configuration/Results registers, Ref voltage, Arbitration and control, IO pads etc. which can also contribute to failure rate of ADC conversion. In order to safe/cover the entire conversion of input signal to results register, we recommend the ‘Hardware Redundancy’ as safety mechanism, where a signal input is redundantly converted by 2 individual ADC’s and then followed by comparison of results, either by internal or external input connection. This will detect both types of faults, Permanent (e.g. stuck-at) as well as Transient (e.g. SER bit-flips in control registers) errors. It may not be feasible to take the module offline during application run time for periodic pattern testing and ‘Hardware Redundancy’ will serve for continuous online diagnostic to detect faults (necessary and sufficient).

In order to test the test the functionality of the entire chain using a test pattern, lets say only at startup for detecting latent(permanent) faults, will require to have control of the inputs. Currently only select inputs of all four ADC are controllable from within MCU using DACOUT, to test all the mux combinations will require taking control of the input IO pad from external to MCU.

Other than Hardware Redundancy, we have below suggested safety mechanisms for detecting faults in ADC module and are described in Safety Manual.

 ADC3 - ADC Information Redundancy Techniques

-          The correlation between input signals can be used to check the integrity (for example, if the three phase voltage, V1, V2, V3 is being measured using ADC, the function V1 + V2 + V3 = 0 can be used to provide diagnostic coverage for input signal integrity and ADC conversion).

ADC8 - ADC Input Signal Integrity Check

-          Plausibility of input signal check using built in HW mechanism

ADC4 - Opens/Shorts Detection Circuit for ADC

-          Detect faults in the ADC input channel.

ADC6 - Periodic Software Read Back of Static Configuration Registers

-          Faults in CHSEL,ACQPS registers etc can be detected

ADC7 - ADC Signal Quality Check by Varying Acquisition Window

-          Varying amount of time the sampling capacitors allowed to charge

Regards,

- Ashish