AN4371 Datasheet, PDF (10/29 Pages) STMicroelectronics – In automotive more and more often comes in foreground

ADC built-in self-test algorithms
2
ADC built-in self-test algorithms
AN4371
ADC contains three self test algorithms in order to test its functionality.
The SPC56xx uses two types of parameter settings to define the ADC self-test operation:
• Sample phase duration settings programmed into the INPSAMP_S, INPSAMP_RC,
and INPSAMP_C fields of the Self-Test Configuration Register (STCR1).
• Threshold values for analog watchdog algorithms
In order to support different loading and switching times, several different conversion timing
registers (CTR) are present. There is one register per channel type.
Table 3. Sampling phase duration for the test conversions
INPSAMP_C
Sampling phase duration for the test conversions related to the algorithm C. Valid
self-test values for this field are given below.
Minimum: 0x18
Maximum: 0xFF
INPSAMP_RC
Sampling phase duration for the test conversions related to the algorithm RC.
Valid self-test values for this field are given below.
Minimum: 0x60
Maximum: 0xFF
INPSAMP_S
Sampling phase duration for the test conversions related to the algorithm S. Valid
self-test values for this field are given below.
Minimum: 0xFF
Maximum: 0xFF
Table 2 represents the typical values for INPSAMP_x register. For detailed description of
INPSAMP_x calculation please refer to the Reference Manual.
Table 4. Sample phase settings
Register field
Recommended setting
INPSAMP_C
0x18h
INPSAMP_RC
0x60h
INPSAMP_S
0xFFh
Recommended setting for INPSAMP_S is the maximum value of this register field due to
slow sample capacitor settling time at low temperature for S0 algorithm.
2.1
Self-test execution flow
The number of channels converted at the end of each chain is 1 (except for Algorithm S, in
which all the steps are performed at once without any functional conversion interleaved). In
Scan Mode, consecutive steps of selected self test algorithm are converted continuously at
the end of each chain of normal conversions.
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