A set window comparator provides temperature monitoring for all GPIO inputs with the external thermistor network pulled up to TSREF. This comparator function is entirely separate from the ADC function and, as such, even if the ADC function fails, the analog comparators still flag the crossing of the overtemperature (OT) and undertemperature (UT) comparator thresholds. The programmed thresholds are translated through DACs to the comparators.

Figure 9-21 OT and UT Protectors

The OT and UT thresholds set by OTUT_THRESH[OT_THR4:0] and OTUT_THRESH[UT_THR2:0] bits are the same for all active GPIO inputs. The active GPIO inputs are defined by the GPIO_CONFn[GPIO*2:0] (where n = 1 to 4, * = 1 to 8 for the corresponding GPIO input). The GPIO has to be configured as ADC and OTUT inputs to be considered as active GPIO inputs for the OTUT protectors.

The OTUT comparators use TSREF as reference, and so the detection is in ratiometric form. The OT protector detects an OT fault on a particular GPIO if the (GPIO voltage/TSREF) is less than the OTUT_THRESH[OT_THR4:0] setting. The UT protector detects a UT fault on a particular GPIO if the (GPIO voltage/TSREF) is more than the OTUT_THRESH[UT_THR2:0] setting. The OTUT protectors assume the NTC thermistor is used for temperature monitoring.

MCU ensures TSREF is enabled before starting the OTUT protectors. Failing to do so, the OTUT protectors will flag all OT and UT faults on all GPIO inputs as an indication of abnormal detection.