RM0091 Comparator (COMP)
Doc ID 018940 Rev 1 217/742
The output can also be internally redirected to a variety of timer input for the following
purposes:
● Emergency shut-down of PWM signals, using BKIN
● Cycle-by-cycle current control, using OCref_clr inputs
● Input capture for timing measures
It is possible to have the comparator output simultaneously redirected internally and
externally.
14.3.4 Interrupt and wakeup
The comparator outputs are internally connected to the Extended interrupts and events
controller. Each comparator has its own EXTI line and can generate either interrupts or
events. The same mechanism is used to exit from low power modes.
Refer to Interrupt and events section for more details.
14.3.5 Power mode
The comparator power consumption versus propagation delay can be adjusted to have the
optimum trade-off for a given application.
The bits COMPxMODE[1:0] in COMP_CSR register can be programmed as follows:
● 00: High speed / full power
● 01: Medium speed / medium power
● 10: Low speed / low power
● 11: Very-low speed / ultra-low power
14.3.6 Comparator LOCK mechanism
The comparators can be used for safety purposes, such as over-current or thermal
protection. For applications having specific functional safety requirements, it is necessary to
insure that the comparator programming cannot be altered in case of spurious register
access or program counter corruption.
For this purpose, the comparator control and status registers can be write-protected (read-
only).
Once the programming is completed, using bits 30:16 and 15:0 of COMP_CSR, the
COMPxLOCK bit must be set to 1. This causes the whole COMP_CSR register to become
read-only, including the COMPxLOCK bit.
The write protection can only be reset by a MCU reset.
14.3.7 Hysteresis
The comparator includes a programmable hysteresis to avoid spurious output transitions in
case of noisy signals. The hysteresis can be disabled if it is not needed (for instance when
exiting from low power mode) to be able to force the hysteresis value using external
components.
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