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HT66FM5440
Brushless DC Motor A/D Flash MCU
HT66FM5440
Brushless DC Motor A/D Flash MCU
Comparators
Four independent analog comparator
s
are
contained within the device. The
se
function
s
offer
flexibility via their register controlled features such as power-down, hysteresis etc. In sharing their
pins with normal I/O pins the comparator
s
do not waste precious I/O pins if the
re
function
s
are
otherwise unused.
C3P
C3X
C2P
C2X
C1X
C0X
C1P
OPA0 output
DAC output
C1N
C2N
C3N
Comparator 2
Comparator 3
Comparator 1
Comparator 0
Note: When the PB3S1~PB3S0 bits in the PBPS0 register are configured to 10B, the switches
circled in the block diagram will be turned on, in which case C1N, C2N and C3N is shorted
internally and connected to the CPN pin.
Comparators Block Diagram
Comparator Operation
The device contain
s
four comparator function
s
which
are
used to compare two analog voltages
and provide an output based on their difference. Any pull-high resistors connected to the shared
comparator input pins will be automatically disconnected when the comparator is enabled. As the
comparator inputs approach their switching level, some spurious output signals may be generated
on the comparator output due to the slow rising or falling nature of the input signals. This can be
minimised by selecting the hysteresis function will apply a small amount of positive feedback to
the comparator. Ideally the comparator should switch at the point where the positive and negative
inputs signals are at the same voltage level. However, unavoidable input offsets introduce some
uncertainties here. The hysteresis function, if enabled, also increases the switching offset value.