Datasheet

to settle. If the supply voltage is guaranteed to be above 2.5V, the voltage doubler can be disabled by
writing the Low-Power Mux bit in the Control A register (CTRLA.LPMUX) to one. Disabling the voltage
doubler saves power and reduces the start-up time.
34.6.6 V
DDANA
Scaler
The V
DDANA
scaler generates a reference voltage that is a fraction of the device’s supply voltage, with 64
levels. One independent voltage channel is dedicated for each comparator. The scaler of a comparator is
enabled when the Negative Input Mux bit field in the respective Comparator Control register
(COMPCTRLx.MUXNEG) is set to 0x5 and the comparator is enabled. The voltage of each channel is
selected by the Value bit field in the Scaler x registers (SCALERx.VALUE).
Figure 34-6. V
DDANA
Scaler
COMPCTRLx.MUXNEG
== 5
SCALERx.
VALUE
to
COMPx
6
34.6.7 Input Hysteresis
Application software can selectively enable/disable hysteresis for the comparison. Applying hysteresis will
help prevent constant toggling of the output, which can be caused by noise when the input signals are
close to each other.
Hysteresis is enabled for each comparator individually by the Hysteresis Enable bit in the Comparator x
Control register (COMPCTRLx.HYSTEN). Hysteresis is available only in continuous mode
(COMPCTRLx.SINGLE=0).
34.6.8 Propagation Delay vs. Power Consumption
It is possible to trade off comparison speed for power efficiency to get the shortest possible propagation
delay or the lowest power consumption. The speed setting is configured for each comparator individually
by the Speed bit group in the Comparator x Control register (COMPCTRLx.SPEED). The Speed bits
select the amount of bias current provided to the comparator, and as such will also affect the start-up
time.
34.6.9 Filtering
The output of the comparators can be filtered digitally to reduce noise. The filtering is determined by the
Filter Length bits in the Comparator Control x register (COMPCTRLx.FLEN), and is independent for each
SAM D21 Family
AC – Analog Comparators
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Datasheet Complete
DS40001882D-page 938