Texas Instruments MSP430x1xx - Manual (Page 288)

Comparator_A in Applications
14-22
14.4.7 Compensating for the Offset Voltage of Comparator_A
Another way to improve the accuracy is to compensate for the effect of input
offset voltage without actually measuring it.
When CAEX = 0, the V
offset
is in series with V
ref:
V
CA0
= V
ref
+ V
offset
When CAEX = 1, the V
offset
is in series with V
CA0:
V
ref
= V
CA0
+ V
offset
⇒ V
CA0
= V
ref
– V
offset
Adding the result of two conversions (one with each input configuration) and
dividing by two will cancel the effect of the offset voltage.
V
CA0
+ V
ref
) V
offset
)
V
CA0
+
V
ref
*
V
offset
2 V
CA0
+
2 V
ref
å
N1 ) N2
2
+ Conversion without offset
N = Timer count
14.4.8 Adding Hysteresis to Comparator_A
When the voltage level applied to the + terminal is close to the voltage level
at the – terminal, the output of the comparator may oscillate. This can cause
the following two situations:
- The current consumption increases, since the signal path driven by the
comparator output is constantly charged and discharged.
- The software receives constant requests for service either via interrupt
service requests, or after successful polling of CAOUT or CAIFG.