Texas Instruments MSP430x1xx - Manual (Page 279)

Comparator_A in Applications
14-13
Comparator_A
14.4.3 Measuring Two Independent Resistive Element Systems
It is possible to measure two independent systems with one comparator. The
input multiplexer, which is controlled via CAEX, allows the two independent
systems to be isolated. See Figure 14–9. An example could be if one tempera-
ture sensor has a resistor range of 10 k
Ω
to 200 k
Ω
. The other sensor is in the
range of 1 k
Ω
to 1.5 k
Ω
. Two independent measurement paths are used to opti-
mize individual measurement performance. The conversion principle is identi-
cal to the one described in the previous section.
Figure 14–9. Two Independent Temperature Measurement Systems
_
+
0
1
CAF
Set
CAIFG
τ ∼
2
µ
s
0
1
0
1
0
1
0
1
CA0
CA1
0
1
V
CC
V
CC
R1
(ref)
R1
(meas)
P2CA0
P2CA1
VCAREF
CARSEL
0
2
1
3
3 2 1 0
CAREF
0.5
×
V
CC
0.25
×
V
CC
V
CC
V
CC
R2
(ref)
R2
(meas)
C1
C2
1
0
CAEX
CAON
VCC 0 V
1 0
CAON
VCC 0 V
1 0
e.g.
Capture
Input of
Timer_A
CAOUT to
External Pin