Texas Instruments MSP430x4xx - Manual (Page 490)

Scan IF Operation
24-30 Scan IF
24.2.6.2 LC-Sensor Envelope Test
The envelop test measures the decay time of the oscillations after sensor
excitation. The oscillation envelope is created by the diodes and RC filters. The
DAC is used to set the reference level for the comparator, and the comparator
detects if the oscillation envelop is above or below the reference level. The
comparator and AFE outputs are connected to Timer1_A5 and the
capture/compare registers for Timer1_A5 are used to time the decay of the
oscillation envelope. The PSM is not used for the envelope test.
When the sensors are connected to the individual SIFCIx inputs as shown in
Figure 24−16, the comparator reference level can be adjusted for each sensor
individually. When all sensors are connected to the SIFCI input as shown in
Figure 24−17, only one comparator reference level is set for all sensors.
Figure 24−16. LC Sensor Connections For The Envelope Test
Power
Supply
Terminals
SIFCI0
SIFCI
SIFCI1
SIFCI2
SIFCI3
470 nF
AV
CC
DV
CC
DV
SS
AV
SS
SIFVSS
470 nF
SIFCOM
SIFCH1
SIFCH0
SIFCH2
SIFCH3