16 R/F COnVeRTeR
S1C63003/004/008/016 TeChniCal Manual
Seiko epson Corporation
16-3
(Rev. 1.1)
(1) R/F conversion using a DC bias resistive sensor such as a thermistor
Channel 0 supports this conversion method only, and channel 1 is selected into this method by setting ERF[1:0]
to "3." This method should be selected for R/F conversion using a normal resistive sensor (DC bias), such as
temperature measurement using a thermistor. At initial reset, channel 1 is set into this conversion method.
Figure 16.3.1 shows the connection diagram of external elements.
R
SEN
R
REF
V
SS
C
RFC
R
SEN
R
REF
Open
C
RFC
SEN0
(P51)
REF0
(P52)
RFIN0
(P53)
Channel 0
V
SS
SEN1
HUD
REF1
RFIN1
Channel 1
R
SEN
:
R
REF
:
C
RFC
:
Resistive sensor (e.g. thermistor)
Reference resistor
Oscillating capacitor
3.1 Connection diagram in case of R/F conversion
Figure 16.
CR oscillation waveforms are shaped by the schmitt trigger and sent to the measurement counter. The clock sent
to the measurement counter is also output from the RFOUT terminal while the sensor is oscillating. As a result,
the oscillation frequency can be measured by an oscilloscope or other equipment. Since this monitor has no effect
on oscillation frequency, it can be used to adjust R/F conversion accuracy. Oscillation waveforms and waveforms
output from the RFOUT terminal are shown in Figure 16.3.2.
RFIN0/1 terminal
RFOUT output
(Measurement counter clock)
V
DD
V
SS
V
DD
V
SS
3.2 Oscillation waveform
Figure 16.
(2) R/F conversion using an aC bias resistive sensor such as a humidity sensor
This conversion is possible only in channel 1, and this method is selected by setting ERF[1:0] to "2." This is basi-
cally the same as the R/F conversion described above (1), but the AC bias circuit works for a sensor (e.g. humidity
sensor) to which DC bias cannot be applied for a long time. The oscillating operation by reference resistance
is the same as the R/F conversion described above (1). Figure 16.3.3 shows the connection diagram of external
devices.
V
SS
SEN1
HUD
REF1
RFIN1
Channel 1
R
SEN
R
REF
C
RFC
R
SEN
:
R
REF
:
C
RFC
:
Resistive sensor (e.g. humidity sensor)
Reference resistor
Oscillating capacitor
3.3 Connection diagram of resistive humidity sensor
Figure 16.
The oscillation waveform is the same as Figure 16.3.2.