2 mask option, When "use" is selected – Epson S1C63558 User Manual
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138
EPSON
S1C63558 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (FSK Demodulator)
4.15.2 Mask option
The gain of the input amplifier shown in Figure 4.15.1.2 is fixed at 1 (0dB) when the internal feedback
resistor is used.
Use of this internal feedback resistor can be selected by mask option.
When "Use" is selected:
TIP
40k
Ω
40k
Ω
100k
Ω
100k
Ω
V
REF
V
REF
100k
Ω
100k
Ω
Amp
–
+
RING
FB
Fig. 4.15.2.1 Circuit configuration when the internal feedback resistor is used
The gain is fixed at 1 (0dB). Leave the FB terminal open.
When "Not use" is selected (example of differential input):
TIP
Amp
–
+
RING
FB
R
5
R
3
R
6
R
4
R
1
R
2
V
REF
V
REF
500pF
500pF
Fig. 4.15.2.2 Circuit configuration when the internal feedback resistor is not used (example of differential input)
The gain of the amplifier can be changed with external resistors.
A 500 k
Ω
resistor is recommended for R
1
, R
2
, R
5
and R
6
, and approximately 200 k
Ω
for R
3
and R
4
.
The gain can be found with the following formula.
G
Amp
=
R
5
=
R
6
(In case of R
1
= R
2
, R
3
= R
4
, R
5
= R
6
)
R
1
R
2
When "Not use" is selected (example of single-end input):
TIP
Amp
–
+
RING
FB
R
F
R
IN
V
REF
500pF
Fig. 4.15.2.3 Circuit configuration when the internal feedback resistor is not used (example of single-end input)
The gain of the amplifier can be changed with external resistors.
A resistor of approximately 500 k
Ω
is recommended for R
IN
and R
F
.
The gain can be found with the following formula.
G
Amp
=
R
F
R
IN