Operational Information
Recommended Xtal Components
V
DD
C
9
V
XTAL/CLOCK
XTAL
LOAD/LATCH
SERIAL ENABLE 1 –
DATA INPUTS
XTAL/CLOCK
1
1
2
3
D
5
D
4
D
3
D
2
D
1
D
0
Rx TONE DECODE OUTPUT
DECODE COMPARATOR INPUT
Rx TONE DETECT OUTPUT
NOTONE OUTPUT
SS
X
1
R
1
28
27
26
25
24
23
22
21
20
19
18
17
16
15
C
5
Rx TONE INPUT
PRIVATE ENABLE
Rx/Tx
CONTROL
PTL
FX375J
4
5
6
7
8
9
10
11
12
13
14
SERIAL ENABLE 2 –
SERIAL DATA INPUT –
SERIAL CLOCK INPUT –
C
2
C
1
XTAL
2
V
SS
C
3
C
4
Tx AUDIO INPUT
Rx AUDIO INPUT
Tx AUDIO OUTPUT
FX375J
Component
R
1
R
2
R
3
C
1
C
2
C
3
C
4
C
5
C
6
C
7
C
8
C
9
C
10
D
1
X
1
Unit Value
1M
820k
330k
33p
33p
0.1µ
0.1µ
0.1µ
1.0µ
0.1µ
1.0µ
1.0µ
1.0n
Small Signal
4MHz
Rx AUDIO OUTPUT
BALANCED MODULATOR INPUT
R
3
D
1
C
6
FILTER OUTPUT
Tx TONE OUTPUT
R
2
C
7
V
BIAS
C
8
C
10
V
SS
Fig.2 External Component Connections
Component Tolerances
Resistors
±
10%
Capacitors
±
20%
Operational Truth Table
–
Table 1 (below) illustrates the output paths and logic functions of the FX375 Private
Squelch Circuit in both Receive and Transmit modes.
Receive Operation –
(Rx/Tx = '1')
In the Rx mode Tx Tone and Tx Audio paths are held at bias.
D
0
– D
5
Tone
Tone
Tone
Notone
Tone
Tone
Tone
Notone
Notone
1
1
1
0
1
1
1
0
Private
Enable
0
0
0
0
1
1
1
1
PTL
1
0
X
X
1
0
X
X
Rx Tone
Detect
0
0
1
X
0
0
1
X
Rx Tone
Decode
1
1
0
0
1
1
0
0
Receive Signal Path
State
Condition
bias
open
open
open
bias
open
open
open
X
Not Inverted
Inverted
Not Inverted
X
Not Inverted
Not Inverted
Not Inverted
Transmit Operation –
(Rx/Tx ='0')
In the Tx mode the Rx audio path is held at bias and the Rx Tone Detect output at logic '0.'
D
0
– D
5
Tone
Tone
Notone
Tone
Tone
Notone
Notes
1.
2.
3.
4.
5.
6.
Notone
1
1
0
1
1
0
Private
Enable
0
0
0
1
1
1
PTL
1
0
X
1
0
X
Transmitted Tone
State
Phase
active
active
bias
active
active
bias
0°
180°
X
0°
180°
X
Transmit Signal Path
State
Condition
open
open
open
open
open
open
Inverted
Inverted
Not Inverted
Not Inverted
Not Inverted
Not Inverted
The pre- and de-emphasis circuits remain in the Transmit path during Clear and Private operation.
Power remains applied to the CTCSS tone decoder at all times.
Carrier Frequency = 3333Hz during Private operation (Tx or Rx).
During Clear operation the carrier frequency is turned off to reduce spurious emissions.
Under Rx-Notone conditions the Notone output can be used to operate squelch circuitry.
The functions in this table are applicable when the device is connected as recommended in Figure 2.
Table 1 Functions and Outputs
4
CMLMICRO [ CML MICROCIRCUITS ]
