PvtSQUELCHTM CTCSS Encoder/Decoder
5
MX375
Pin No.
Name
Type
Description
This pin is set internally to V /2. It must be externally decoupled using a
LH J,P,LH8
13
16
V
BIAS
DD
capacitor (C7) to V . See Figure 2.
SS
14
15
17
18
FILTER
OUTPUT
output This is the output of the Input Audio Bandpass Filter. It must be A.C.
coupled to the Balanced Modulator Input via capacitor C4. See Figure 2.
BALANCED
MODULATOR
INPUT
input
This is the input to the balanced modulator. Must be A.C. coupled to the
Filter Output via capacitor C4. See Figure 2.
16
19
RX AUDIO
OUTPUT
output Outputs the received audio from a buffered output stage and is held at
when in TX.
V
BIAS
17
18
19
20
20
21
22
23
TX AUDIO
OUTPUT
output Outputs the transmitted audio in TX. In RX, this pin is held at V
.
BIAS
RX AUDIO
INPUT
input
input
input
The audio input for the RX mode. Input signals should be AC coupled via
external capacitor C6. See Figure 2
TX AUDIO
INPUT
This is the TX Audio voice input. Signals should be AC coupled via
external capacitor C11. See Figure 2
The “press to listen” function input. In RX mode, a logic “0” enables the
RX Audio Output directly, overriding tone squelch but not intercepting a
private conversation; in TX mode, a logic “0” reverses the phase of the TX
Tone Output for “squelch tail” reduction (see Table 5).
PTL
21
24
CONTROL
RX/ TX
This input, together with Load/Latch, selects the operational mode of the
RX/ TX and PrivateEnable functions. See Table 5
22
23
25
26
input
input
This input selects the RX or TX mode (RX = 1, TX = 0). This can be
loaded in Serial or Parallel modes as described in Table 5
This input selects either Private or Clear mode (Clear = 1, Private = 0),
and can be loaded by Serial or Parallel modes as described in Table 5.
This input has an internal 1 MΩ pullup resistor.
PRIVATE
ENABLE
24
27
RX TONE
INPUT
This is the received audio input to the on-chip CTCSS tone decoder. It
should be A.C. coupled via capacitor C5.
Note: The MX375LH package is available in serial mode only.
Table 1: Signal List
© 1997 MX•COM Inc.
www.mxcom.com Tele: 800 638-5577 910 744-5050 Fax: 910 744-5054
Doc. # 20480026.007
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All trademarks and service marks are held by their respective companies.
CMLMICRO [ CML MICROCIRCUITS ]
