DATA BULLETIN
MX375
Features
•
PRIVATE/CLEAR CAPABILITY
•
ON-CHIP TX AUDIO PRE/DEEMPHASIS
•
ALTERNATIVE TO STANDARD CTCSS
“PARTY LINE”
•
POWERSAVE OPTION
Pvt
SQUELCH
TM
CTCSS
Encoder/Decoder
Applications
•
MOBILE RADIOS
•
COMMUNITY REPEATERS
•
TELEPHONE/RADIO INTERCONNECT
SYSTEMS
TX
TX Audio
Input
6dB/Octave
TX
Filter
Output
Balanced
Modulator
CLR
Input
-6dB/Octave
TX Audio Output
RX
BIAS
RX
RX Audio
Input
XTAL
XTAL
RX Tone Input
Load/Latch
D5 or Serial Enable 1
D4 or Serial Enable 2
D3 or Serial Data Input
D2 or Serial Clock Input
D1 Input
D0 Input
RX/TX
Control
Private Enable
Push-To-Listen
PTL
8-Bit
Shift
Register
and
Latches
LD5-LD0
Logic
Control
f
CARRIER
NoTone Output
f
CLK1
V
DD
f
CLK2
f
EMPH
RX Path
V
BIAS
TX Path
Private
V
SS
f
EMPH
f
CLK1
f
CARRIER
f
CLK2
f
EMPH
PVT
BIAS
TX
RX Audio Output
3333Hz
Reference
Hysteresis
Clocks
Filters
RX Tone Decoder Output
Decode Comparator Input
RX Tone Detect Output
CTCSS
Tone Detect
3333 Hz
TX Tone
Output
The MX375 is a CMOS LSI microcircuit which combines CTCSS Encode/Decode operation with voice band frequency
inversion. Frequency inversion is achieved by modulating the input audio with a 3333 Hz carrier frequency. Higher voice
band frequencies are translated downward, and lower frequencies upward, resulting in a “mirror image” voice
transmission.
PvtSQUELCH™
combines CTCSS with inverted speech to prevent users from understanding each other’s
communications unless the transmissions are accompanied by the group’s assigned tone. Its net effect is to eliminate
casual eavesdropping and give mobile radio users a certain degree of privacy at a minimal price. Up to 38
PvtSQUELCH
user groups (one per CTCSS tone) can share a single radio channel. With
PvtSQUELCH,
competing businesses can
share a radio channel without compromising communications security.
Device features: 1) serial or parallel tone programming capability (serial or parallel offered on MX375J, P & LH8), 2) the
ability to operate under NOTONE conditions, 3) on-chip Tx and Rx audio filtering, 4) pin-selectable Private/Clear
operation, and 5) pre/deemphasis filters in the Tx path, for optimal recovered audio quality.
A low-cost 4 MHz crystal/clock and a single 5V supply are required for operation. The MX375 is available in the following
package styles: 28-pin PDIP (MX375P), 28-pin CDIP (MX375J) 28-pin PLCC (MX375LH8), and
24-pin PLCC (MX375LH).
© 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 ]
