DATA BULLETIN
MX014
Features
•
CTCSS Compatible
•
Fixed Frequency Inversion
•
Low Power CMOS
Voice Band inverter
Applications
•
Land Mobile Radio Systems
•
Community Repeaters
BALMOD
DEEMP Out
RX Buffer In
TX Audio Feedback
TX Audio In
6dB/Octave
Pre-emphasis
10dB Gain
Rx Path
Path Invert
TX Buffer In
BPF Out
Filter
TX
6dB/Octave
De-emphasis
TX Audio Out
TX
BIAS
RX Audio In
Bandpass
Filter
300-3033 Hz
Bandpass
Filter
300-3033 Hz
Filsav 1
BIAS
RX Path
Filsav 1
RX Path
Carrier
RX Audio Out
Filsav 2
RX Audio Feedback
3333 Hz
PTT
PTT
RX Audio Enable
RX Audio Enable
PTL
PTL
Privacy Enable
Clock
Carrier
Filsav 1
Filsav 2
CLK
3333 Hz
CLK Generator
Clock
LOGIC
RX Path
EMPSAV
TX
Path Invert
V
DD
V
SS
BIAS
The MX014 Voice Band Inverter gives the security of private voice communications to land mobile radio users, as well as
to the users of other shared radio channel systems. Designed for use in half-duplex systems, the MX014 exchanges high
and low frequencies in the voiceband and renders transmitted messages unintelligible. This privacy function is achieved
by a single frequency inversion. When used with CTCSS,
PvtSQUELCH
TM
privacy adapter operation is achieved.
Sharp cut-off in the internal voiceband filters permits operation with CTCSS and similar sub-audio signaling schemes. This
results in high quality recovered audio.
The core of the MX014 consists of two audio band pass filters and a balanced modulator. The device uses a
programmable clock divider which controls the carrier and filter cut-off frequencies. Control of the RX/TX, PTL and
privacy function is by pin selection.
The MX014 operates from a single 5V supply and uses a 4 MHz crystal oscillator to ensure the correct pitch in recovered
speech. Signal coupling and decoupling are the only external components needed. The device is available in 24-pin
PLCC (MX014LH), 24-pin PDIP (MX014P) and 24-pin CDIP (MX014J) packages.
©
1997 MX•COM, INC.
www.mxcom.com Tele: 800 638 5577 910 744 5050 Fax: 910 744 5054
Doc. # 20480013.006
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All trademarks and service marks are held by there respective companies.
Voice Band Inverter
2
MX014
CONTENTS
Section
Page
1. Block Diagram .................................................................................................................................. 3
2. Signal List ......................................................................................................................................... 4
3. External Components ...................................................................................................................... 5
4. Application ....................................................................................................................................... 6
5. Performance Specification.............................................................................................................. 8
5.1 Electrical Performance .............................................................................................................................. 8
5.1.1 Absolute Maximum Ratings ...............................................................................................................................8
5.1.2 Operating Limits.................................................................................................................................................8
5.1.3 Operating Characteristics ..................................................................................................................................8
5.2 Packaging ................................................................................................................................................ 10
MX•COM, Inc. reserves the right to change specifications at any time and without notice.
©
1997 MX•COM, INC.
www.mxcom.com Tele: 800 638 5577 910 744 5050 Fax: 910 744 5054
Doc. # 20480013.006
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All trademarks and service marks are held by there respective companies.
Voice Band Inverter
3
MX014
1. Block Diagram
BALMOD
DEEMP Out
RX Buffer In
TX Buffer In
BPF Out
Filter
TX Audio Feedback
TX Audio In
6dB/Octave
Pre-emphasis
10dB Gain
Rx Path
Path Invert
TX
6dB/Octave
De-emphasis
TX Audio Out
TX
BIAS
RX Audio In
Bandpass
Filter
300-3033 Hz
Bandpass
Filter
300-3033 Hz
Filsav 1
BIAS
RX Path
Filsav 1
RX Path
Carrier
RX Audio Out
Filsav 2
RX Audio Feedback
3333 Hz
PTT
PTT
RX Audio Enable
RX Audio Enable
PTL
PTL
Privacy Enable
Clock
Carrier
Filsav 1
Filsav 2
CLK
3333 Hz
CLK Generator
Clock
LOGIC
RX Path
EMPSAV
TX
Path Invert
V
DD
V
SS
BIAS
Figure 1: Device Block Diagram
©
1997 MX•COM, INC.
www.mxcom.com Tele: 800 638 5577 910 744 5050 Fax: 910 744 5054
Doc. # 20480013.006
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All trademarks and service marks are held by there respective companies.
Voice Band Inverter
4
MX014
2. Signal List
Pin No.
1
2
3
4
5
6
7
8
9
Name
XTAL
Description
An external 4MHz clock can be applied to this input. The clock circuit on chip has a resistor
and capacitors so that only one external crystal is required.
This is the inverted 4MHz clock output for use when a crystal oscillator is used, or as a buffer
for driving other clocked devices.
Push To Talk is an input with a 3MΩ pull-down resistor.
This is the inverted PTT output. It has a 100kΩ output impedance.
Push To Listen is an input with a 3MΩ pull-down resistor.
XTAL
PTT
PTT
PTL
PTL
RXAUDEN
Push To Listen
is the inverted output of PTL; it has a 100kΩ output impedance.
RX Audio Enable is an input with a 3MΩ pull-down resistor.
RXAUDEN
PRIVEN
RX Audio Enable
is the inverted output of RX Audio Enable; it has a 100kΩ output impedance.
Privacy Enable controls the input action of the balanced modulator by switching the carrier
clock. When audio signals are inverted, the signal path gain is adjusted automatically to
compensate for the upper sideband loss. It contains a 3MΩ pull-down resistor.
This is the receive audio output pin. It is biased at V
DD
/2 when in the TX mode.
This is the “send” voice output pin. It is biased at V
DD
/2 when in RX mode.
The negative supply pin (ground).
For a gain of one in the RX Output stage, these two pins are wire linked together. However,
if gain is introduced at the RX input, attenuation may be introduced at the RX Output using
these pins and two resistors.
The pre-emphasis circuit has a 10dB gain at 1 kHz. Additional gain, or attenuation can
be introduced as in the RX path.
This is the internally generated V
DD
/2 decoupling pin.
This filter is the output of the Input Audio BPF and must be a.c. coupled into the Balanced
Modulator Input through a 0.1µF capacitor.
This is the input to the balanced modulator. It must be a.c. coupled to the Filter Output.
This is a negative input of an op-amp at the input of the RX path. It can be used, along with
RX Audio Feedback and two external resistors, to increase the signal to its optimum level prior
to frequency inversion/filtering. This may improve the S/N.
RX Audio Feedback is the output of an op-amp at the input of the RX path. See RXIN.
The negative input of an op-amp at the input of the TX path. It can be used, along with TX
Audio Feedback and two external resistors, to increase the signal to its optimum level prior to
frequency inversion/filtering. This may improve S/N.
TX Audio Feedback is the output of an op-amp at the input of the TX path. See TXIN.
The positive supply pin.
Table 1: Signal List
10
11
12
13
14
15
16
17
18
19
20
RXOUT
TXOUT
V
SS
BPFOUT
RXBIN
DEMPOUT
TXBIN
BIAS
FILTR
BALMOD
RXIN
21
22
RXFB
TXIN
23
24
TXFB
V
DD
©
1997 MX•COM, INC.
www.mxcom.com Tele: 800 638 5577 910 744 5050 Fax: 910 744 5054
Doc. # 20480013.006
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All trademarks and service marks are held by there respective companies.
Voice Band Inverter
5
MX014
3. External Components
Configuration for Radios with
Existing Pre- and De-emphasis.
1 XTAL
MX014
V
DD
2 XTAL
TXFB
3 PTT
TXIN
4
RXFB
PTT
5 PTL
RXIN
6 PTL
BALMOD
7 RXAUDEN
FILTR
8 RXAUDEN
BIAS
9
TXBIN
PRIVEN
10 RXOUT DEMPOUT
11 TXOUT
RXBIN
12
V
SS
BPFOUT
24
23
22
21
20
19
18
17
16
15
14
13
C4
R7
R5
R8
R6
R1
R3
For Use in Radios without
Pre- and De-emphasis.
1 XTAL
MX014
V
DD
2 XTAL
TXFB
3 PTT
TXIN
4
RXFB
PTT
5 PTL
RXIN
6 PTL
BALMOD
7 RXAUDEN
FILTR
8 RXAUDEN
BIAS
9
TXBIN
PRIVEN
10 RXOUT DEMPOUT
11 TXOUT
RXBIN
12
V
SS
BPFOUT
24
23
22
21
20
19
18
17
16
15
14
13
R11
R9
C4
R10
R12
Bias
Bias
R1
R3
X1
V
DD
C1
R2
C2
R4
C3
TX Channel
RX Channel
X1
V
DD
C1
R2
C2
R4
C3
TX Channel
RX Channel
Bias
Bias
Figure 2: External Components Connections
R8
R7
+
R8
R6
R5
+
R6
R10
R9
+
R10
R12
R11
+
R12
TX Attenuation
=
TX Attenuation
=
For a gain of 1, R8
= ∞
, R7
=
0
RX Attenuation
=
For a gain of 1, R9
=
0, R10
= ∞
RX Attenuation
=
For a gain of 1, R6
= ∞
, R5
=
0
For a gain of 1, R11
=
0, R12
= ∞
Table 2: Gain and Attentuation Calculations
Recommended External Component Notes:
1. Component Values: C1- C3 = 0.1 µF, C4 = 1.0 µF, X1 = 4 MHz crystal
2. R1 to R12 values will depend on the configuration and the gain or attenuation required. However R1, R3, R5, R7,
and R11 should be 100 kΩ or greater. To add gain or attenuate, use R5-R12 as shown. See pin descriptions for
more information.
3. For best results, a crystal oscillator design should drive the clock inverter input with signal levels of at least 40% of
VDD, peak to peak. Tuning fork crystals generally cannot meet this requirement. To obtain crystal oscillator
design assistance, consult your crystal manufacturer.
©
1997 MX•COM, INC.
www.mxcom.com Tele: 800 638 5577 910 744 5050 Fax: 910 744 5054
Doc. # 20480013.006
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All trademarks and service marks are held by there respective companies.
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