DATA BULLETIN
MX315A
Features
Field Programmable Tone
Encoder
40 CTCSS Frequencies
Crystal-Controlled Frequency
Stability
Low Distortion Sinewave Output
Few External Components
Required
CMOS Low Power Requirements
CTCSS Encoder
Applications
Mobile Radio Base Stations & Repeater
Stations
Mobile Radios
Hand-Held Radios
Industrial Controls
Intercom Systems
Door-Entry Systems
Xtal/Clock
Clock
Generator
Xtal
D0-D5
Binary
Rate
Multiplier
Programmed Clocks
TX Tone
Sinewave
Output
Emitter
Follower
V
DD
TX Enable
TX Tone
Square
Wave
TX Tone Output
Enable
TX Enable
The MX315A is a monolithic CMOS tone encoder for sub-audible tone squelch systems, which provides three
additional frequencies over the earlier MX315A. These frequencies are 69.3, 97.4 and 206.5Hz. The tone
frequencies are derived from an input reference frequency. An on-chip inverter is provided to drive an
external crystal circuit.
Tone selection is achieved through six programming inputs and two control inputs (which allow either a logic
“1” or “0” to enable the device). A low distortion sinewave is generated at the TX Tone Output when the
MX315A is enabled. The emitter follower output stage can source 1mW directly into a 600 load (0dBm).
The MX315A is available in the following package styles: 16-pin SOIC (MX315ADW), 14-pin PDIP
(MX315AP) and 14-pin CDIP (MX315AJ).
1998 MXCOM, INC.
www.mxcom.com
tel: 800 638 5577 336 744 5050 fax: 336 744 5054
Doc. # 20480054.006
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All Trademarks and service marks are held by there respective companies.
CTCSS Encoder
2
MX315A
CONTENTS
Section
Page
1. Block Diagram................................................................................................................ 3
2. Signal List....................................................................................................................... 4
3. External Components.................................................................................................... 5
4. Application ..................................................................................................................... 6
4.1
4.2
Interfacing and Electromagnetic Capability ......................................................................... 6
CTCSS Programming.......................................................................................................... 7
5. Performance Specification............................................................................................ 8
5.1
Electrical Performance ........................................................................................................ 8
5.1.1
5.1.2
5.1.3
Absolute Maximum Ratings.................................................................................................... 8
Operating Limits ..................................................................................................................... 8
Operating Characteristics....................................................................................................... 8
5.2
Packaging............................................................................................................................ 9
MX•COM, Inc. reserves the right to change specifications at any time and without notice.
1998 MXCOM, INC.
www.mxcom.com
tel: 800 638 5577 336 744 5050 fax: 336 744 5054
Doc. # 20480054.006
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All Trademarks and service marks are held by there respective companies.
CTCSS Encoder
3
MX315A
1. Block Diagram
Clock
Generator
Xtal/Clock
Xtal
D0-D5
Binary
Rate
Multiplier
Programmed Clocks
TX Tone
Sinewave
Output
Emitter
Follower
V
DD
TX Enable
TX Tone
Square
Wave
TX Tone Output
Enable
TX Enable
Figure 1: Device Block Diagram
1998 MXCOM, INC.
www.mxcom.com
tel: 800 638 5577 336 744 5050 fax: 336 744 5054
Doc. # 20480054.006
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All Trademarks and service marks are held by there respective companies.
CTCSS Encoder
4
MX315A
2. Signal List
Pins
J,P
1
2
3
4
5
6
7
8
DW
1
2
3
4
5
6
7
8
Signal
Name
D3
D2
D1
D0
D4
D5
V
SS
Xtal/Clock In
Type
input
input
input
input
input
input
power
input
Negative Supply Voltage.
This is the input to the CMOS inverter. It can be used in
conjunction with the Xtal output to form the active element in a
crystal oscillator circuit. Alternatively, a logic level 1MHz
frequency can be injected at this pin. However, the supply
voltage should never be applied without the input clock signal.
This is the output of the CMOS inverter. When used as a
crystal oscillator, track lengths and loading of this pin should be
minimized.
Do not use
No Connection
No Connection
output
This is the tone output pin. It includes a low impedance emitter
follower stage for sourcing sinusoidal tone. The tone is
generated about a DC level of approximately V
DD
/2. The pin is
high impedance when not encoding.
This logic input has an internal pull-up resistor. A logic “0” at
this pin enables the MX315A.
This logic input has an internal pull-down resistor. A logic “1”
at this pin enables the MX315A.
Positive Supply Voltage.
Table 1: Signal List
D0-D5 are tone select inputs with internal pull-up resistors.
The logic combination at these inputs determines the encoded
CTCSS tone. See Table 1. The input sequence is not latched
and may be changed at any time. A logic “1” will be
programmed if the input is open circuit, allowing the use of
SPST switches.
Description
9
9
Xtal Output
output
10
10
11
12
Internal Connection
N/C
N/C
TX Tone Output
11
13
12
13
14
14
15
16
TX Enable Input
TX Enable Input
V
DD
input
input
power
1998 MXCOM, INC.
www.mxcom.com
tel: 800 638 5577 336 744 5050 fax: 336 744 5054
Doc. # 20480054.006
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All Trademarks and service marks are held by there respective companies.
CTCSS Encoder
5
MX315A
3. External Components
MICROPHONE
VOICE BAND
FILTER
SUMMING
AMPLIFIER
TO
MODULATOR
V
SS
4
8
X1
1MHz
33pF
1M
D0
3
2
1
D3
5
D4
6
D5
D1 D2
XTAL/CLOCK
9
XTAL
MX315AJ
11
TX TONE OUT
12
PTT
TX ENABLE
Figure 2: External Components
R1
C1
X1
Note 2, 3
Note 1
1M
33pF
1MHz
20%
20%
0.19%
Table 2: Recommended External Components
Notes:
1. The 1M resistor is used to bias the internal CMOS inverter into its linear mode. A tolerance of ±20%
is acceptable.
2. “X1” is a parallel resonant crystal. A reference frequency of 1MHz ±0.19% is required to maintain a
tone accuracy within 0.5%.
3. For best results, a crystal oscillator design should drive the clock inverter input with signal levels of at
least 40% of V
DD
, peak to peak. Tuning fork crystals generally cannot meet this requirement. To
obtain crystal oscillator design assistance, consult your crystal manufacturer.
1998 MXCOM, INC.
www.mxcom.com
tel: 800 638 5577 336 744 5050 fax: 336 744 5054
Doc. # 20480054.006
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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