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.
CMLMICRO [ CML MICROCIRCUITS ]
