MT3170B/71B, MT3270B/71B, MT3370B/71B
be driven by an 4.194304 MHz external clock applied
on pin OSC 1. The OSC2 pin should be left open.
Parameter
Unit
Resonator
Crystal
R1
L1
Ohms
mH
pF
pF
-
6.580
0.359
4.441
34.890
25
For MT317xB devices , the CLK input is driven
directly by an 4.194304 MHz external digital clock.
95.355
15.1E-03
12.0
C1
C0
Qm
∆f
Applications
1.299E+03 101.2E+ 03
±0.2% ±0.01%
%
The circuit shown in Figure 3 illustrates the use of a
MT327xB in a typical receiver application. It requires
only a coupling capacitor (C1) and a crystal or
ceramic resonator (X1) to complete the circuit.
Table 4. Recommended Resonator and Crystal
Specifications
Note:
Qm=quality factor of RLC model, i.e., 1/2ΠƒR1C1.
The MT3x70B is designed for user who wishes to
tailor the guard time for specific applications. When
a DTMF signal is present, the ESt pin will go high.
An external microcontroller monitors ESt in real time
for a period of time set by the user. A guard time
algorithm must be implemented such that DTMF
signals not meeting the timing requirements are
rejected. The MT3x71B uses an internal counter to
provide a preset DTMF validation period. It requires
no external components. The DStD output high
indicates that a valid DTMF digit has been detected.
L1
C1
R1
C0
R1 = Equivalent resistor.
L1 = Equivalent inductance.
C1 = Equivalent compliance.
C0 = Capacitance between electrode.
Resonator and Crystal Electric Equivalent Circuit
Oscillator
The 4.194304 MHz frequency has a secondary
advantage in some applications where a real time
The MT327xB/337xB can be used in both external
clock or two pin oscillator mode. In two pin oscillator
mode, the oscillator circuit is completed by
connecting either a 4.194304 MHz crystal or ceramic
resonator across OSC1 and OSC2 pins.
Specifications of the ceramic resonator and crystal
are tabulated in Table 4. It is also possible to
configure a number of these devices employing only
a single oscillator crystal. The OSC2 output of the
first device in the chain is connected to the OSC1
input of the next device. Subsequent devices are
connected similarily. The oscillator circuit can also
clock is required.
4,194,304 cycles to provide a one second time base.
A 22-bit counter will count
VDD
C1
8
1
VDD
DTMF/CP Input
INPUT
MT327xB
7
6
2
3
OSC2
ESt/DStD
ACK
X1
To microprocessor or
microcontroller
OSC1
VSS
5
4
SD
COMPONENTS LIST:
C1 = 0.1 µF ± 10 %
X1 = Crystal or Resonator (4.194304 MHz)
Figure 3 - Application Circuit for MT327xB
4-7
MITEL [ MITEL NETWORKS CORPORATION ]
