MT3170 datasheet(5/8 Pages) MITEL

5 / 8 page

MT3170B/71B, MT3270B/71B, MT3370B/71B

4-7

Table 4. Recommended Resonator and Crystal

Specifications

Note:

Qm=quality factor of RLC model, i.e., 1/2

ΠƒR1C1.

Resonator and Crystal Electric Equivalent Circuit

Oscillator

The MT327xB/337xB can be used in both external

clock or two pin oscillator mode. In two pin oscillator

mode,

the

oscillator

circuit

completed

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

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

Parameter

Unit

Resonator

Crystal

Ohms

6.580

0.359

95.355

4.441

15.1E-03

34.890

12.0

1.299E+03

101.2E+ 03

∆f

±0.2%

±0.01%

R1 = Equivalent resistor.

L1 = Equivalent inductance.

C1 = Equivalent compliance.

C0 = Capacitance between electrode.

be driven by an 4.194304 MHz external clock applied

on pin OSC 1. The OSC2 pin should be left open.

For MT317xB

devices , the CLK input is driven

directly by an 4.194304 MHz external digital clock.

Applications

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.

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.

The 4.194304 MHz frequency has a secondary

advantage in some applications where a real time

clock is required.

A 22-bit counter will count

4,194,304 cycles to provide a one second time base.

Figure 3 - Application Circuit for MT327xB

DTMF/CP Input

INPUT

OSC2

OSC1

VSS

VDD

ESt/DStD

ACK

VDD

COMPONENTS LIST:

C1 = 0.1 µF ± 10 %

X1 = Crystal or Resonator (4.194304 MHz)

To microprocessor or

microcontroller

MT327xB

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