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

Data Sheet

6

Zarlink Semiconductor Inc.

Table 4 - Recommended Resonator and Crystal Specifications

Note:

Qm=quality factor of RLC model, i.e., 1/2P¶R1C1.

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 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 similarly. The

oscillator circuit can also 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.

Parameter

Unit

Resonator

Crystal

R1

Ohms

6.580

150

L1

mH

0.359

95.355

C1

pF

4.441

15.1E-03

C0

pF

34.890

12.0

Qm

-

1.299E+03

101.2E+ 03

∆f

%

±0.2%

±0.01%

R1 = Equivalent resistor.

L1 = Equivalent inductance.

C1 = Equivalent compliance.

C0 = Capacitance between electrode.

L1

C1

R1

C0