MT88L89 View Datasheet(PDF) - Mitel Networks

Part Name

Description

MFG CO.

MT88L89

3V Integrated DTMF Transceiver with Adaptive Micro Interface

Mitel Networks 

MT88L89

ACTIVE

INPUT

OUTPUT FREQUENCY (Hz)

SPECIFIED

ACTUAL

%ERROR

L1

697

699.1

+0.30

L2

770

766.2

-0.49

L3

852

847.4

-0.54

L4

941

948.0

+0.74

H1

1209

1215.9

+0.57

H2

1336

1331.7

-0.32

H3

1477

1471.9

-0.35

H4

1633

1645.0

+0.73

Table 2. Actual Frequencies Versus Standard

Requirements

Distortion Calculations

The MT88L89 is capable of producing precise tone

bursts with minimal error in frequency (see Table 2).

The internal summing amplifier is followed by a first-

order lowpass switched capacitor filter to minimize

harmonic components and intermodulation products.

The total harmonic distortion for a single tone can be

calculated using Equation 1, which is the ratio of the

total power of all the extraneous frequencies to the

power of the fundamental frequency expressed as a

percentage.

V22f + V23f + V24f + .... V2nf

THD (%) = 100

Vfundamental

Equation 1. THD (%) For a Single Tone

The Fourier components of the tone output

correspond to V2f.... Vnf as measured on the output

waveform. The total harmonic distortion for a dual

tone can be calculated using Equation 2. VL and VH

correspond to the low group amplitude and high

group amplitude, respectively and V2IMD is the sum

of all the intermodulation components. The internal

switched-capacitor filter following the D/A converter

keeps distortion products down to a very low level as

shown in Figure 10.

V22L + V23L + .... V2nL + V22H +

V23H + .. V2nH + V2IMD

THD (%) = 100

V2L + V2H

Equation 2. THD (%) For a Dual Tone

4-132

DTMF Clock Circuit

The internal clock circuit is completed with the

addition of a standard television colour burst crystal

having a resonant frequency of 3.579545 MHz. A

number of MT88L89 devices can be connected as

shown in Figure 11 such that only one crystal is

required. Alternatively, the OSC1 inputs on all

devices can be driven from a TTL buffer with the

OSC2 outputs left unconnected.

MT88L89

OSC1 OSC2

MT88L89

OSC1 OSC2

MT88L89

OSC1 OSC2

3.579545 MHz

Figure 11 - Common Crystal Connection

Microprocessor Interface

The MT88L89 design incorporates an adaptive

interface, which allows it to be connected to various

kinds of microprocessors. Key functions of this

interface include the following:

• Continuous activity on DS/RD is not necessary

to update the internal status registers.

• senses whether input timing is that of an Intel or

Motorola controller by monitoring the DS (RD),

R/W (WR) and CS inputs.

• generates equivalent CS signal for internal

operation for all processors.

• differentiates between multiplexed and non-

multiplexed microprocessor buses. Address

and data are latched in accordingly.

• compatible with Motorola and Intel processors.

Figure 16 shows the timing diagram for Motorola

microprocessors with separate address and data

buses. Members of this microprocessor family

include 2 MHz versions of the MC6800, MC6802 and

MC6809. For the MC6809, the chip select (CS) input

signal is formed by NANDing the (E+Q) clocks and

address decode output. For the MC6800 and

MC6802, CS is formed by NANDing VMA and

address decode output. On the falling edge of CS,

the internal logic senses the state of data strobe

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