MT88L85AN1 데이터 시트보기 (PDF) - Microsemi Corporation

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MT88L85AN1

3 V Integrated DTMF Transceiver with Power-Down and Adaptive Micro Interface

Microsemi Corporation 

MT88L85

Data Sheet

capable of issuing symmetric bursts/pauses of predetermined duration. This burst/pause duration is 51 ms±1 ms

which is a standard interval for autodialer and central office applications. After the burst/pause has been issued, the

appropriate bit is set in the Status Register to indicate that the transmitter is ready for more data. The timing

described above is available when DTMF mode has been selected. However, when CP mode (Call Progress mode)

is selected, the burst/pause duration is doubled to 102 ms ±2 ms. Note that when CP mode and Burst mode have

been selected, DTMF tones may only be transmitted and not received. In applications where a non-standard

burst/pause time is desirable, a software timing loop or external timer can be used to provide the timing pulses

when the burst mode is disabled by enabling and disabling the transmitter.

Single Tone Generation

A single tone mode is available whereby individual tones from the low group or high group can be generated. This

mode can be used for DTMF test equipment applications, acknowledgment tone generation and distortion

measurements. Refer to Control Register B (CRB) description for details.

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 MT88L85 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 by

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

V2fundamental

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 by 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 9.

11

Zarlink Semiconductor Inc.

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