MT8889CSR Zarlink Semiconductor, Inc., MT8889CSR Datasheet - Page 7

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MT8889CSR

Manufacturer Part Number
MT8889CSR
Description
Integrated DTMF Transceiver with Adaptive Micro Interface
Manufacturer
Zarlink Semiconductor, Inc.
Datasheet

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Burst Mode
In certain telephony applications it is required that
DTMF signals being generated are of a specific
duration
application or by any one of the exchange transmitter
specifications currently existing. Standard DTMF
signal timing can be accomplished by making use of
the Burst Mode. The transmitter is 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
indicating 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 be transmitted only 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
generation and distortion measurements. Refer to
Control Register B description for details.
determined
applications,
either
acknowledgment
by
the
particular
Figure 10 - Spectrum Plot
tone
Distortion Calculations
The MT8889C 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.
Scaling Information
10 dB/Div
Start Frequency = 0 Hz
Stop Frequency = 3400 Hz
Marker Frequency = 697 Hz and
1209 Hz
Table 2. Actual Frequencies Versus Standard
THD (%) = 100
ACTIVE
INPUT
L1
L2
L3
L4
H1
H2
H3
H4
Equation 1. THD (%) For a Single Tone
OUTPUT FREQUENCY (Hz)
SPECIFIED
1209
1336
1477
1633
697
770
852
941
Requirements
V
2
2f
+ V
ACTUAL
1215.9
1331.7
1471.9
1645.0
V
699.1
766.2
847.4
948.0
2
fundamental
3f
+ V
MT8889C
2
4f
+ .... V
%ERROR
+0.30
+0.74
+0.57
+0.73
-0.49
-0.54
-0.32
-0.35
2
nf
7

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