mt88l89asr1 Zarlink Semiconductor, mt88l89asr1 Datasheet - Page 10

• Manufacturer Part Number: mt88l89asr1
• Description: 3 V Integrated Dtmf Transceiver With Adaptive Micro Interface
• Manufacturer: Zarlink Semiconductor

Burst Mode
In certain telephony applications it is required that DTMF signals being generated are of a specific duration
determined either by the particular 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 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.
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 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.
Table 2 - Actual Frequencies Versus Standard Requirements
THD (%) = 100
Active
Input
H1
H2
H3
H4
L1
L2
L3
L4
Equation 1. THD (%) For a Single Tone
Output Frequency (Hz)
Specified
Zarlink Semiconductor Inc.
1209
1336
1477
1633
697
770
852
941
MT88L89
V
10
2
2f
+ V
Actual
1215.9
1331.7
1471.9
1645.0
V
699.1
766.2
847.4
948.0
2
2
fundamental
3f
+ V
2
4f
+ .... V
%Error
+0.30
+0.74
+0.57
+0.73
-0.49
-0.54
-0.32
-0.35
2
nf
Data Sheet