mt88l85anr1 Zarlink Semiconductor, mt88l85anr1 Datasheet - Page 11

• Manufacturer Part Number: mt88l85anr1
• Description: 3 V Integrated Dtmf Transceiver With Power-down And Adaptive Micro Interface
• Manufacturer: Zarlink Semiconductor

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 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.
The Fourier components of the tone output correspond to V
harmonic distortion for a dual tone can be calculated by using Equation 2. V
amplitude and high group amplitude, respectively and V
internal switched-capacitor filter following the D/A converter keeps distortion products down to a very low level as
shown in Figure 9.
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
MT88L85
V
11
2
2
IMD
2f
+ V
2f
ACTUAL
1215.9
1331.7
1471.9
1645.0
V
.... V
is the sum of all the intermodulation components. The
699.1
766.2
847.4
948.0
2
2
fundamental
3f
+ V
nf
as measured on the output waveform. The total
2
4f
+ .... V
%ERROR
+0.30
+0.74
+0.57
+0.73
-0.49
-0.54
-0.32
-0.35
2
L
nf
and V
H
correspond to the low group
Data Sheet