mt8885an1 Zarlink Semiconductor, mt8885an1 Datasheet - Page 11

• Manufacturer Part Number: mt8885an1
• Description: Integrated Dtmf Transceiver With Power-down And Adaptive Micro Interface
• Manufacturer: Zarlink Semiconductor

6.0
The MT8885 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 10.
Distortion Calculations
Table 2 - Actual Frequencies Versus Standard Requirements
Active
Input
H1
H2
H3
H4
L1
L2
L3
L4
THD (%) = 100
THD (%) = 100
Equation 1. THD (%) For a Single Tone
Equation 2. THD (%) For a Dual Tone
Specified
Output Frequency (Hz)
1209
1336
1477
1633
697
770
852
941
Zarlink Semiconductor Inc.
MT8885
V
2
2L
V
V
11
2
+
2
2
IMD
3H
2f
V
2
+ V
V
2f
+ ..
3L
V
2
.... V
is the sum of all the intermodulation components. The
L
2
+ ....
2
V
+
fundamental
1215.9
1331.7
1471.9
1645.0
3f
Actual
699.1
766.2
847.4
948.0
2
V
nH
+ V
nf
2
V
H
+
as measured on the output waveform. The total
2
2
nL
V
4f
2
+
IMD
+ .... V
V
2
2H
+
2
L
nf
and V
%Error
+0.30
+0.74
+0.57
+0.73
-0.49
-0.54
-0.32
-0.35
H
correspond to the low group
Data Sheet