MT8889CP Zarlink Semiconductor, Inc., MT8889CP Datasheet - Page 11

• Manufacturer Part Number: MT8889CP
• Description: DTMF Transceiver, Integrated DTMF Transceiver with Adaptive Micro Interface
• Manufacturer: Zarlink Semiconductor, Inc.

8.0
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.
The Fourier components of the tone output correspond to V
harmonic distortion for a dual tone can be calculated 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.
9.0
The internal clock circuit is completed with the addition of a standard television colour burst crystal. The crystal
specification is as follows:
Frequency:
Frequency Tolerance:
Resonance Mode:
Load Capacitance:
Maximum Series Resistance:
Maximum Drive Level:
e.g.
A number of MT8889C devices can be connected as shown in Figure 13 such that only one crystal is required.
Alternatively, the OSC1 inputs on all devices can be driven from a TTL buffer with the OSC2 outputs left
unconnected.
Distortion Calculations
DTMF Clock Circuit
CTS Knights MP036S
Toyocom
TQC-203-A-9S
Figure 11 - Equation 1. THD (%) For a Single Tone
THD (%) = 100
THD (%) = 100
Figure 12 - Equation 2. THD (%) For a Dual Tone
3.579545 MHz
Parallel
18pF
150 ohms
2mW
0.1%
Zarlink Semiconductor Inc.
MT8889C
V
2
2L
V
V
+ V
2
2
11
3H
2
IMD
2f
2
+ .. V
V
2f
+ V
3L
2
.... V
is the sum of all the intermodulation components. The
V
L
+ .... V
2
fundamental
+ V
3f
2
nH
+ V
2
nf
H
+ V
2
2
nL
as measured on the output waveform. The total
4f
2
+ V
+ .... V
IMD
2
2H
2
+
L
nf
and V
H
correspond to the low group
Data Sheet