Table of Contents
Advertisement
11.3
Operation
11.3.1
Output Waveform
The DTMF generator outputs a row-group or column-group sine wave (DTMF signal) or a
combined row-column waveform at the TONED pin. These signals are generated by a high-
precision resistor-ladder-type D/A converter circuit. The output frequency is selected by DTCR.
Figure 11.3 shows an equivalent circuit for the TONED output. Figure 11.4 shows the output
waveform of an independent row-group or column-group signal. One cycle of the output is
divided into 32 segments, giving a stable output with low distortion.
Output
control
VT
ref
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
GND
Figure 11.4 TONED Output Waveform (Independent Row- or Column-Group Output)
Control
Figure 11.3 Equivalent Circuit for TONED Output
Row
Column
Time slot
VT
ref
GND
TONED
277
Advertisement
Table of Contents
