SI3225-G-GQ Silicon Laboratories Inc, SI3225-G-GQ Datasheet - Page 69

• Manufacturer Part Number: SI3225-G-GQ
• Description: IC PROSLIC/CODEC DUAL 64TQFP
• Manufacturer: Silicon Laboratories Inc
• Series: ProSLIC®r

Specifications of SI3225-G-GQ

• Function: Subscriber Line Interface Concept (SLIC), CODEC
• Interface: GCI, PCM, SPI
• Number Of Circuits: 2
• Voltage - Supply: 3.3V, 5V
• Current - Supply: 65mA
• Power (watts): 941mW
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-TQFP, 64-VQFP
• Includes: Battery Switching, BORSCHT Functions, DTMF Generation and Decoding, FSK Tone Generation, Modem and Fax Tone Detection
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3.23. DTMF Detection
On-chip DTMF detection, also known as touch tone, is
available in the Si3220 and Si3225.
It is an in-band signaling system that replaces the pulse-
dial signaling standard. In DTMF, two tones generate a
DTMF digit. One tone is chosen from the four possible
row tones, and one tone is chosen from the four
possible column tones. The sum of these tones
constitutes one of 16 possible DTMF digits. The row
and column tones and corresponding digits are shown
in Table 39.
DTMF detection is performed using a modified Goertzel
algorithm to compute the DFT for each of the eight
DTMF frequencies and their second harmonics. At the
end of the DFT computation, the squared magnitudes of
the DFT results for the 8 DTMF fundamental tones are
computed. The row results are sorted to determine the
strongest row frequency, and the column frequencies
are sorted as well. Upon completion of this process,
checks are made to determine if the strongest row and
column tones constitute a DTMF digit.
I
BUF
Z
A
Figure 38. Pulse Metering Generation Block Diagram
+
+
Metering
Pulse
DAC
ADC
DAC
Oscillator
Metering
Pulse
x
+
Decimation
Rev. 1.3
Filter
The detection process occurs twice within the 45 ms
minimum tone time. A digit must be detected on two
consecutive tests after a pause to be recognized as a
new digit. If all tests pass, an interrupt is generated, and
the DTMF digit value is loaded into the DTMF register
according to Table 39. If tones occur at the maximum
rate of 100 ms per digit, the interrupt must be serviced
within 85 ms so that the current digit is not overwritten
by a new one. There is no buffering of the digit
information.
697 Hz
770 Hz
852 Hz
941 Hz
Volume
8 kHz
Table 39. DTMF Row/Column Tones
Si3220/25 Si3200/02
1209 Hz
1
4
7
*
PMRAMP
Logic
7FFF
Clip
or 0
±
+
Peak Detector
1336 Hz
2
5
8
0
12/16 kHz
Bandpass
–
1477 Hz
+
3
6
9
#
PMAMPTH
1633 Hz
C
D
A
B
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