SI3220-GQ Silicon Laboratories Inc, SI3220-GQ Datasheet - Page 48

• Manufacturer Part Number: SI3220-GQ
• Description: IC SLIC/CODEC DUAL-CH 64TQFP
• Manufacturer: Silicon Laboratories Inc
• Series: ProSLIC®r

Specifications of SI3220-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: *
• 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

Si3220/Si3225
Internal Sinusoidal Ringing
A sinusoidal ringing waveform is generated by the on-
chip digital tone generator. The tone generator used to
generate ringing tones is a two-pole resonator with a
programmable frequency and amplitude. Since ringing
frequencies are low compared to the audio band
signaling frequencies, the sinusoid is generated at a
1 kHz rate. The ringing generator is programmed via the
RINGFREQ, RINGAMP, and RINGPHAS registers. The
equations are as follows:
For example, to generate a 60 V
ringing signal, the equations are as follows:
In addition to the variable frequency and amplitude, a
selectable dc offset (V
waveform, is included. The dc offset is defined in the
RINGOF RAM location.
As with the tone generators, the ringing generator has
two timers which function as described above. They
allow on/off cadence settings up to 8 s on/8 s off. In
addition to controlling ringing cadence, these timers
control the transition into and out of the ringing state.
To initiate ringing, the user must program the
RINGFREQ,
addresses as well as the RINGTA and RINGTI registers
and select the ringing waveshape and dc offset. After
this is done, TAEN and TIEN bits are set as desired.
The ringing state is invoked by a write to the linefeed
register. At the expiration of RINGTA, the Dual ProSLIC
turns off the ringing waveform and goes to the on-hook
transmission state. At the expiration of RINGTI, ringing
is initiated again. This process continues as long as the
two timers are enabled and the linefeed register
remains in the ringing state.
48
RINGAMP
RINGAMP
RINGFREQ
0x7EFD9D
=
coeff
1
-- -
4
coeff
RINGFREQ = coeff
RINGAMP,
=
-------------------- -
1.99211
00789
=
1
-- - 1 coeff
4
=
RINGPHAS
=
0.9921
cos
----------------------- -
1
OFF
cos
+
–


coeff
×
-------------------- -
1000Hz
), which can be added to the


(
2π20
-------------------- -
1000Hz
×
2
15
(
and
2πf
2
×
)
23
×
(
=
2


)
-------------------- -
160.173
15
=
×
0


=
rms
2
)
RINGPHAS
0.9921
85
23
8322461
×
DesiredV
---------------------------------
(87 V
160.173V
=
273
PK
=
=
), 20 Hz
PK
0x111
RAM
Rev. 1.0
Internal Trapezoidal Ringing
In
waveform, the Dual ProSLIC can generate a trapezoidal
ringing waveform similar to the one illustrated in
Figure 26 on page 49. The RINGFREQ, RINGAMP, and
RINGPHAS RAM addresses are used for programming
the ringing wave shape as follows:
RINGPHAS = 4 x Period x 8000
RINGAMP = (Desired V/160.8 V) x (2
RINGFREQ = (2 x RINGAMP)/(t
RINGFREQ is a value that is added or subtracted from
the waveform to ramp the signal up or down in a linear
fashion. This value is a function of rise time, period, and
amplitude, where rise time and period are related
through the following equation for the crest factor of a
trapezoidal waveform.
where
So, for a 90 V
crest factor of 1.3, the period is 0.05 s, and the rise time
requirement is 0.015 s.
RINGPHAS = 4 x 0.05 x 8000 = 1600 (0x0640)
RINGAMP = 90/160.8 x (2
RINGFREQ = (2 x RINGAMP)/(0.0153 x 8000) = 300
(0x012C)
The time registers and interrupts described in the
sinusoidal ring description also apply to the trapezoidal
ring waveform:
Internal Unbalanced Ringing
The Si3220 also provides the ability to generate a
traditional battery-backed unbalanced ringing waveform
for ringing terminating devices that require a high dc
content or for use in ground-start systems that cannot
tolerate a ringing waveform on both the TIP and RING
leads. The unbalanced ringing scheme applies the
ringing signal to the RING lead; the TIP lead remains at
the programmed VCM voltage that is very close to
ground. A programmable dc offset can be preset to
provide dc current for ring trip detection. Figure 25
illustrates the internal unbalanced ringing waveform.
addition
to
PK
T
CF
, 20 Hz trapezoidal waveform with a
=
t
RISE
the
=
Period
desired crest factor
=
traditional
3
-- - T 1
4
15
=
) = 18340 (0x47A5)


------------- -
f
RING
–
1
RISE
---------- -
CF
1
2
sinusoidal


x 8000)
15
)
ringing