SI3016-F-FS Silicon Laboratories Inc, SI3016-F-FS Datasheet - Page 19

• Manufacturer Part Number: SI3016-F-FS
• Description: IC ISOMODEM LINE-SIDE DAA 16SOIC
• Manufacturer: Silicon Laboratories Inc
• Type: Chipsetr

Specifications of SI3016-F-FS

• Package / Case: 16-SOIC (3.9mm Width)
• Data Format: V.90
• Baud Rates: 56k
• Interface: Serial
• Voltage - Supply: 3.3V, 5V
• Mounting Type: Surface Mount
• Product: Modem Chip
• Supply Current: 0.3 mA
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4.13. DTMF Dialing
In CTR21 dc termination mode, the DIAL bit should be
set during DTMF dialing if the LVCS[4:0] bits are less
than 12. Setting this bit increases headroom for large
signals. This bit should not be used during normal
operation or if the LVCS[4:0] bits are greater than 11.
In Japan dc termination mode, the system-side module
attenuates the transmit output by 1.7 dB to meet
headroom requirements. Similarly, in Low Voltage
termination mode, the system-side module attenuates
the transmit output by 4 dB. However, when DTMF
dialing is desired in these modes, this attenuation must
be removed. This is achieved by entering the FCC dc
termination mode and setting either the FJM or the
FLVM bits. When in the FCC dc termination modes,
these bits will enable the respective lower loop current
termination modes without the associated transmit
attenuation. Increased distortion may be observed,
which is acceptable during DTMF dialing. After DTMF
dialing is complete, the attenuation should be enabled
by returning to either the Japan dc termination mode
(DCT[1:0] = 01b) or the Low Voltage termination mode
(DCT[1:0] = 00b). The FJM and the FLVM bits have no
effect in any other termination mode other than the FCC
dc termination mode.
Higher DTMF levels may also be achieved if the
amplitude is increased and the peaks of the DTMF
signal are clipped at digital full scale (as opposed to
wrapping). Clipping the signal will produce some
distortion and intermodulation of the signal. Generally,
somewhat increased distortion (between 10–20%) is
acceptable during DTMF signaling. Several dB higher
DTMF levels can be achieved with this technique,
compared with a digital full-scale peak signal.
4.14. Pulse Dialing
Pulse dialing is accomplished by going off- and on-hook
to generate make and break pulses. The nominal rate is
10 pulses per second. Some countries have very tight
specifications for pulse fidelity, including make and
break times, make resistance, and rise and fall times. In
a traditional solid-state dc holding circuit, there are a
number of issues in meeting these requirements.
The Si3016 dc holding circuit has active control of the
on-hook and off-hook transients to maintain pulse
dialing fidelity.
Spark quenching requirements in countries, such as
Italy, the Netherlands, South Africa, and Australia deal
with the on-hook transition during pulse dialing. These
tests provide an inductive dc feed, resulting in a large
voltage spike. This spike is caused by the line
inductance and the sudden decrease in current through
the loop when going on-hook. The traditional way of
Rev. 1.0
dealing with this problem is to put a parallel RC shunt
across the hookswitch relay. The capacitor is large
(~1 µF, 250 V) and relatively expensive. In the Si3016,
the OHS bit can be used to slowly ramp down the loop
current to pass these tests without requiring additional
components.
4.15. Billing Tone Detection
“Billing tones” or “metering pulses” generated by the
central office can cause modem connection difficulties.
The billing tone is typically either a 12 kHz or 16 kHz
signal and is sometimes used in Germany, Switzerland,
and South Africa. Depending on line conditions, the
billing tone may be large enough to cause major errors
related to the modem data. The Si3016 has a feature
that allows the device to provide feedback as to whether
a billing tone has occurred and when it ends.
Billing tone detection is enabled by setting the BTE bit.
Billing tones less than 1.1 V
out by the low-pass digital filter on the Si3016. The ROV
bit is set when a line signal is greater than 1.1 V
indicating a receive overload condition. The BTD bit is
set when a line signal (billing tone) is large enough to
excessively reduce the line-derived power supply of the
line-side device (Si3016). When the BTD bit is set, the
dc termination is changed to an 800 Ω dc impedance.
This ensures minimum line voltage levels even in the
presence of billing tones.
The OVL bit should be polled following a billing tone
detection. When the OVL bit returns to zero, indicating
that the billing tone has passed, the BTE bit should be
written to zero to return the dc termination to its original
state. It will take approximately one second to return to
normal dc operating conditions. The BTD and ROV bits
are sticky, and they must be written to zero to be reset.
After the BTE, ROV, and BTD bits are all cleared, the
BTE bit can be set to re-enable billing tone detection.
Certain line events, such as an off-hook event on a
parallel phone or a polarity reversal, may trigger the
ROV or the BTD bits, after which the billing tone detector
must be reset. The user should look for multiple events
before qualifying whether billing tones are actually
present.
Although the DAA will remain off-hook during a billing
tone event, the received data from the line will be
corrupted when a large billing tone occurs. If the user
wishes to receive data through a billing tone, an external
LC filter must be added. A modem manufacturer can
provide this filter to users in the form of a dongle that
connects on the phone line before the DAA. This keeps
the manufacturer from having to include a costly LC filter
internal to the modem when it may only be necessary to
support a few countries/customers.
PK
on the line will be filtered
Si3016
PK
19
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