SI3220-KQ Silicon Laboratories Inc, SI3220-KQ Datasheet - Page 50

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

Specifications of SI3220-KQ

• Package / Case: *
• 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: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Includes: Battery Switching, BORSCHT Functions, DTMF Generation and Decoding, FSK Tone Generation, Modem and Fax Tone Detection
• Product: Telecom
• Supply Voltage (min): 3.13 V
• Supply Current: 22 mA
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Number Of Channels: 2
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Si3220/Si3225
Ringing Relay Activation During Zero Crossings
The Si3225 is for applications that use a centralized
ringing generator and a per-channel ringing relay to
connect the ringing signal to the TIP/RING pair. The
Si3225 has one relay driver output per channel (RRDa
and RRDb) that can drive a mechanical or solid-state
DPDT relay. To reduce impulse noise that can couple
into adjacent lines, the relay should be closed when
there is zero voltage across the relay contacts and
opened during periods when there is zero current
through the contacts.
Closing the Relay at Zero Voltage
Internal voltage monitoring circuitry closes the relay at
zero voltage with respect to the line voltage. By
observing the phase of the ringing signal and constantly
monitoring the open-circuit T-R voltage, V
Si3225 can detect the next time when there is zero
voltage across the relay contacts.
Opening the Relay at Zero Current
Opening the ringing relay at zero current also is
accomplished using the internal monitoring circuitry and
prevents arcing from excess current flow when the relay
contacts are opened. The current flowing through the
ringing relay is continuously monitored in the IRNGNG
RAM address, and two internal counters (COUNTER0
and COUNTER1) detect time elapsed since the last two
zero current crossings based on the ringing period and
predict when the next zero crossing occurs. The ringing
relay current and internal counters are both updated at
an 8 kHz rate. To account for the mechanical delay of
the relay, a programmable advance firing timer allows
the user to initiate relay opening up to 10 ms prior to the
zero current crossing event. Figure 30 illustrates the
50
+
V
OFF
_
V
RING
806 kΩ
510 Ω
Si3225
806 kΩ
Figure 31. Si3225 External Ring Trip Circuitry
Si3200
Preliminary Rev. 0.91
OC
RING
TIP
, the
timing sequence for a typical ringing relay control
application.
During a typical ringing sequence, the Si3225 monitors
both the ringing relay current (IRNGNG) and the
RINGEN bit of the RINGCON register. The RINGEN bit
toggles because of pre-programmed ringing cadence or
a change in
COUNTER1 are re-started at each alternating zero
current
ZERDELAY equal to the ringing frequency period less
the desired advance firing time (D) is entered by the
user. If either counter reaches the same value as
ZERDELAY, the relay control signal is enabled when the
RINGEN bit transition has already occurred. During
typical ringing bursts, the LFS bits of the Linefeed
register toggle between the RINGING and OHT states
based on the pre-programmed ringing cadence. The
transition from OHT to RINGING is synchronized with
the RRD state transitions so the ringing burst starts
immediately. The transition from RINGING to OHT is
gated by a user-programmed delay period LFSDELAY
that ensures the ringing burst has ceased before going
to the OHT state or to the ACTIVE state in response to a
Linefeed state change.
Protection
crossing
operating
event,
state.
and
Relay
VDD
the
COUNTER0 and
Phone
delay
Switch
Hook
period