SI3225-BQ Silicon Laboratories Inc, SI3225-BQ Datasheet - Page 44
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SI3225-BQ
Manufacturer Part Number
SI3225-BQ
Description
IC SLIC/CODEC DUAL-CH 64TQFP
Manufacturer
Silicon Laboratories Inc
Series
ProSLIC®r
Specifications of SI3225-BQ
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
-40°C ~ 85°C
Mounting Type
Surface Mount
Includes
Battery Switching, BORSCHT Functions, DTMF Generation and Decoding, FSK Tone Generation, Modem and Fax Tone Detection
Product
SLIC
Supply Voltage (min)
3.13 V
Supply Current
22 mA
Maximum Operating Temperature
+ 85 C
Minimum Operating Temperature
- 40 C
Mounting Style
SMD/SMT
Number Of Channels
2
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
SI3225-BQ
Manufacturer:
Silicon Laboratories Inc
Quantity:
10 000
Si3220/Si3225
Ring Trip Detection
A ring trip event signals that the terminal equipment has
transitioned to an off-hook state after ringing has
commenced, ensuring that the ringing signal is removed
before normal speech begins. The Dual ProSLIC is
designed to implement either an ac- or dc-based
internal ring trip detection scheme or a combination of
both schemes. The system design is flexible to address
varying loop lengths of different applications. An ac ring
trip detection scheme cannot reliably detect an off-hook
condition when sourcing longer loop lengths, as the
20 Hz ac impedance of an off-hook long loop is
indistinguishable from a heavily loaded (5 REN) short
loop in the on-hook state. Therefore, a dc ring trip
detection scheme is required when sourcing longer loop
lengths.
The Si3220 can implement either an ac- or dc-based
ring trip detection scheme, depending on the application.
The Si3225 allows external dc ring trip detection when
using a battery-backed external ringing generator by
monitoring the ringing feed path through two sensing
inputs on each channel. By monitoring this path, the
Dual ProSLIC detects a dc current flowing in the loop
once the end equipment has gone off-hook. Table 26
provides recommended register and RAM settings for
various applications, and Table 27 lists the register and
RAM addresses that must be written or monitored to
correctly detect a ring trip condition.
Figure 27 illustrates the internal functional blocks that
correctly detect and process a ring trip event. The
primary input to the system is the loop current sense
(ILOOP) value provided by the loop monitoring circuitry
and reported in the ILOOP RAM location register. The
ILOOP RAM location value is processed by the ISP
block when the LFS bits in the Linefeed register indicate
the device is in the ringing state. The output of the ISP
then feeds into a pair of programmable digital low-pass
filters; one for the ac ring trip detection path and one for
44
Preliminary Rev. 0.91
the dc path. The ac path also includes a full wave
rectifier block prior to the LPF block. The outputs of
each low pass filter block are then passed on to a
programmable ring trip threshold (RTACTH for ac
detection and RTDCTH for dc detection). Each
threshold block output is then fed to a programmable
debounce filter to ensure a valid ring trip event. The
output of each debounce filter remains constant unless
the input remains in the opposite state for the entire
period of time set using the ac and dc ring trip debounce
interval registers, RTACDB and RTDCDB, respectively.
The outputs of both debounce filter blocks are then
ORed together. If either the ac or the dc ring trip circuits
indicate a valid ring trip event has occurred, the RTP bit
is set. Either the ac or dc ring trip detection circuits are
disabled by setting the respective ring trip threshold
sufficiently high so that it does not trip under any
condition. A ring trip interrupt also generates if the
RTRIPE bit is enabled.
Ringtrip Timeout Counter
The Dual ProSLIC incorporates a ringtrip timeout
counter (RTCOUNT) that will monitor the status of the
ringing control. When exiting ringing, the Dual ProSLIC
will allow the ringtrip timeout counter amount of time
(RTCOUNT x 1.25 ms/LSB) for the mode to switch to
On-hook Transmission or Active. The mode that is
being exited to is governed by whether the command to
exit ringing is a ringing active timer expiration (on-hook
transmission) or ringtrip/manual mode change (Active
mode). The ringtrip timeout counter will assure ringing is
exited within its time setting (RTCOUNT x 1.25 ms/LSB,
typically 200 ms).
Ringtrip Debounce Interval
The ac and dc ring trip debounce intervals can be
calculated based on the following equations:
RTACDB = t
RTDCDB = t
debounce
debounce
(1600/RTPER)
(1600/RTPER)