Si3220/Si3225
Table 29. Recommended Values for Ring Trip Registers and RAM Addresses1
Ringing
Method
Ringing
DC
RTPER
RTACTH
RTDCTH
RTACDB/
RTDCDB
Frequency
Offset
Added?
Yes
No
800/fRING
800/fRING
2(800/
221 x RTPER
1.59 x VRING,PK x RTPER
0.577(RTPER x VOFF
)
)
16–32 Hz
33–60 Hz
32767
Internal
Yes
221 x RTPER
0.577(RTPER x VOFF
32767
(Si3220)
fRING
2(800/
fRING
)
See Note 2
No
Yes
Yes
1.59 x VRING,PK x RTPER
)
External
(Si3225)
16–32 Hz
33–60 Hz
800/fRING
2(800/
32767
32767
0.067 x RTPER x VOFF
0.067 x RTPER x VOFF
fRING
)
Notes:
1. All calculated values should be rounded to the nearest integer.
2. Refer to Ring Trip Debounce Interval for RTACDB and RTDCDB equations.
Table 30. Register and RAM Locations Used for Ring Trip Detection
Register/RAM
Register/RAM
Programmable
Resolution
Parameter
Mnemonic
Bits
Range
Ring Trip Interrupt Pending
Ring Trip Interrupt Enable
AC Ring Trip Threshold
DC Ring Trip Threshold
Ring Trip Sample Period
Linefeed Shadow (monitor only)
IRQVEC2
IRQEN2
RTACTH
RTDCTA
RTPER
RTRIPS
RTRIPE
RTACTH[15:0]
RTDCTH[15:0]
RTPER[15:0]
LFS[2:0]
Yes/No
Enabled/Disabled
See Table 29
See Table 29
See Table 29
N/A
N/A
N/A
LINEFEED
LCRRTP
N/A
N/A
Ring Trip Detect Status
RTP
N/A
(monitor only)
AC Ring Trip Detect Debounce
Interval
RTACDB
RTDCDB
ILOOP
RTACDB[15:0]
RTDCDB[15:0]
ILOOP[15:0]
0 to 40.96 s
0 to 40.96 s
1.25 ms
1.25 ms
DC Ring Trip Detect Debounce
Interval
Loop Current Sense
(monitor only)
0 to 101.09 mA
See
Table 20
Loop Closure Mask
Si3220 Ring Trip Detection
The Dual ProSLIC implements a loop closure mask to The Si3220 provides the ability to process a ring trip
ensure mode change between ringing and active or on- event using an ac-based detection scheme. Using this
hook transmission without causing an erroneous loop scheme eliminates the need to add dc offset to the
closure detection. The loop closure mask register, ringing signal, which reduces the total power dissipation
LCRMASK, should be set such that loop closure during the ringing state and maximizes the available
detection is ignored for the time (LCRMASK 1.25 ms/ ringing amplitude. This scheme is valid for shorter loop
LSB). The programmed time is set to mask detection of lengths only since it cannot reliably detect a ring trip
transitional currents that occur when exiting the ringing event if the off-hook line impedance overlaps the on-
mode while driving a reactive load (i.e., 5 REN). A hook impedance at 20 Hz.
typical setting is 80 ms (LCRMASK = 0x40).
52
Rev. 1.0
SILICONIMAGE [ Silicon image ]
