SI3211 ETC, SI3211 Datasheet - Page 22

• Manufacturer Part Number: SI3211
• Description: PROSLIC PROGRAMMABLE CMOS SLIC/CODEC WITH RINGING/BATTERY VOLTAGE GENERATION
• Manufacturer: ETC

Si 3210/ Si3 211/S i32 12
Linefeed Architecture
The ProSLIC is a low-voltage CMOS device that uses
low-cost external components to control the high
voltages
Figure 15 is a simplified illustration of the linefeed
control loop circuit for TIP or RING and the external
components used.
The ProSLIC uses both voltage and current sensing to
control TIP and RING. DC and AC line voltages on TIP
and RING are measured through sense resistors R
and R
transistors Q
isolates the high-voltage base of Q
The ProSLIC measures voltage at various nodes in
order to monitor the linefeed current. R
R
sense circuitry is calibrated on-chip to guarantee
measurement
component tolerances. See "Linefeed Calibration" on
page 26 for details.
Linefeed Operation States
The ProSLIC linefeed has eight states of operation as
shown in Table 21. The state of operation is controlled
using the Linefeed Control register (direct Register 64).
The open state turns off all currents into the external
bipolar transistors and can be used in the presence of
fault conditions on the line and to generate Open Switch
Intervals (OSIs). TIP and RING are effectively tri-stated
with a dc output impedance of about 150 k . The
ProSLIC can also automatically enter the open state if it
detects excessive power being consumed in the
external bipolar transistors. See "Power Monitoring and
Line Fault Detection" on page 24 for more details.
In the forward active and reverse active states, linefeed
circuitry is on and the audio signal paths are powered
down.
In the forward and reverse on-hook transmission states
audio signal paths are powered up to provide data
transmission during an on-hook loop condition.
The TIP Open state turns off all control currents to the
external bipolar devices connected to TIP and provides
an active linefeed on RING for ground start operation.
The RING Open state provides similar operation with
the RING drivers off and TIP active.
The
waveforms onto the line.
22
BAT
provide access to these measuring points. The
ringing
AC
, respectively. The ProSLIC uses linefeed
required
P
and Q
state
accuracy
for
N
drives
to drive TIP and RING. Q
subscriber
with
programmable
N
standard
from the ProSLIC.
line
DC
, R
interfaces.
Preliminary Rev. 1.11
SE
external
ringing
, and
DC
DN
Loop Voltage and Current Monitoring
The ProSLIC continuously monitors the TIP and RING
voltages and external BJT currents. These values are
available in registers 78–89. Table 22 on page 24 lists
the values that are measured and their associated
registers. An internal A/D converter samples the
measured voltages and currents from the analog sense
circuitry and translates them into the digital domain. The
A/D updates the samples at an 800 Hz rate. Two
derived values are also reported—loop voltage and loop
current. The loop voltage, V
1-bit sign, 6-bit magnitude format. For ground start
operation the reported value is the RING voltage. The
loop current, (I
bit sign, 6-bit magnitude format. In RING open and TIP
open states the loop current is reported as (I
(I
Q5
–I
Q6
).
Q1
– I
Q2
+ I
Q5
TIP
–I
– V
Q6
)/2, is reported in a 1-
RING
, is reported as a
Q1
– I
Q2
) +