SI3201-X-FS SILABS [Silicon Laboratories], SI3201-X-FS Datasheet - Page 19

• Manufacturer Part Number: SI3201-X-FS
• Manufacturer: SILABS [Silicon Laboratories]

2.2.2. Linefeed Architecture
The Si3233 uses either the Si3201 linefeed interface IC
or a low-cost external circuit to generate the high
voltages required for subscriber line interfaces.
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 R1/R3
and R8/R9, respectively.
The ProSLIC measures voltage at various nodes in
order to monitor the linefeed current. The sense circuitry
is calibrated on-chip to guarantee measurement
accuracy with standard external component tolerances.
See "2.2.9. Linefeed Calibration" on page 23 for details.
2.2.3. Linefeed Operation States
The ProSLIC linefeed has eight states of operation as
shown in Table 20. 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
*Note: The ProSLIC uses registers that are both directly
Parameter
V
V
I
LIM
OC
CM
Table 19. Programmable Ranges of DC
and indirectly mapped. A “direct” register is one that
is mapped directly.
Programmable
20 to 41 mA
Linefeed Characteristics
0 to 94.5 V
0 to 94.5 V
Range
Default
20 mA
Value
48 V
3 V
VCM[5:0]
Register
VOC[5:0]
ILIM[2:0]
Bits
Register 71
Register 72
Register 73
Location*
Preliminary Rev. 0.5
Direct
Direct
Direct
Intervals (OSIs). TIP and RING are effectively tri-stated
with a dc output impedance of about 150 kΩ. The
ProSLIC can also automatically enter the open state if it
detects excessive power being consumed in the
external
Monitoring and Line Fault Detection" on page 21 for
more details.
In the forward active and reverse active states, linefeed
circuitry is on and the audio signal paths are powered
down during an on-hook loop condition.
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
line driver 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.
2.2.4. 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 21 on page 20 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
ringing
).
bipolar
Q1
state
– I
transistors.
Q2
drives
+ I
Q5
TIP
–I
– V
Q6
programmable
See
)/2, is reported in a 1-
RING
, is reported as a
"2.2.5.
Si3233
Q1
– I
ringing
Power
Q2
) +
19