SI3220-GQ Silicon Laboratories Inc, SI3220-GQ Datasheet - Page 32

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

Specifications of SI3220-GQ

• 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
• Package / Case: *
• Includes: Battery Switching, BORSCHT Functions, DTMF Generation and Decoding, FSK Tone Generation, Modem and Fax Tone Detection
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Si3220/Si3225
Adaptive Linefeed
The Si3220/Si3225 features a proprietary dc feed
design known as adaptive linefeed.
Figure 16 shows the V/I characteristics of adaptive
linefeed. Essentially, adaptive linefeed changes the
source impedance of the dc feed as well as the
apparent open-circuit voltage (VOC) in order to ensure
the ability to source extended loop lengths. The
following sections provide a detailed explanation of
adaptive linefeed.
Adaptive Linefeed Example
This section provides a detailed description of adaptive
linefeed operation by utilizing an example. The behavior
of adaptive linefeed is controlled by the following RAM
locations: VOV, VCM, VOC, VOCLTH, VOCHTH and
VOCDELTA (see Equation 1). The ILIM register also
plays a role in determining the behavior of the dc feed
as it sets the current limit for the constant current
32
Parameter
Linefeed
Linefeed Shadow
Battery Feed Control
Loop Current Limit
On-Hook Line Voltage
Common Mode Voltage
V
V
V
Overhead Voltage
Ringing Overhead Voltage
V
OC
OC
OC
OC
VBAT
–56 V
Delta for Off-Hook
Delta Threshold, Low
Delta Threshold, High
During Battery Tracking
VOV
4 V
Table 18. Register and RAM Locations for Linefeed Control
Table 19. Adaptive Linefeed Example Values
VCM
VOCTRACK
VOCDELTA
3 V
Mnemonic
LINEFEED
LINEFEED
VOVRING
Register/
VOCHTH
RLYCON
VOCLTH
RAM
VCM
VOC
VOV
ILIM
–48 V
VOC
VOCTRACK[15:0]
VOCDELTA[14:0]
VOVRING[14:0]
VOCHTH[15:0]
Register/RAM
VOCLTH[15:0]
Rev. 1.0
VOC[14:0]
VCM[14:0]
VOV[14:0]
LFS[2:0]
ILIM[4:0]
BATSEL
LF[2:0]
Bits
source. ILIM is a 5-bit register field, which is
programmable from 18 mA to 45 mA in 0.875 mA steps
(i.e., ILIM = 0x0 corresponds to 18 mA and ILIM= 0x1F
corresponds to 45 mA).
The following equation is used to calculate VOV, VCM,
VOC, VOCLTH, VOCHTH and VOCDELTA.
In the above equation, the ROUND function rounds the
result to the nearest integer while the CEILING function
rounds-up the result to the nearest integer. The
DEC2HEX function converts a decimal integer into a
hexadecimal integer.
The RAM values shown in Table 19 where used to
generate the adaptive linefeed V/I curve shown in
Figure 16. Note that a battery voltage of –56 V was
assumed, as shown in Table 19.
RAMValue
20 mA
ILIM
=
DEC
VBATH/VBATL
Programmabl
See Table 17
Monitor Only
2
0 to 63.3 V
0 to 63.3 V
0 to 63.3 V
0 to 63.3 V
0 to 63.3 V
0 to 63.3 V
0 to 63.3 V
0 to 63.3 V
HEX
18–45 mA
VOCLTH
e Range
–7 V




2
⋅
CEILING

 

ROUND
VOCHTH
LSB Size
0.875 mA
4.907 mV
4.907 mV
4.907 mV
4.907 mV
4.907 mV
4.907 mV
4.907 mV
4.907 mV
+2 V
N/A
N/A
N/A



desired
1
.
005
_
VOCDELTA
voltage
Resolutio
V
0.875 mA
Effective
1.005 V
1.005 V
1.005 V
1.005 V
1.005 V
1.005 V
1.005 V
1.005 V
+6 V
N/A
N/A
N/A
n

⋅ 

512
5

 




