SI3202-G-GSR Silicon Laboratories Inc, SI3202-G-GSR Datasheet - Page 34

• Manufacturer Part Number: SI3202-G-GSR
• Manufacturer: Silicon Laboratories Inc

Specifications of SI3202-G-GSR

• Lead Free Status / RoHS Status: Compliant

Si3220/25 Si3200/02
3.4. 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.
3.4.1. 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
34
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 19. Register and RAM Locations for Linefeed Control
Table 20. Adaptive Linefeed Example Values
VOCTRACK
VOCDELTA
VCM
Mnemonic
LINEFEED
LINEFEED
VOVRING
3 V
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]
VOC[14:0]
VCM[14:0]
VOV[14:0]
ILIM[4:0]
LFS[2:0]
BATSEL
Rev. 1.3
LF[2:0]
Bits
source. ILIM is a 5-bit register field, which is
programmable from 18 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 20 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 20.
RAMValue
20 mA
ILIM
=
DEC
Programmable
See Table 18
Monitor Only
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
0 to 63.3 V
18–45 mA
2
BATH
HEX
Range
VOCLTH
–7 V
⎛
⎜
⎜
⎝
/V
2
⋅
BATL
CEILING
⎛
⎜ ⎜
⎝
ROUND
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
VOCHTH
4.907 mV
+2 V
N/A
N/A
N/A
⎛
⎜
⎝
desired
1
.
005
_
Resolution
VOCDELTA
voltage
0.875 mA
Effective
V
1.005 V
1.005 V
1.005 V
1.005 V
1.005 V
1.005 V
1.005 V
1.005 V
N/A
N/A
N/A
+6 V
⎞
⋅ ⎟
⎠
512
5
⎞
⎟ ⎟
⎠
⎞
⎟
⎟
⎠