參數(shù)資料
型號(hào): SI3225PPTX-EVB
廠商: Silicon Laboratories Inc
文件頁(yè)數(shù): 41/112頁(yè)
文件大?。?/td> 0K
描述: BOARD EVAL W/DISCRETE INTERFACE
設(shè)計(jì)資源: Si3225PPTX-EVB Schematics/Layout
標(biāo)準(zhǔn)包裝: 1
系列: ProSLIC®
主要目的: 接口,模擬前端(AFE)
已用 IC / 零件: Si3225
已供物品: 板,CD
Si3220/25 Si3200/02
34
Rev. 1.3
Not
Recommended
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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
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.
Table 19. Register and RAM Locations for Linefeed Control
Parameter
Register/
RAM
Mnemonic
Register/RAM
Bits
Programmable
Range
LSB Size
Effective
Resolution
Linefeed
LINEFEED
LF[2:0]
N/A
Linefeed Shadow
LINEFEED
LFS[2:0]
Monitor Only
N/A
Battery Feed Control
RLYCON
BATSEL
VBATH/VBATL
N/A
Loop Current Limit
ILIM
ILIM[4:0]
18–45 mA
0.875 mA
On-Hook Line Voltage
VOC
VOC[14:0]
0 to 63.3 V
4.907 mV
1.005 V
Common Mode Voltage
VCM
VCM[14:0]
0 to 63.3 V
4.907 mV
1.005 V
VOC Delta for Off-Hook
VOCDELTA
VOCDELTA[14:0]
0 to 63.3 V
4.907 mV
1.005 V
VOC Delta Threshold, Low
VOCLTH
VOCLTH[15:0]
0 to 63.3 V
4.907 mV
1.005 V
VOC Delta Threshold, High
VOCHTH
VOCHTH[15:0]
0 to 63.3 V
4.907 mV
1.005 V
Overhead Voltage
VOV
VOV[14:0]
0 to 63.3 V
4.907 mV
1.005 V
Ringing Overhead Voltage
VOVRING
VOVRING[14:0]
0 to 63.3 V
4.907 mV
1.005 V
VOC During Battery Tracking
VOCTRACK
VOCTRACK[15:0]
0 to 63.3 V
4.907 mV
1.005 V
5
512
005
1
2
V
.
voltage
_
desired
ROUND
CEILING
HEX
DEC
RAMValue
Table 20. Adaptive Linefeed Example Values
VBAT
VOV
VCM
VOC
ILIM
VOCLTH
VOCHTH
VOCDELTA
–56 V
4 V
3 V
–48 V
20 mA
–7 V
+2 V
+6 V
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