參數(shù)資料
型號: HC55142IM
廠商: HARRIS SEMICONDUCTOR
元件分類: 模擬傳輸電路
英文描述: Low Power Universal SLIC Family
中文描述: TELECOM-SLIC, PQCC28
文件頁數(shù): 16/35頁
文件大?。?/td> 382K
代理商: HC55142IM
4-16
The R
OH
resistor, which
is usedtoset the offhook
overhead voltage, is
calculated using
Equations 9 and 10.
I
OH
is defined as the
difference between the
I
LOOP(min)
and ISH-.
Substituting Equation 8
for ISH- into Equation 9 and solving for R
OH
defines R
OH
in
terms of I
LOOP(min)
and R
D
.
OH
Equation 10 can be used to determine the actual ISH- value
resulting from the R
D
resistor selected. The value of R
D
should be the next standard value that is lower than that
calculated. This will insure meeting the I
LOOP(min)
requirement. ROH for the above example equals 39.1k
.
R
500
D
LOOP(min)
The current limit is set by a single resistor and is calculated
using Equation 11.
LOOP(max)
The maximum loop
resistance is calculated
using Equation 12. The
resistance of the
protection resistors
(2R
P
) is subtracted out
to obtain the maximum
loop length to meet the
required off hook
overhead voltage. If R
LOOP(MAX)
meets the loop length
requirements you are done. If the loop length needs to be
longer, then consider adjusting one of the following: 1) the
SHD threshold, 2) minimum loop current requirement or 3)
the on and off hook signal levels.
V
LOOP(min)
SLIC in the Active Mode
Figure 17 shows a simplified AC transmission model. Circuit
analysis yields the following design equations:
Substitute Equation 14 into Equation 15
Substitute Equation 16 into Equation 17
Substitute Equation 18 into Equation 19
Substituting -V
TR
/Z
L
into Equation 20 for I
M
and rearranging
to solve for V
TR
results in Equation 21
where:
V
RX
= The input voltage at the VRX pin.
V
A
= An internal node voltage that is a function of the loop
current detector and the impedance matching networks.
I
X
= Internal current in the SLIC that is the difference
between the input receive current and the feedback current.
I
M
= The AC metallic current.
R
P
= A protection resistor (typical 30
).
Z
T
= An external resistor/network for matching the line
impedance.
V
TX
= The tip to ring voltage at the output pins of the SLIC.
V
TR
= The tip to ring voltage including the voltage across the
protection resistors.
Z
L
= The line impedance.
Z
TR
= The input impedance of the SLIC including the
protection resistors.
(AC) 4-Wire to 2-Wire Gain
The 4-wire to 2-wire gain is equal to V
TR
/V
RX
.
From Equation 21 and the relationship Z
T
= 200(Z
TR
-2R
P
).
V
RX
Notice that the phase of the 4-wire to 2-wire signal is 180
o
out of phase with the input signal.
V
BH
V
SAT
V
OH(off)
2.5V
OFF HOOK
OVER HEAD
T
LOOP CURRENT
I
LOOP(min)
DC FEED CURVE
ISH-
I
OH
R
OH
---------
LOOP(min)
--------------------------------------------
=
=
(EQ. 9)
R
OH
=
-----------------------------------------------------------
(EQ. 10)
R
LIM
=
-----------------------------
(EQ. 11)
V
BH
V
SAT
V
OH(off)
2.5V
T
LOOP CURRENT
I
LOOP(min)
DC FEED CURVE
R
LOOP(MAX)
R
LOOP(max)
=
V
2V
V
)
+
+
[
]
-------------------------------------------------------------------------------
-2R
P
(EQ. 12)
V
A
= I
M
2R
S
---------
200
×
Z
TR
2R
P
(
)
×
5
×
×
(EQ. 13)
V
A
I
M
2
-------
Z
TR
2R
P
(
)
=
(EQ. 14)
V
------------
-
V
------------
= I
X
Node Equation
(EQ. 15)
I
X
V
------------
-
I
Z
-----------------------------------------
2R
(
)
=
(EQ. 16)
I
X
500k - V
TX
+ I
X
500k = 0
Loop Equation
(EQ. 17)
V
TX
2V
RX
I
M
Z
TR
2R
P
(
)
=
(EQ. 18)
V
TR
-I
M
2R
P
+ V
TX
= 0
Loop Equation
(EQ. 19)
V
TR
I
M
Z
TR
2V
RX
=
(EQ. 20)
V
TR
1
Z
L
----------
+
2
V
RX
=
(EQ. 21)
G
4-2
=
----------
= -2
Z
L
TR
-------------------------
2
Z
T
Z
L
---------
2R
P
+
+
----------------------------------------------
=
(EQ. 22)
HC55120, HC55121, HC55130, HC55131, HC55140, HC55141, HC55142, HC55143, HC55150, HC55151
相關PDF資料
PDF描述
HC55143 Low Power Universal SLIC Family
HC55143IM Low Power Universal SLIC Family
HC55150 Low Power Universal SLIC Family
HC55150CB Low Power Universal SLIC Family
HC55150CM Low Power Universal SLIC Family
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