HC5513 查看數據表（PDF） - Renesas Electronics
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HC5513 Datasheet PDF : 20 Pages
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HC5513
where:
VTR = Is the AC metallic voltage between tip and ring,
including the voltage drop across the fuse resistors RF .
VTX = Is the AC metallic voltage. Either at the ground
referenced 4-wire side or the SLIC tip and ring terminals.
IM = Is the AC metallic current.
RF = Is a fuse resistor.
ZT = Is used to set the SLIC’s 2-wire impedance.
VRX = Is the analog ground referenced receive signal.
ZRX = Is used to set the 4-wire to 2-wire gain.
EG = Is the AC open circuit voltage.
ZL = Is the line impedance.
(AC) 2-Wire Impedance
The AC 2-wire impedance (ZTR) is the impedance looking into
the SLIC, including the fuse resistors, and is calculated as
follows:
Let VRX = 0. Then from Equation 10
VTX
=
ZT
----I--M------
1000
(EQ. 12)
ZTR is defined as:
ZTR
=
V-----T---R---
IM
(EQ. 13)
Substituting in Equation 9 for VTR
ZTR
=
V-----T---X-- + 2----R-----F---------I--M---
IM
IM
Substituting in Equation 12 for VTX
ZTR
=
----Z----T----
1000
+
2RF
Therefore
(EQ. 14)
(EQ. 15)
ZT = 1000 ZTR – 2RF
(EQ. 16)
Equation 16 can now be used to match the SLIC’s impedance
to any known line impedance (ZTR).
Example:
Calculate ZT to make ZTR = 600 in series with 2.16F.
RF = 20:
ZT
=
1000
600
+
-j-----------2----.-1---1-6---------1---0----–--6--
–
2
20
ZT = 560k in series with 2.16nF.
(AC) 2-Wire to 4-Wire Gain
The 2-wire to 4-wire gain is equal to VTX/ VTR.
From Equations 9 and 10 with VRX = 0:
A2 – 4
=
-V----T---X---
VTR
=
-Z---T------Z--1-T--0---0---1-0--0---+0----02----R-----F-
(EQ. 17)
(AC) 4-Wire to 2-Wire Gain
The 4-wire to 2-wire gain is equal to VTR/VRX.
From Equations 9, 10 and 11 with EG = 0:
For applications where the 2-wire impedance (ZTR,
A4 – 2
=
-V----T----R--
VRX
=
–
---Z----T----
ZRX
-------------------Z----L---------------------
----Z----T----
1000
+
2RF
+
ZL
(EQ. 18)
Equation 15) is chosen to equal the line impedance (ZL), the
expression for A4-2 simplifies to:
A4 – 2
=
–---Z----T--- 1--
ZRX 2
(EQ. 19)
(AC) 4-Wire to 4-Wire Gain
The 4-wire to 4-wire gain is equal to VTX/VRX.
From Equations 9, 10 and 11 with EG = 0:
A4 – 4
=
-V----T----X--
VRX
=
–---Z----T----
ZRX
-----------Z---L-----+-----2----R----F------------
----Z----T----
1000
+
2
RF
+
ZL
(EQ. 20)
FN3963 Rev.12.00
August 2003
Page 10 of 20
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