HC5513 datasheet(10/20 Pages) RENESAS

10 / 20 page

HC5513

FN3963 Rev.12.00

Page 10 of 20

August 2003

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

ZTR is defined as:

Substituting in Equation 9 for VTR

Substituting in Equation 12 for VTX

Therefore

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 2.16F.

RF = 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:

(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,

Equation 15) is chosen to equal the line impedance (ZL), the

expression for A4-2 simplifies to:

(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:

VTX

1000

-------------



(EQ. 12)

ZTR

VTR

-----------

(EQ. 13)

ZTR

VTX

-----------

2RF IM



-----------------------

(EQ. 14)

ZTR

1000

-------------

2RF

(EQ. 15)

1000

ZTR 2RF

–





(EQ. 16)

1000

600

 2.16



–



-----------------------------------------

220



–







A24

–

VTX

VTR

-----------

ZT 1000



ZT 1000



2RF

------------------------------------------

(EQ. 17)

A42

–

VTR

VRX

-----------

ZRX

-----------

–

1000

-------------

2RF ZL

--------------------------------------------



(EQ. 18)

A42

–

ZRX

-----------

–

---



(EQ. 19)

A44

–

VTX

VRX

-----------

ZRX

-----------

–

ZL 2RF

1000

-------------

2RF ZL

--------------------------------------------



(EQ. 20)

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