HC55130IMZ datasheet(18/36 Pages) RENESAS

18 / 36 page

HC55120, HC55121, HC55130, HC55140, HC55142, HC55143, HC55150

FN4659 Rev 13.00

Page 18 of 36

June 1, 2006

VTR = The tip to ring voltage including the voltage across the

protection resistors.

ZL = The line impedance.

ZTR = 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 VTR/VRX.

From Equation 21 and the relationship ZT = 200(ZTR-2RP).

Notice that the phase of the 4-wire to 2-wire signal is 180°out

of phase with the input signal.

(AC) 2-Wire to 4-Wire Gain

The 2-wire to 4-wire gain is equal to VTX/EG with VRX = 0

From Equation 18 with VRX = 0

Substituting Equation 24 into Equation 23 and simplifying.

By design, VTX = -VTX´, therefore

A more useful form of the equation is rewritten in terms of

VTX/VTR. A voltage divider equation is written to convert

from EG to VTR as shown in Equation 27.

Rearranging Equation 27 in terms of EG, and substituting

into Equation 26 results in an equation for 2-wire to 4-wire

gain, that’s a function of the synthesized input impedance of

the SLIC (ZTR) and the protection resistors (RP).

Notice that the phase of the 2-wire to 4-wire signal is in

phase with the input signal.

(AC) 4-Wire to 4-Wire Gain

The 4-wire to 4-wire gain is equal to VTX/VRX, EG = 0.

From Equation 18.

Substituting -VTR/ZL into Equation 29 for IM results in

Equation 30.

G4-2 =

VTR

VRX

----------- = -2

ZL + ZTR

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

200

---------- 2RP





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

–

(EQ. 22)

VTX

VRX

TIP

RING

ZTR

VTR

VTX´

VTX

UniSLIC14

VRX

FIGURE 17. SIMPLIFIED AC TRANSMISSION CIRCUIT

500K

PTG

VA = IM(ZTR-2RP)



1/80K

= 200 (ZTR - 2RP)

A = 1

RINT



RINT



– G ZLIM 2RPIM VTX

–

Loop Equation

(EQ. 23)

VTX

IM ZTR 2RP

–



–

(EQ. 24)

IM ZL ZTR



(EQ. 25)

G2-4 =

VTX

---------- =

IM ZTR 2RP

–



IM ZL ZTR



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

ZTR 2RP

–



ZL ZTR



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

(EQ. 26)

VTR =

ZTR

ZTR ZL

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







(EQ. 27)

G2-4 =

VTX

VTR

----------- =

ZTR - 2RP

ZTR

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

(EQ. 28)

VTX

– TX

– VRX IM ZTR 2RP

–



(EQ. 29)

VTX

– VRX

VTR ZTR 2RP

–



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

–

(EQ. 30)

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