Data Sheet
May 2001
L8576B Dual Ringing SLIC
Transmit gain:
Hybrid balance:
Applications (continued)
ac Design (continued)
VGSX
VT/R
GTX = --------------
RX 125
GTX = ---------- × -----------
RT2 ZT/R
Example 1, Real Termination
The following design equations refer to the circuit in
Figure 20. Use these to synthesize real termination
impedance.
VGSX
hbal = 20log -----------
VT/R
Termination impedance:
VT/R
To optimize the hybrid balance, the sum of the currents
at the VFXIN input of the codec op amp should be set
to 0. The following expressions assume the hybrid bal-
ance network is the same as the termination imped-
ance:
Zt =
----------
–IT/R
1500
Zt = 2RP +
----------------------------------
1 +
RT1
RT1
+
-------- -----------
RGP RRCV
RX
RHB =
--------------------------
Receive gain:
GRCV × GTX
VT/R
GRCV =
-----------
RX
VFRO
hbal = 20log
– GRCV × GTX
--------
RHB
12
GRCV =
------------------------------------------------------------------
RRCV RRCV
Zt
1 +
+
1 +
----------- -----------
--------
ZT/R
RT1
RGP
RX
GSX
TG
1/2 L8576
SLIC
125 V/A
RGX
RT2
VFXIN
–
+
AX
VITR
RT1
RCVN
RHB
–
–
ZT/R
RP
+2.4 V
PT
PR
AV = 6
AV = 1
RRCV
RCVP
VFRO
+
+
IT/R
+
CURRENT
SENSE
VS
ZT
VT/R
–
RGP
+
AV = –1
–
RP
1/2 T8503 CODEC
12-2554.o (F)
Figure 20. ac Equivalent Circuit Using a T8503 Codec
20
Agere Systems Inc.
AGERE [ AGERE SYSTEMS ]
