TS613
8/9
By identification of both equations (2) and (3), the
synthesized impedance is, with Rs1=Rs2=Rs:
Unlike the level Vo
°
required for a passive imped-
ance, Vo
°
will be smaller than 2Vo in our case. Let
us write Vo
°
=kVo with k the matching factor vary-
ing between 1 and 2. Assuming that the current
through R3 is negligeable, it comes the following
resistance divider:
RL
After choosing the k factor, Rs will equal to
1/2RL(k-1).
A good impedance matching assumes:
From (4) and (5) it becomes:
By fixing an arbitrary value for R2, (6) gives:
Finally, the values of R2 and R3 allow us to extract
R1 from (1), and it comes:
2
R
3
with GL the required gain.
CAPABILITIES
The table below shows the calculated compo-
nents
for different values of k. In this case
R2=1000
and the gain=16dB. The last column
displays the maximum amplitude level on the line
regarding the TS613 maximum output capabilities
(18Vpp diff.) and a 1:2 line transformer ratio.
MEASUREMENT OF THE POWER
CONSUMPTION IN THE ADSL APPLICATION
Conditions:
Passive impedance matching
Transformer turns ratio: 2
Maximun level required on the line: 12.4Vpp
Maximum output level of the driver: 12.4Vpp
Crest factor: 5.3 (Vp/Vrms)
The TS613 power consumption during emission
on 900 and 4550 meter twisted pair telephone
lines:
360mW
Figure 5 :
Equivalent schematic. Ro is the syn-
thesized impedance
Ro
1
2
R
3
------
–
----------------
4
( )
,
=
Ro
Vi.Gi
Iout
1/2
RL
Ro
2
Rs
1
+
---------------------------
=
Ro
1
2
--
RL
5
( )
,
=
2
R
3
------
1
RL
---------
6
( )
,
–
=
R
3
RL
1
---------
–
-------------------
=
R
1
2 1
------
–
GL
1
–
2
R
3
------
–
---------------------------------------------------------
7
( )
,
=
GL (gain for the
loaded system)
R1
R2 (=R4)
R3 (=R5)
Rs
GL is fixed for the application requirements
GL=Vo/Vi=0.5(1+2R2/R1+R2/R3)/(1-R2/R3)
2R2/[2(1-R2/R3)GL-1-R2/R3]
Abritrary fixed
R2/(1-Rs/0.5RL)
0.5RL(k-1)
Active matching
k
R1
(
)
R3
(
)
Rs
(
)
TS613 Output
Level to get
12.4Vpp on
the line
(Vpp diff)
8
8.7
9.3
9.9
10.5
12.4
Maximum
Line level
(Vpp diff)
1.3
1.4
1.5
1.6
1.7
820
490
360
270
240
1500
1600
2200
2400
3300
3.9
5.1
6.2
7.5
9.1
27.5
25.7
25.3
23.7
22.3
18
Passive matching