THS6226A_16 Datasheet, PDF (19/32 Pages) Texas Instruments – THS6226A Gated-Class H, Dual-Port VDSL2 Line Driver

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THS6226A
SBOS643A – APRIL 2014 – REVISED MAY 2014
8 Applications and Implementation
8.1 Application Information
The device is a dual-port, very-high-bit-rate digital subscriber line (VDSL), class H line driver. Typically, the signal
is generated by a high-speed digital-to-analog converter (DAC). The device drives a twisted pair.
The digital subscriber line (DSL) system is ac-coupled as it transmits information above the audio band. On the
input of the line driver, this ac-coupling translates into the series capacitors to isolate the dc voltage coming from
the DAC output common-mode voltage. On the output, a transformer is used to help isolate the 48V present
between tip and ring of the telephone line.
The transformer can be set to any useful ratio. In practice, the transformer-turn ratio is set between 1:1 and 1:1.4
for the device. As mentioned in the Feature Description section, the active impedance synthesis factor is 5. This
synthesis factor means that the termination resistor is 1/5th of the load impedance reflected to the transformer
secondary. Thus, the correct termination can be selected based on the transformer-turn ratio.
Note that the resulting load detected by the amplifier may affect the amplifier linearity or output voltage swing
capabilities.
8.2 Typical Application
The typical application circuit for this application is shown in Figure 34.
1mF
VLL_CD
CAPL_CD
V_IN+
IND
+12V
FBC
OUTD
47 W
Device
100kW
+12V
1:n
0.2 × ^RL
33 nF
R_L
2
n
V_IN-
INC
OUTC
FBD
DATA
CLK
47 W
VHH_CD
CAPH_CD
1mF
Figure 34. Typical VDSL Line Driver Circuit Configuration
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