Datasheet

2.0
-1.0
Frequency(MHz)
1694FCableAttenuation(dB)
EqualizerGain(dB)
1 100
1.5
1.0
10
-0.5
0
0.5
CableAttenuations
VCA820with
Equalization
9
6
-24
Frequency(Hz)
Gain(dB)
1M 1G
3
-21
-3
0
100M10M
-18
-15
-12
-9
-6
InitialFrequencyResponse
ofVCA820withRCLoad
EqualizedFrequency
Response
R
2
1.33kW
+V
IN
R
G+
R
G-
-V
IN
R
9
1.27kW
C
9
10 Fm
R
8
50W
R
5
50W
R
1
20W
V
IN
R
10
75W
VCA820
R
21
8.7kW
C
5
1.42pF
R
17
17.5kW
C
6
120nF
R
18
40kW
C7
100nF
V
OUT
V
G DC
=+2V
75 LoadW
V
G
GND
V
REF
FB
V
OUT
VCA820
www.ti.com ............................................................................................................................................ SBOS395C –OCTOBER 2007–REVISED OCTOBER 2009
Figure 81. Cable Attenuation versus Equalizer
Figure 80. Differential Equalization of an RC Load
Gain
DIFFERENTIAL CABLE EQUALIZER
Note that this implementation shows the cable
attenuation side-by-side with the equalization in the
A differential cable equalizer can easily be
same plot. For a given frequency, the equalization
implemented using the VCA820. An example of a
function realized with the VCA820 matches the cable
cable equalization for 100 feet of Belden Cable
attenuation. The circuit in Figure 82 is a driver circuit.
1694F is illustrated in Figure 82, with the result for
To implement a receiver circuit, the signal is received
this implementation shown in Figure 81. This
differentially between the +V
IN
and –V
IN
inputs.
implementation has a maximum error of 0.2dB from
dc to 40MHz.
Figure 82. Differential Cable Equalizer
Copyright © 2007–2009, Texas Instruments Incorporated Submit Documentation Feedback 21
Product Folder Link(s): VCA820