Datasheet
Data Sheet AD8335
Rev. B | Page 21 of 28
BASIC CONNECTIONS
Figure 58 shows the basic connections for the AD8335. Input
signals enter from the left and output signals exit from the right,
providing straight line signal paths. Of course, a device with
four differential VGAs such as this requires a multilayer printed
circuit board. Power supply isolation is shown for the preamps,
and for the VGA sections. If components are mounted to both
sides of the board, those in the signal path should be located on
the top, with power-supply decoupling components on the
wiring side.
PREAMP CONNECTIONS
To configure the AD8335 for input matching, a feedback resistor
(R
FB
) is ac-coupled between Pin PONx and Pin PIPx. AC coupling
accommodates dissimilar common-mode voltages at the input
and output ports. For values of R
SOURCE
between 50 Ω and 200 Ω,
R
FB
is simply 5 × R
SOURCE
. Table 6 lists a few larger values of source
resistor (or R
IN
), along with the exact value and nearest standard
1% feedback resistor. For values other those than listed in Table 6,
R
FB
can be calculated using Equation 6. For values larger than
1 kΩ, it may be advantageous to simply remove R
FB
.
Table 6. Feedback Resistor Values for Various Input
Resistances
R
IN
(Ω) Exact R
FB
Value (Ω) Nearest Standard 1% Value (Ω)
200 1014 1.02 k
500 2588 2.61 k
1000 5365 5.36 k
k7.14
1
5
)(
IN
IN
FB
R
R
R
−
×
=
(6)
PIP2
C
SH
2
22pF
R
FB
2
249Ω
PIP3
C
SH
3
22pF
R
FB
3
249Ω
R
SH
3
49.9Ω
R
SH
4
49.9Ω
C
SH
4
22pF
R
FB
4
249Ω
120nH FB
+5V
VOH3
VOH4
R
SH
1
49.9Ω
C
SH
1
22pF
R
FB
1
249Ω
VGN2
1nF*
SL12
120nH FB
+5V
1nF*
1nF*
SL34
VGN1
H
+5V
L
PIP4
+5V
PIP1
VPP
VPP
+5V
VOH1
VOL1
VOL2
VOH2
VOL3
VPV
VPV
VOL4
VGN3VGN4
VPP
VPP
1nF*
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1
µ
F
0.1µF
50
49
56 55 5154 53 5258
57
5962 61 60
VIP1
PON1
VCM2
PIP1
63
POP1
VPP1
VIN1
EN12
VCM1
PMD1
VGN1
SL12
VGN2
SP12
COM1
64
HL12
GND4
VPV2
VOL2
VOH1
VOL1
VOH2
VPV4
VOH3
VOL3
VOH4
VPV3
VOL4
VPV1
GND1
35
36
37
38
42
39
40
41
34
33
48
47
43
46
45
44
GND3
GND2
H
+5V
L
2825 26 2717 18 19 21 22
23
24 29
30
31 32
PMD4
PIP4
POP4
VPP4
SP34
SL34
EN34
VCM3
VIP4
VCM4
COM4
VGN4
VIN4
VGN3
PON4
HL34
20
PMD2
PON2
PIP2
COM2
VIP2
VIN2
POP2
COM3
VIP3
VIN3
PIP3
PON3
PMD3
POP3
VPP3
VPP2
15
16
8
7
6
5
1
4
3
2
14
13
9
12
11
10
AD8335
04976-056
VPP
*SEE TEXT
R
SH
2
49.9Ω
Figure 58. Basic Connections for R
IN
= 50 Ω