ADV7127
Power Planes
Supply Decoupling
The PC board layout should have two distinct power planes,
one for analog circuitry and one for digital circuitry. The analog
power plane should encompass the ADV7127 (VAA) and all
associated analog circuitry. This power plane should be con-
nected to the regular PCB power plane (VCC) at a single point
through a ferrite bead, as illustrated in Figure 25. This bead
should be located within three inches of the ADV7127.
Noise on the analog power plane can be further reduced by the
use of multiple decoupling capacitors (see Figure 25).
Optimum performance is achieved by the use of 0.1 µF ceramic
capacitors. Each of the two groups of VAA should be individually
decoupled to ground. This should be done by placing the ca-
pacitors as close as possible to the device with the capacitor
leads as short as possible, thus minimizing lead inductance.
It is important to note that while the ADV7127 contains cir-
cuitry to reject power supply noise, this rejection decreases with
frequency. If a high frequency switching power supply is used,
the designer should pay close attention to reducing power sup-
ply noise. A dc power supply filter (Murata BNX002) will pro-
vide EMI suppression between the switching power supply and
the main PCB. Alternatively, consideration could be given to
using a three terminal voltage regulator.
The PCB power plane should provide power to all digital logic
on the PC board, and the analog power plane should provide
power to all ADV7127 power pins, voltage reference circuitry
and any output amplifiers.
The PCB power and ground planes should not overlay portions
of the analog power plane. Keeping the PCB power and ground
planes from overlaying the analog power plane will contribute to
a reduction in plane-to-plane noise coupling.
COMP
C6
0.1F
ANALOG POWER PLANE
V
AA
ADV7127
C4
0.1F
C5
0.1F
L1 (FERRITE BEAD)
C3
0.1F
+5V (V
)
CC
V
REF
VIDEO
DATA
INPUTS
C2
10F
C1
33F
D0
D9
ANALOG GROUND PLANE
GROUND
GND
L2 (FERRITE BEAD)
R
SET
R1
75⍀
PDOWN
PSAVE
CLOCK
560⍀
R
SET
VIDEO
OUTPUT
I
OUT
COMPONENT
DESCRIPTION
VENDOR PART NUMBER
C1
33F TANTALUM CAPACITOR
10F TANTALUM
C2
C3, C4, C5, C6
L1, L2
0.1F CERAMIC CAPACITOR
FERRITE BEAD
FAIR-RITE 274300111 OR MURATA BL01/02/03
R1
75⍀ 1% METAL FILM RESISTOR DALE CMF-55C
560⍀ 1% METAL FILM RESISTOR DALE CMF-55C
R
SET
Figure 25. Typical Connection Diagram and Component List
–14–
REV. 0
ROCHESTER [ Rochester Electronics ]
