EVAL-ADN2805EBZ AD [Analog Devices], EVAL-ADN2805EBZ Datasheet - Page 14

• Manufacturer Part Number: EVAL-ADN2805EBZ
• Description: 1.25 Gbps Clock and Data Recovery IC
• Manufacturer: AD [Analog Devices]

ADN2805
APPLICATIONS INFORMATION
PCB DESIGN GUIDELINES
Proper RF PCB design techniques must be used for optimal
performance.
Power Supply Connections and Ground Planes
Use of one low impedance ground plane is recommended. To
reduce series inductance, solder the VEE pins directly to the
ground plane. If the ground plane is an internal plane and
connections to the ground plane are made through vias, multiple
vias can be used in parallel to reduce the series inductance,
especially on Pin 23, which is the ground return for the output
buffers. Connect the exposed pad to the ground plane using
plugged vias to prevent solder from leaking through the vias
during reflow.
Use of a 22 μF electrolytic capacitor between VCC and VEE is
recommended at the location where the 3.3 V supply enters the
PCB. When using 0.1 μF and 1 nF ceramic chip capacitors,
place them between the IC power supply VCC and VEE, as
close as possible to the ADN2805 VCC pins.
VCC
TRANSCEIVER
0.1µF
OPTICAL
MODULE
+
22µF
0.1µF
1nF
50Ω
50Ω
0.1µF
Figure 14. Typical Applications Circuit
TEST1
VREF
VCC
VCC
VEE
NIN
PIN
NC
NC
1nF
0.1µF
Rev. 0 | Page 14 of 16
1
2
3
4
5
6
7
8
EXPOSED PAD
1nF
TIED OFF TO
VEE PLANE
WITH VIAS
If connections to the supply and ground are made through vias,
the use of multiple vias in parallel helps to reduce series
inductance, especially on Pin 24, which supplies power to the
high speed CLKOUTP/CLKOUTN and DATAOUTP/
DATAOUTN output buffers. Refer to Figure 14 for the
recommended connections.
By using adjacent power supply and ground planes, excellent
high frequency decoupling can be realized by using close
spacing between the planes. This capacitance is given by
where:
ε
A is the area of the overlap of power and ground planes (cm
d is the separation between planes (mm).
For FR-4, ε
50Ω TRANSMISSION LINES
0.47µF ±20%
>300MΩ INSULATION RESISTANCE
r
is the dielectric constant of the PCB material.
C
24
23
22
21
20
19
18
17
µC
PLANE
VCC
VEE
NC
SDA
SCK
SADDR5
VCC
VEE
r
=
= 4.4 mm and 0.25 mm spacing, C ~15 pF/cm
1nF
1nF
. 0
88
ε
0.1µF
I
I
r
0.1µF
2
2
A/d
C CONTROLLER
C CONTROLLER
DATAOUTP
DATAOUTN
CLKOUTP
CLKOUTN
( )
pF
VCC
VCC
2
.
2
).