EVAL-ADF7901EB Analog Devices Inc, EVAL-ADF7901EB Datasheet - Page 10

• Manufacturer Part Number: EVAL-ADF7901EB
• Description: BOARD EVALUATION FOR ADF7901
• Manufacturer: Analog Devices Inc
• Type: Transmitter, UHFr

Specifications of EVAL-ADF7901EB

• Frequency: 369.5MHz ~ 395.9MHz
• For Use With/related Products: ADF7901
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

ADF7901
LAYOUT GUIDELINES
The layout of the board is crucial to ensuring low levels of
spurious and harmonics.
Decoupling
Decoupling capacitors (high frequency 22 pF, low frequency
100 nF) should be placed as close as possible to the supply pins
on the part. Low size 0402 and 0603 components are recom-
mended for the high frequency rejection on the supply.
Regulator Stability
A minimum of 1 μF is needed on both C
stability. An additional 22 pF capacitor can be added to reject
higher frequency noise. Because many of the internal blocks
run off the regulator, it is critical to reduce its noise. Low size
0402 and 0603 components are recommended for the high
frequency rejection on the supply.
VCO IN
3.6kΩ
Figure 8. Applications Diagram for the ADF7901 in a Remote Control System
C
PA_EN
VCO
R
CP
TxDATA
FSK1
FSK2
FSK3
OOK_SEL
22nF
SET
CE
OUT
REG1
C
REG2
and C
2.2μF
ADF7901
C
REG1
REG2
2.2μF
to ensure
RSET_OOK
RSET_FSK
Rev. A | Page 10 of 12
RF
VCO
OSC2
OSC1
GND
DV
OUT
IN
DD
NOTES
1. DECOUPLING CAPACITORS HAVE
BEEN OMITTED FOR CLARITY.
9.8304MHz
27nH
MATCHING RF
3.6kΩ
Grounding
Emphasis should be placed on grounding once the decoupling
capacitors have been added. The PA stage switches currents of
15 mA in maximum power mode. This causes changes in the
ground resulting in large return currents that can radiate to
other parts of the board. The shortest and least obstructed
ground from RF
ensured. A 4-layer board helps, as well as flooding the top layer.
The ground paths should not have any vias and should be wide
tracks.
Supply
The supply tracks can be routed through vias, because they act
as free inductors and make layout easier on a 2-layer board
(see the Decoupling section). Tracks should be wide.
Digital Lines
Digital lines should contain a large resistor in series. This
impedance blocks signals of many frequencies, including
harmonics and the carrier frequency. Long control lines can
act as antennae. It can be useful to add capacitance to ground.
There is some capacitance to ground provided by the lines and
at the input of the digital pins.
33pF
3.6kΩ
5.6pF
33pF
5TH-ORDER, LOW-PASS FILTER
3pF
OUT
22nH
TO 50Ω
GND
8pF
22nH
back to the ground of the battery should be
3pF
MATCHING 50Ω
TO ANTENNA
1.5pF
36nH
ANTENNA