ADF7025BCPZ-RL7 Analog Devices Inc, ADF7025BCPZ-RL7 Datasheet - Page 23

• Manufacturer Part Number: ADF7025BCPZ-RL7
• Description: IC,RF Modulator/Demodulator,LLCC,48PIN,PLASTIC
• Manufacturer: Analog Devices Inc

Specifications of ADF7025BCPZ-RL7

• Frequency: 431MHz ~ 464MHz, 862MHz ~ 870MHz and 902MHz ~ 928MHz
• Data Rate - Maximum: 384kbps
• Modulation Or Protocol: FSK
• Applications: Keyless Entery, Home Automation, Wireless Audio/Video
• Power - Output: -20dBm ~ 13dBm
• Sensitivity: -104dBm
• Voltage - Supply: 2.3 V ~ 3.6 V
• Current - Receiving: 19mA
• Current - Transmitting: 28mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 48-LFCSP
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Modulation Type: FSK
• Product Depth (mm): 7mm
• Product Length (mm): 7mm
• Operating Supply Voltage (min): 2.3V
• Operating Supply Voltage (typ): 2.5/3.3V
• Operating Supply Voltage (max): 3.6V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-ADF70XXEKZ1 - KIT DEV ADF702X FOR BF533EZKITEVAL-ADF7025DBZ1 - BOARD EVAL ADF7025 902-928MHZ
• Memory Size: -
• Lead Free Status / Rohs Status: Compliant

APPLICATIONS SECTION
LNA/PA MATCHING
The ADF7025 exhibits optimum performance in terms of
sensitivity, transmit power, and current consumption only if its
RF input and output ports are properly matched to the antenna
impedance. For cost-sensitive applications, the ADF7025 is
equipped with an internal Rx/Tx switch, which facilitates the
use of a simple combined passive PA/LNA matching network.
Alternatively, an external Rx/Tx switch, such as the Analog
Devices ADG919, can be used, which yields a slightly improved
receiver sensitivity and lower transmitter power consumption.
External Rx/Tx Switch
Figure 31 shows a configuration using an external Rx/Tx switch.
This configuration allows an independent optimization of the
matching and filter network in the transmit and receive path,
and is, therefore, more flexible and less difficult to design than
the configuration using the internal Rx/Tx switch. The PA is
biased through Inductor L1, while C1 blocks dc current. Both
elements, L1 and C1, also form the matching network, which
transforms the source impedance into the optimum PA load
impedance, Z
ANTENNA
Rx/Tx – SELECT
Z
power, the frequency range, the supply voltage range, and the
temperature range. Selecting an appropriate Z
minimize the Tx current consumption in the application. This
data sheet contains a number of Z
tive conditions. Under certain conditions, however, it is
recommended to obtain a suitable Z
load-pull measurement.
Due to the differential LNA input, the LNA matching network
must be designed to provide both a single-ended to differential
conversion and a complex conjugate impedance match. The
network with the lowest component count that can satisfy these
requirements is the configuration shown in Figure 31, which
consists of two capacitors and one inductor.
OPT
_PA depends on various factors such as the required output
ADG919
Figure 31. ADF7025 with External Rx/Tx Switch
OPT
_PA.
OPTIONAL
OPTIONAL
(SAW)
LPF
BPF
C
C
B
A
OPT
V
BAT
OPT
Z
Z
Z
_PA values for representa-
L
L1
IN
IN
OPT
A
_RFIN
_RFIN
_PA value by means of a
_PA
PA_OUT
RFIN
RFINB
ADF7025
OPT
_PA helps to
LNA
PA
Rev. A | Page 23 of 44
A first-order implementation of the matching network can be
obtained by understanding the arrangement as two L-type
matching networks in a back-to-back configuration. Due to the
asymmetry of the network with respect to ground, a compro-
mise between the input reflection coefficient and the maximum
differential signal swing at the LNA input must be established.
The use of appropriate CAD software is strongly recommended
for this optimization.
Depending on the antenna configuration, the user might need a
harmonic filter at the PA output to satisfy the spurious emission
requirement of the applicable government regulations. The
harmonic filter can be implemented in various ways, such as a
discrete LC filter or T-stage filter. Dielectric low-pass filter
components such as the LFL18924MTC1A052 (for operation in
the 915 MHz band), or LFL18869MTC2A160 (for operation in
the 868 MHz band), both by Murata Mfg. Co., Ltd., represent an
attractive alternative to discrete designs. The immunity of the
ADF7025 to strong out-of-band interference can be improved
by adding a band-pass filter in the Rx path.
Internal Rx/Tx Switch
Figure 32 shows the ADF7025 in a configuration where the
internal Rx/Tx switch is used with a combined LNA/PA
matching network. This is the configuration used in the
ADF7025DB1 Evaluation Board. For most applications, the
slight performance degradation of 1 dB to 2 dB caused by the
internal Rx/Tx switch is acceptable, allowing the user to take
advantage of the cost-saving potential of this solution. The
design of the combined matching network must compensate for
the reactance presented by the networks in the Tx and the Rx
paths, taking the state of the Rx/Tx switch into consideration.
ANTENNA
BPF OR LPF
OPTIONAL
Figure 32. ADF7025 with Internal Rx/Tx Switch
C
C1
C
A
B
V
BAT
L
L1
Z
Z
Z
A
IN
IN
OPT
_RFIN
_RFIN
_PA
PA_OUT
RFIN
RFINB
ADF7025
ADF7025
LNA
PA