MRF49XA-I/ST Microchip Technology, MRF49XA-I/ST Datasheet - Page 74

• Manufacturer Part Number: MRF49XA-I/ST
• Description: IC RF TXRX 433/868/915 16-TSSOP
• Manufacturer: Microchip Technology

Specifications of MRF49XA-I/ST

• Package / Case: 16-TSSOP
• Frequency: 433MHz, 868MHz, 915MHz
• Data Rate - Maximum: 256kbps
• Modulation Or Protocol: FHSS, FSK
• Applications: Home / Industrial Automation, Remote Access, Security Alarms
• Power - Output: 7dbm
• Sensitivity: -110dBm
• Voltage - Supply: 2.2 V ~ 3.8 V
• Current - Receiving: 11mA
• Current - Transmitting: 15mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Number Of Receivers: 1
• Number Of Transmitters: 2
• Wireless Frequency: 433 MHz to 915 MHz
• Output Power: + 7 dBm
• Operating Supply Voltage: 2.5 V, 3.3 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Modulation: FHSS, FSK
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Memory Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 579-MRF49XA-1/ST

4.2
The MRF49XA is designed to drive a differential output,
such as a dipole antenna or a loop antenna. The loop
antenna is ideally suited for applications where com-
pact size is required. The dipole is typically not a good
option for compact designs due to its inherent size at
resonance, and its space requirements around the
ground plane, to be an efficient antenna. A monopole
antenna can be used, along with a balun, or by using
the matching circuit.
TABLE 4-1:
4.4
The guidelines in this section help the users in
high-frequency PCB layout design.
The printed circuit board is usually comprised of two or
four basic FR4 layers.
The two-layer printed circuit board has mixed
signal/power/RF and common ground routed in both
the layers.
FIGURE 4-3:
FIGURE 4-4:
DS70590B-page 72
MRF49XA
Antenna Design Considerations
General PCB Layout Design
MRF49XA
433 MHz
868 MHz
915 MHz
FREQUENCY BAND – ANTENNA ADMITTANCE/IMPEDANCE
TWO BASIC COPPER FR4 LAYERS
FOUR BASIC COPPER FR4 LAYERS
Admittance (ms)
1.49-j12.8
1.2-j11.9
2-j5.9
Preliminary
4.3
The RF pins are of high impedance and differential
value. The optimum differential load for the RF port at
a given frequency band is shown in Table 4-1.
These load values in the table are expected by the RF
port pins to have as an antenna load for maximum
power transfer. Antennas that are suited for such
values would be a Loop, Dipole and Folded Dipole. For
all antenna applications, either a bias, choke inductor
or coils must be included during transmission since the
RF outputs are of open-collector type.
The four-layer printed circuit board is comprised of the
following layers:
• Signal layout
• RF ground
• Power line routing
• Common ground
The four-layer PCB is shown in Figure 4-4.
Impedance (Ω)
52 + j152
7.8 + j83
9 + j77
RF Transmitter Matching
Dielectric Constant = 4.5
Signal Layout
Ground
Signal/Power/RF and
Signal/Power/RF and
Dielectric Constant = 4.5
RF Ground
Dielectric Constant = 4.5
Power Line Routing
Dielectric Constant = 4.5
Common Ground
Common Ground
© 2009 Microchip Technology Inc.
Inductance (nH)
15.4
13.6
62