RFFM5765Q Datasheet, PDF (11/15 Pages) RF Micro Devices – Tested in Accordance with AEC-Q100 802.11b/g/n WiFi Front End Module

RFFM5765Q
WiFi and Bluetooth Receive (Simultaneous Mode)
The RFFM5765Q WiFi and Bluetooth receive circuits were specifically designed to address issues of simultaneous operation.
In this mode both signals can be received at the same time when the C_BWRX (pin-5) is set high. The typical gain for each RF
path is approximately 13dB and a NF of 3dB. During simultaneous mode the active components are the LNA, the SPST switch,
and only the Rx branch of the SP3T. Refer to the logic control table for proper settings.
Simultaneous Mode Biasing Instructions
• Connect the RF input (ANT/pin-10) to a signal generator and a spectrum analyzer at the Rx (pin-3) and BT (pin-8) RF ports. A multiport VNA
may be used as well.
• Turn the LNA bias ON (pin-4) and set the voltage to 3.3V.
• Set C_RX and C_BWRX high. This turns ON the receive branch of the SP3T and the SPST switch.
• The SP3T controls for the off branches (V_REG and C_BT) must be set to a logic “low” (0.2V max) or grounded. In the event that one of these
branches is left floating or in a logic “high” the performance will degrade. It is recommended to terminate unused RF Ports in 50Ω.
• Turn RF ON.
Bluetooth Mode
The RFFM5765Q Bluetooth only mode is implemented through the SP3T switch by setting C_BT “high.” Typical insertion loss is
about 1.2dB.
Bluetooth Biasing Instructions
• Connect the RF input (ANT/pin-10) to a signal generator and a spectrum analyzer at the BT RF port. A VNA may be used in place of the Sig
Gen and SA.
• Set C_BT (pin-9) “high.” This turns the Bluetooth branch of the SP3T switch ON.
• The SP3T controls for the off branches (V_REG and C_RX) must be set to a logic “low” (0.2V max) or grounded. Do not leave floating.
• Terminate unused RF Ports in 50Ω.
• Turn RF ON.
Application Circuit and Layout Recommendations
The RFFM5765Q integrates the matching networks and DC blocking capacitors for all RF ports. This greatly reduces the num-
ber of external components and layout area needed to implement this FEM. Typically only a total of four external components
are required to achieve nominal performance. However, depending on board layout and the many noise signals that could
potentially couple to the RFFM5765Q, additional bypassing capacitors may be required to properly filter out unwanted signals
that might degrade performance.
The LNA bias components consist of an inductor and a decoupling capacitor. The inductor value is critical to optimize NF and
return loss at the Rx output. For best performance and trade off between critical parameters such as NF, Gain, and IP3, the
total inductance including board trace should be approximately 1.2nH. The 5.6kΩ series resistor for the Bluetooth control line
helps to prevent unwanted signal from coupling to this pin. The resistor should be place as close as possible to the package
pin. The last component needed in the application circuit is a low frequency bypass capacitor on the V_CC line. In general, it is
good RF practice to have proper decoupling of supply lines to filter out noise. Occasionally, depending on the level of coupling
or parasitics of the board, a high frequency bypass capacitor must be added as well.
In order to optimize performance for both the transmit and receive paths, a good layout design must be implemented. In addi-
tion to designing 50 RF lines, proper grounding along the RF traces and on the FEM ground slug must be exercised. This will
minimize coupling and provide good thermal dissipation when the PA is operating at high power. For reference, the RFMD eval-
uation board uses 9 thermal ground vias (hole/capture pad 12/22mil) on the ground slug. Additionally, if space permitted, V_CC
and control lines must be isolated from each other with ground vias in between them. RFMD evaluation board gerbers are
available upon request.
DS121126
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at ([phone] or [e-mail].
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