RFFM5765Q Datasheet, PDF (10/15 Pages) RF Micro Devices – Tested in Accordance with AEC-Q100 802.11b/g/n WiFi Front End Module

RFFM5765Q
Theory of Operation
The RFFM5765Q front end module (FEM) is designed for automotive WiFi applications in the 2.5GHz ISM band. It can be
applied in many portable applications such as handsets, portable media players, and portable battery power equipment. This
highly integrated module can be connected directly to the battery without additional voltage regulators.
WiFi Transmit Mode
The RFFM5765Q requires a single positive supply (V_CC), a positive supply for switch controls, and a regulated supply for the
V_REG to maintain nominal bias current. The RFFM5765Q transmit path has a typical gain of 30dB from 2.4GHz to 2.5GHz, and
delivers 19dBm typical output power under 54Mbps OFDM modulation and 22dBm under 1Mbps 11b modulation. The
RFFM5765Q contains basic filter components to produce a bandpass response for the transmit path. Due to space constraints
inside the module, filtering is limited to a few resonant poles and additional filters may be required depending upon the end-
user’s application. While in transmit mode, the active components are the power amplifier (PA) and the Tx branch of the SP3T
switch. Refer to the logic control table for proper settings.
Tx Biasing Instructions
• Connect the Tx input (pin-1) to a signal generator and a spectrum analyzer at the antenna output (pin-10)
• Set V_CC to 3.3V with V_REG set to 0V
• Turn V_REG ON and set voltage to 3.1V. V_REG controls the current drawn by the PA and it should quickly reach a quiescent cur-
rent of approximately 110mA ± 20mA. Care must be exercised not to exceed 3.5V on the V_REG pin or the part may be dam-
aged.
• Control bias to the transmit branch of the SP3T switch is tied directly to V_REG
• The SP3T controls for the off branches (C_RX 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 of the PA will degrade significantly. Likewise,
unused RF ports must be terminated in 50Ω to simulate actual system conditions and prevent RF signals from coupling
back to the PA.
• Turn RF ON
WiFi Receive Mode
Within the frequency band of operation 2.4GHz to 2.5GHz, the RFFM5765Q WiFi receive path has a typical gain of 18dB and a
NF of 2.1dB with about 10mA of current. In Rx mode, only the Rx branch of the SP3T and the LNA are active. Refer to the logic
control table for proper settings.
Rx Biasing Instructions
• Connect the Rx input (ANT/pin-10) to a signal generator and a spectrum analyzer at the Rx output (pin-3). A VNA may be
used as well.
• Turn the LNA bias ON (pin-4) and set the voltage to 3.3V.
• Set C_RX (pin-6) high. This turns ON the receive branch of the SP3T.
• 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.
• Set the control bias for the SPST switch (C_BWRX/pin-5) “low” during WiFi Rx only mode.
• Turn RF ON.
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