RFFM4201 Datasheet, PDF (5/14 Pages) RF Micro Devices – 3.3V TO 5V, 2.4GHz TO 2.5GHz HIGH POWER FRONT END MODULE

RFFM4201
Theory of Operation and Applications
The RFFM4201 is a single-chip integrated front end module (FEM) for high performance WiFi applications in the 2.4GHz to
2.5GHz ISM band. The FEM greatly reduces the number of external components minimizing footprint and assembly cost of the
overall 802.11b/g/n solution. The RFFM4201 has an integrated b/g/n power amplifier, a power Detector, and Tx filtering and a
switch, which is capable of switching between WiFi Rx, WiFi Tx operations. The device is manufactured using InGaP HBT and
pHEMT processes on a 6mm x 6mm x 0.95mm laminate package. The module meets or exceeds the RF front end needs of the
802.11b/g/n WiFi RF systems. The RFFM4201 is a very easy part to implement. To reduce the design and optimization pro-
cess on the customer application, the evaluation board layout should be copied as close as possible, in particular the ground
and via configurations. Gerber files of RFMD PCBA designs will be provided upon request. The supply voltage lines should pres-
ent an RF short to the FEM by using bypass capacitors on the V_CC traces. To simplify bias conditions, the RFFM4201 requires a
single positive supply voltage (V_CC), a positive current control bias (V_REG) supply, and a positive supply for switch control. The
built-in power detector of the RFFM4201 can be used as power monitor in the system. All inputs and outputs are internally
matched to 50.
Transmit Path
The RFFM4201 has a typical gain of 34dB form 2.4GHz to 2.5GHz, and delivers 25.5dBm typical output power in 11n HT20
MCS7 and 26dBm typical in 11g 54Mbps. The RFFM4201 requires a single positive of 5.0V to operate at full specifications.
The VREG pin requires a regulated supply at 2.9V to maintain nominal bias current.
Out of Band Rejection
The RFFM4201 contains a low pass filtering (LPF) to attenuate the 2nd Harmonics to -47dBm/MHz (typical), to meet the out of
band rejection requirements of the system for FCC specification.
Receive Path
The Rx path has a 50 single-ended port. The receive port return loss is 9.6dB minimum. In this mode, the FEM has an Inser-
tion loss of 0.8dB and 30dB (typical) isolation to Tx port.
RFFM4201 Biasing Instructions to the Evaluation Board:
• 802.11b/g/n transmit:
• Connect the FEM to a signal generator at the input and a spectrum analyzer at the output. Set the pin at signal generator is
at -20dBm.
• Bias V_CC to 5.0V first with V_REG = 0.0V. If available, enable the current limiting function of the power supply to 750mA.
• Refer to switch operational truth table to set the control lines at the proper levels for WiFi Tx.
• Turn on V_REG to 2.9V (typ.).
On V_REG (of evaluation board), regulated supply is recommended. Be extremely careful not to exceed 3.0V on the VREG pin
or the part may exceed device current limits.
• Turn on P_DOWN to 2.9V (typ.). PDOWN pin can be tied to V_REG supply.
NOTE: It is important to adjust the V_CC voltage source so that +5V is measured at the board; and the +2.9V of V_REG is mea-
sured at the board. The high collector currents will drop the collector voltage significantly if long leads are used. Adjust the
bias voltage to compensate.
• Turn on RF of signal generator and gradually increase power level to the rated power.
CAUTION: If the input signal exceeds the rated power, the RFFM4201 Evaluation Board can be permanently damaged.
• To turn off FEM, turn off RF power of signal generator; then P_DOWN, V_REG and V_CC.
• 802.11b/g/n receive
• To receive WiFi set the switch control lines per the truth table.
DS121008
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at ([phone] or [e-mail].
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