MRF89XAM8A-I Datasheet, PDF (97/140 Pages) Microchip Technology – Ultra Low-Power, Integrated ISM Band Sub-GHz Transceiver

MRF89XA
4.4.2
SUGGESTED PA BIASING AND
MATCHING
The recommended PA bias and matching circuit is
illustrated in Figure 4-5.
FIGURE 4-5:
RECOMMENDED PA BIASING AND OUTPUT MATCHING
PARS
100 nH
0.047 µF
1W 1%
PA
RFIO
SAW
Antenna
port
DC block
Low-pass and DC block
Refer to Section 4.7, Bill of Materials for the optimized
matching arrangement for each frequency band.
4.4.3
COMMON INPUT AND OUTPUT
FRONT-END
The Receiver and Transmitter share the same RFIO
pin (pin 31). Figure 4-6 illustrates the configuration of
the common RF front-end.
In Transmit mode, the PA and PA regulator are active,
with the voltage on the PARS pin equal to the nominal
voltage of the regulator (1.8V). The external inductance
is used to bias the PA.
In Receive mode, both the PA and PA regulator are
OFF and PARS is tied to ground. The RF choke induc-
tor is then used to bias the LNA.
FIGURE 4-6:
PARS
To
RFIO
Antenna
FRONT-END
DESCRIPTION
PA
Regulator
(1.8V)
RX ON
PA
LNA
© 2010–2011 Microchip Technology Inc.
Preliminary
DS70622C-page 97