mrf89xa Microchip Technology Inc., mrf89xa Datasheet - Page 100

• Manufacturer Part Number: mrf89xa
• Description: Ultra-low Power, Integrated Ism Band Sub-ghz Transceiver
• Manufacturer: Microchip Technology Inc.

4.4
The Power Amplifier (PA) integrated in the MRF89XA
operates under a regulated voltage supply of 1.8V. The
external RF choke inductor is biased by an internal reg-
ulator output made available on the PARS pin (pin 29).
These features help PA output power to be consistent
over the power supply range. This is important for
applications that allow predictable RF performance and
battery life.
FIGURE 4-4:
DS70622B-page 100
MRF89XA
Note:
POWER AMPLIFIER
Refer to Section 4.7 “Bill of Materials”
for an optimized PA load setting.
OPTIMAL LOAD IMPEDANCE CHART
Preliminary
4.4.1
As the PA and the LNA front-ends in the MRF89XA
share the same input/output pin, they are internally
matched to approximately 50Ω. Figure 4-4illustrates
optimum load impedance of RFIO through an imped-
ance chart.
Max Power
Zopt = 30 + j25Ω
OPTIMUM LOAD IMPEDANCE
Pmax-1dB circle
© 2010 Microchip Technology Inc.