Single-Chip Low Power RF Transceiver for Narrowband Systems ...

LNA_EN and PA_EN are used to control the external T/R switch.
22.2. General Purpose Output Control Pins
CC1021
The two digi tal output pins, PA_EN
and is controlled by LOCK_SELECT[3:0]
in the
LN A_EN, can be used as two
general LOCK
register. The LOCK pin is low when
control signals by setting EXT_PA = 0 and LOCK_SELECT[3:0]
= 0000, and high
EXT_LNA = 0. The output value
is then when
LOCK_SELECT[3:0] = 0001.
set directly by the value written to
EXT_PA_POL and EXT_LNA_POL. These
features can be used to save I/O
pins
on the microcontroller when the other
The LO CK pin can also be used as a functions
associated with these pins are
general- purpose output pin. The
LOCK pin not used.
22.3. PA_EN and LNA_EN Pin Drive
Figure 35 shows the PA_EN and
LNA_EN currents
have opposite
signs but absolute
pin drive current s. The sink and source values
are used in Figure 35.
Current [uA]
1400
1200
1000
800
600
400
200
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
Voltage on PA_EN/LNA_EN pin [V]
source current, 3 V sink current, 3V source current, 2.3 V
sink current, 2.3 V source current, 3.6 V sink current, 3.6 V
2.6
Figure
35. PA_EN and LNA_EN pin drive
23. System Considerations and Guidelines
SRD regulations International regulations and
national
laws
regulate
the use of radio receivers
and
transmitters.
SRDs (Short Range Devices)
for license free operation are allowed to
operate in the 433 and 868 - 870 MHz
bands in most European countries. In the
United States, such devices operate in the
2.8
3
3.2
3.4
3.6
260 – 470 and 902 - 928 MHz bands. A
summary
of the most
important aspects of
these
regulations can be found in
Application Note AN001 SRD regulations
for license free transceiver operation,
available from the Chipcon web site.
SWRS045B Page 61 of 89