
RM0453 Rev 2
157/1454
RM0453
Sub-GHz radio (SUBGHZ)
217
The table below gives the maximum transmit output power versus the V
DDPA
supply level.
Transmitter low output power
The transmit low output power up to + 15 dBm, is supported through the RFO_LP pin. The
LP PA can be supplied from the PA regulator (REG PA) up to 1.35 V. For this, the REG PA
must be supplied from the regulated V
FBSMPS
supply at 1.55 V, as shown in the figure
below.
The output power range is programmable in 32 steps of ~1 dB. The power amplifier ramping
timing is also programmable.This allows adaptation to meet radio regulation requirements.
Figure 11. Low output power PA
5.3.4 Receiver
The receive chain comprises a differential low-noise amplifier (LNA), a down-converter to
low-IF by mixer operation in quadrature configuration. The I and Q signals are low pass
filtered and a
Ʃ∆
ADC converts them into the digital domain. In the digital modem, the
signals are decimated, further down converted and channel filtered. The demodulation is
done according to the selected modulation scheme.
The down mixing to low-IF is done by mixing the receive signal with the local RF-PLL
located in the negative frequency, where -f
lo
= -f
rf
+ -f
if
. (where f
lo
is the local RF-PLL
frequency, f
rf
is the received signal and f
if
is the intermediate frequency). The wanted signal
is located at f
rf
= f
lo
+ f
if
.
Table 27. Sub-GHz radio transmit high output power
V
DDPA
supply (V)
Transmit output power (dBm)
3.3
+ 22
2.7
+ 20
2.0
+ 16
MSv62617V2
Note: Use of the SMPS is optional. When SMPS is not used, the BOM can be reduced by removing the coil
between VLXSMPS and VFBSMPS pins.
VLXSMPS
VFBSMPS (1.55V)
VDDPA
VR_PA (up to 1.35V)
RFO_LP
LDO/SMPS
REG
PA
LP PA
LDO mode
SMPS mode
VDDSMPS (1.8 to 3.6V)
V
DD
VLXSMPS
VFBSMPS (1.55V)
VDDPA
VR_PA (up to 1.35V)
RFO_LP
LDO/SMPS
REG
PA
V
DD
LP PA
VDDSMPS (1.8 to 3.6V)