
Sub-GHz radio (SUBGHZ)
RM0453
156/1454
RM0453 Rev 2
5.3.3 Transmitter
The transmit chain comprises the modulated output from the modem, that directly
modulates the RF-PLL. An optional pre-filtering of the bit stream can be enabled to reduce
the power in the adjacent channel also dependent on the selected modulation scheme. The
modulated signal from the RF-PLL directly drives the high-power PA (HP PA) or low-power
PA (LP PA).
Transmitter high output power
Transmit high output power up to + 22 dBm, is supported through the RFO_HP RF pin. The
HP PA can be supplied from the PA regulator (REG PA) up to 3.1 V.
For this, the REG PA must be supplied directly from V
DD
(on VDDSMPS pin), as shown in
the figure below.
Figure 10. High output power PA
HSEBYPPWR
Digital input
Enable VDDTCXO regulator
control
HSERDY
Digital output
HSE32 clock ready indication
SUBGHZSPI
Digital in/output
Sub-GHz radio SPI interface
BUSY
Digital output
BUSY signal
Interrupts
Digital output
IRQ interrupts
Table 26. Sub-GHz internal input/output signals (continued)
Signal name
Signal type
Description
MSv62616V2
VLXSMPS
VFBSMPS (1.55V)
VDDPA
VR_PA (up to 3.1V)
RFO_HP
LDO/SMPS
REG
PA
HP PA
VLXSMPS
VFBSMPS (1.55V)
VDDPA
VR_PA (up to 3.1V)
RFO_HP
LDO/SMPS
REG
PA
HP PA
V
DD
V
DD
V
DD
V
DD
VDDSMPS (1.8 to 3.6V)
VDDSMPS (1.8 to 3.6V)
LDO mode
SMPS mode
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.