Semtech LR1121 - Power Amplifiers; Figure 9-1: LR1121 Power Amplifiers

LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
84 of 130
Semtech
Proprietary & Confidential
www.semtech.com
9. Power Amplifiers
The LR1121 features 2 power amplifiers for sub-GHz operation, and one power amplifier for HF (2.4GHz) operation:
• A high power PA (HP PA), optimized for +22dBm operation
• A low power PA (LP PA), optimized for +14dBm operation, capable of +15dBm output power
• A high frequency PA (HF PA), optimized for +13dBm operation in the 2.4GHz band
Figure 9-1: LR1121 Power Amplifiers
The PA is configured using two commands: SetPaConfig(...) and SetTxParams(...).
The SetPaConfig(...) command is used to:
• Select the PA to be used (HP, LP or HF)
• Select the supply of the PA (VBAT or VREG)
• Select the duty cycle of either PA
• Select the size of the PA (only applicable to the high power PA).
The SetTxParams(...) command is used to:
• Control the supply voltage of the PA (VR_PA) and output power
• Choose the ramp time at the start / stop of TX
The user should configure the PA corresponding to the output power and current consumption requirements of the
application. No automatic frequency limitation is performed during the PA selection: the frequency selection has to be
performed according to the capability offered by the external matching network component values.
LNA
LF0
PA
HP LF
PA
LP LF
RFO_HP_LF
RFO_LP_LF
RFI_P_LF0
RFI_N_LF0
PA
HF
LNA
HF
Balun
&
Match
RFIO_HF
ADCADC
PLL
VBAT_RF
VR_PA
VREG
DCC_SW
VBAT_DCC
VBAT_RF
DC-DC
LDO
BG/IREF
POR/
BRN
PDS
REGsREGs
HFXOSC
32MHz
CKS
LFXOSC
32kHz
HFRC
32MHz
LFRC
32kHz
XTA
XTB
DIO11/ 32k_P
DIO10/32k_N
VTCXO
DIO0/ BUSY
DIO1
DIO2
DIO3
DIO4
DIO9
DIO8
DIO7
DIO6
DIO5
REG_PA
Digital Baseband
+ DSP
CPU
RAMROM
NVM
IO Control
Digital Front-End
LoRa
modem
(G)FSK
modem
LoRa
modem
(G)FSK
modem
nRESET
150 - 960MHz, RX/TX
1.9 - 2.6GHz, RX/TX