Semtech LR1121 - Low Power PA; Figure 9-3: Low Power PA VR_PA Voltage Vs

LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
86 of 130
Semtech
Proprietary & Confidential
www.semtech.com
9.1.1 Low Power PA
For maximum efficiency, the low power PA should be operated with a maximum VR_PA near 1.35V.
To get VR_PA = 1.35V the user should set TxPower = 14. At this setting:
• The PA can deliver up to 15dBm output power, constant over the specified battery supply range
• The actual maximum output power can be set according to the duty cycle setting (PaDutyCycle)
• If needed, the output power can be decremented in steps of 1dB from maximum by using TxPower < 14
The VR_PA variation over the programmed power TxPower for different supply voltages and PaDutyCycle conditions is
depicted in Figure 9-3: Low Power PA VR_PA Voltage vs. TxPower below (valid for VBAT and VREG supplies, in both LDO or
DCDC configurations).
Note: All figures in this chapter are indicative and typical, and are not a specification. These figures only highlight the
behavior of the PA over the various parameters and conditions.
Figure 9-3: Low Power PA VR_PA Voltage vs. TxPower