Semtech LR1121 - High Power PA; Figure 9-9: IDDTX Vs Txpower, Low Power PA, LDO Configuration

LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
92 of 130
Semtech
Proprietary & Confidential
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Figure 9-9: IDDTX vs TxPower, Low Power PA, LDO Configuration
Figure 9-9: IDDTX vs TxPower, Low Power PA, LDO Configuration shows the impact of the supply voltage for three
PaDutyCycle settings (0, 4 and 7) in LDO configuration.
Similarly to the DC-DC configuration, we can see that, at a given supply voltage, a higher PaDutyCycle setting increases the
device current consumption. However, the supply voltage has no influence on the current consumption at a given
PaDutyCycle setting, which means that the plots for 1.8V, 3.3V, and 3.7V are superimposed.
Figure 9-8 and Figure 9-9 show that the power efficiency of the low power PA is maximized when the internal DC-DC
regulator is used at, or above, 3.3V.
9.3.2 High Power PA
Figure 9-10: IDDTX vs TxPower, High Power PA, DC-DC Configuration and Figure 9-11: IDDTX vs TxPower, High Power PA,
LDO Configuration shows the impact of the supply voltage for two PaDutyCycle settings (2 and 4) in both DC-DC and LDO
configurations.
Similarly to the low power PA, at a given supply voltage a higher PaDutyCycle setting increases the device current
consumption. However, at a given PaDutyCycle setting, the current consumption is stable with respect to the supply
voltage, providing this latter is high enough to allow the generation of the VR_PA voltage required for the programmed
power value TxPower.
For example:
• For 3.3V, the current consumption is approx. 98mA for PaDutyCycle=2, and approx. 118mA for PaDutyCycle=4.
• For 1.8V, the current consumption is approx. 69mA for PaDutyCycle=2, and approx. 81mA for PaDutyCycle=4. This is
due to the fact that at 1.8V supply voltage, the maximum VR_PA voltage is 1.6V, therefore a maximum output power of
+17dBm.