Pa Output Power; Low Power Pa; Figure 9-4: High Power Pa Vr_Pa Voltage Vs. Txpower; Figure 9-5: Low Power Pa Output Power Vs. Txpower - Semtech LR1110 User Manual

For Pout = +20 dBm, VR_PA = 2.5 V is required (brown curve), which means that the High Power PA will be able to maintain
Pout = +20 dBm on the 2.7 V < VBAT < 3.7 V voltage range (2.5 V +200 mV = 2.7V). Below 2.7 V, the output power will
degrade as VBAT reduces.
At 1.8 V of supply voltage, the maximum VR_PA value is 1.6 V (1.8 V - 200 mV), allowing therefore a +17dBm output power.

9.2 PA Output Power

As stated previously, two parameters do have an impact on the TX output power generated by both the Low Power and
the High Power PA: the programmed power TxPower and the duty cycle PaDutyCycle. A third parameter, PaHPSel, controls
the size of the High Power PA, and therefore has a direct impact on the High Power PA output power. In order to reach
+22dBm output power, PaHPSel has to be set to 7. PaHPSel has no impact on the Low Power PA.

9.2.1 Low Power PA

Figure 9-5: Low Power PA Output Power vs. TxPower

different PaDutyCycle settings and over the supply voltage. The supply voltage has no impact on the output power, since
the Low Power PA is internally regulated. Only the PaDutyCycle has an influence on the Output Power. Therefore the plots
for 1.8V, 3.3V and 3.7 V are superimposed, and only the plots for 3.7V are visible.
For example:
•
TxPower=14 and PaDutyCycle=0 gives +10 dBm whatever the supply voltage (1.8V, 3.3V and 3.7 V)
•
TxPower=14 and PaDutyCycle=4 gives +14 dBm whatever the supply voltage (1.8V, 3.3V and 3.7 V)
•
TxPower=14 and PaDutyCycle=7 gives +15dBm whatever the supply voltage (1.8V, 3.3V and 3.7 V)
LR1110
User Manual Rev.1.0
UM.LR1110.W.APP March 2020

Figure 9-4: High Power PA VR_PA Voltage vs. TxPower

shows the output power of the Low Power PA with TxPower for
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