Pa Output Power; Low Power Pa; Figure 9-5: Low Power Pa Output Power Vs. Txpower - Semtech LR1121 User Manual

9.2 PA Output Power

As stated previously, two parameters do have an impact on the TX output power generated by each 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 must be set to 7. PaHPSel has no impact on either the low power PA or the
high frequency 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 3.7V are superimposed, and only the plots for
3.7V are visible.
For example:
•
TxPower=14 and PaDutyCycle=0 gives +10dBm whatever the supply voltage (1.8V, 3.3V and 3.7V)
•
TxPower=14 and PaDutyCycle=4 gives +14dBm whatever the supply voltage (1.8V, 3.3V and 3.7V)
•
TxPower=14 and PaDutyCycle=7 gives +15dBm whatever the supply voltage (1.8V, 3.3V and 3.7V)
LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
shows the output power of the low power PA with TxPower for
Figure 9-5: Low Power PA Output Power vs. TxPower
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