Pa Supply Scheme; Figure 9-2: Pa Block Diagram - Semtech LR1110 User Manual

9.1 PA Supply Scheme

The PA supply scheme is depicted in
The PA regulator (Reg_PA) is used to supply of both the Low Power PA and the High Power PAs through the VR_PA pin.
Each amplifier require a high-Q choke inductor connected externally between their respective output and VR_PA in order
to provide the bias and control the output power.
The PA regulator is internally connected to the DC-DC /LDO output for the Low Power PA, allowing a +15dBm operation in
both DCDC or LDO configurations. It is also connected to the VBAT_RF pin for the High Power PA, therefore to the main
supply voltage. This means that the maximum output power generated by the High Power PA will depend on the VBAT
voltage.
The TX main supply can switched between the battery VBAT and the internal regulator VREG, according to the PA use case.
When operating with VR_PA above 1.35 V (e.g. in the case of High Power), the battery supply VBAT must be chosen. When
operating with VR_PA below 1.35 V (e.g. in the case of low power PA), either supply can be chosen. However, it is better to
choose the internal regulator VREG whenever the required VR_PA is 1.35 V or below, in order to benefit from the Buck
converter.
The LR1110 incorporates a precise duty cycle trimmer shared between the two power amplifiers. This duty cycle trimmer
can be used to trade-off the output power, efficiency, and harmonic emission to address the different regional standard
requirements.
LR1110
User Manual Rev.1.0
UM.LR1110.W.APP March 2020
Figure 9-2: PA Block Diagram.

Figure 9-2: PA Block Diagram

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