RF96 datasheet(78/121 Pages) HOPE

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Page 78

RF96/97/98

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WIRELESS & SENSING

PRELIMINARY

DATASHEET

5.4. Transmitter Description

The transmitter of RF96/97/98 comprises the frequency synthesizer, modulator (both LoRaTM and FSK/OOK) and power

amplifier blocks, together with the DC biasing and ramping functionality that is provided through the VR_PA block.

5.4.1. Architecture Description

The architecture of the RF front end is shown in the following diagram.

Figure 40. RF Front-end Architecture Shows the Internal PA Configuration.

5.4.2. RF Power Amplifiers

PA_HF and PA_LF are high efficiency amplifiers capable of yielding RF power programmable in 1 dB steps from -4 to

+14dBm directly into a 50 ohm load with low current consumption. PA_LF covers the lower bands (up to 525 MHz), whilst

PA_HF will cover the upper bands (from 860 MHz). The output power is sensitive to the power supply voltage, and typically

their performance is expressed at 3.3V.

PA_HP (High Power), connected to the PA_BOOST pin, covers all frequency bands that the chip addresses. It permits

continuous operation at up to +17 dBm and duty cycled operation at up to +20dBm. For full details of operation at +20dBm

please consult Section 5.4.3

Table 77 Power Amplifier Mode Selection Truth Table

PaSelect

Mode

Power Range

Pout Formula

PA_HF or PA_LF on RFO_HF or RFO_LF

-4 to +15dBm

Pout=Pmax-(15-OutputPower)

Pmax=10.8+0.6*MaxPower [dBm]

PA_HP on PA_BOOST, any frequency

+2 to +17dBm

Pout=17-(15-OutputPower) [dBm]

Notes - For +20 dBm restrictions on operation please consult the following section.

- To ensure correct operation at the highest power levels ensure that the current limiter OcpTrim is adjusted to

permit delivery of the requisite supply current.

- If the PA_BOOST pin is not used it may be left floating.

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