RF42/43
2. Functional Description
The RF42/43 is a 100% CMOS ISM wireless transmitter with continuous frequency tuning over the complete 240–930 MHz
band. The wide operating voltage range of 1.8–3.6 V and low current consumption makes the RF42/43 and ideal solution for
battery powered applications.
A high precision local oscillator (LO) is used for transmit mode. The LO is generated by an integrated VCO and
△∑Fractional-N PLL synthesizer. The synthesizer is designed to support configurable data rates, output frequency,frequency
deviation, and Gaussian filtering at any frequency between 240–930 MHz. The transmit FSK data is modulated directly into
the △∑data stream and can be shaped by a Gaussian low-pass filter to reduce unwanted spectral content.
The RF42‘s PA output power can be configured between +11 and +20 dBm in 3 dB steps, while the RF43's PA output power
can be configured between –8 and +13 dBm in 3 dB steps. The PA is single-ended to allow for easy antenna matching and
low BOM cost. The PA incorporates automatic ramp-up and ramp-down control to reduce unwanted spectral spreading.
The RF42/43 is designed to work with a microcontroller, crystal, and a few passives to create a very low cost system. Voltage
regulators are integrated on-chip which allow for a wide range of operating supply voltage conditions from +1.8 to +3.6 V. A
standard 4-pin SPI bus is used to communicate with the microcontroller. Three configurable general purpose I/Os are
available for use to tailor towards the needs of the system. A more omplete list of the available GPIO functions is shown in "7.
Auxiliary Functions" but just to name a few, microcontroller clock output, POR, and specific interrupts. A limited number of
passive components are needed to match the PA. Refer to Figure 20, ―RF43 Reference Design Schematic,‖.
2.1. Operating Modes
The RF42/43 provides several modes of operation which can be used to optimize the power consumption of the device
application.
Table 8 summarizes the modes of operation of the RF42/43. In general, any given mode of operation may be classified as an
Active mode or a Power Saving mode. The table indicates which block(s) are enabled (active) in each corresponding mode.
With the exception the Shutdown mode, all can be dynamically selected by sending the appropriate commands over the SPI
in order to optimize the average current consumption. An ―X‖ in any cell means that, in the given mode of operation, that block
can be independently programmed to be either ON or OFF, without noticeably affecting the current consumption. The SPI
circuit block includes the SPI interface and the register space. The 32 kHz OSC circuit block includes the 32.768 kHz RC
oscillator or 32.768 kHz crystal oscillator, and wake-up timer. AUX (Auxiliary Blocks) includes the temperature sensor,
general purpose ADC, and low-battery detector.
Table 8. Operating Modes
RF43
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