RFM42/43
2. Functional Description
The RFM42/43 is low cost ISM wireless transmitter module 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 RFM42/43 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 RFM42‘s PA output power can be configured between +8 and +17 dBm in 3 dB steps, while the RFM43's PA output
power can be configured between –8 and +13 dBm in 3 dB steps. The PA incorporates automatic ramp-up and ramp-down
control to reduce unwanted spectral spreading.
The RFM42/43 is designed to work with a microcontroller 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.
2.1. Operating Modes
The RFM42/43 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 RFM42/43. 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
RFM43
10
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