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RF68

1. Circuit Description

1.1. General Description

The RF68 is a fully-integrated multi-band, single chip transmitter IC capable of FSK and OOK modulation of an input

data stream.

It contains a frequency synthesizer which is a fractional-N sigma-delta PLL. For frequency modulation (FSK), the

modulation is made inside the PLL bandwidth. For amplitude modulation (OOK), the modulation is performed by turning on

and off the output PA.

The frequency reference used by the PLL is generated by a 22, 24 or 26 MHz crystal oscillator, depending on the

frequency band of interest.

The Power Amplifier (PA), connected to the RFOUT pin, can deliver 0 dBm or +10 dBm in a 50

Ω load. Each of these two

output powers need a specific matching network when efficiency needs to be optimized.

The circuit can be configured via a simplified TWI interface, constituted of pin CTRL and DATA. The pins of this interface

are also used to transmit the modulating data to the chip.

Another key feature of the RF68 is its low current consumption in Transmit and Sleep modes and its wide voltage

operating range from 1.8 V to 3.7 V. This makes the RF68 suitable for low-cost battery chemistries or energy harvesting

applications.

1.2. Block Diagram

The figure below shows the simplified block diagram of the RF68 die mounted in a DFN8 package.

Figure 1. RF68 Simplified Block Diagram and BOM