AX8052F151 datasheet(35/51 Pages) ONSEMI

35 / 51 page

Transceiver

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AX8052F151

Transceiver

The transceiver block is controllable through its registers, which are mapped into the X data space

the microcontroller. The transceiver block features its own 4 word × 10 bit FIFO. The

microcontroller can either be interrupted at a programmable FIFO fill level, or one of the DMA

channels can be instructed to transfer between XRAM and the transceiver FIFO.

6.1. RF Frequency Generation Subsystem

The RF frequency generation subsystem consists of a fully integrated synthesizer, which multiplies

the reference frequency from the crystal oscillator to get the desired RF frequency. The advanced

architecture of the synthesizer enables frequency resolutions of 1 Hz, as well as fast settling times

of 5 – 50 µs depending on the settings (see section 4.3: AC Characteristics). Fast settling times

mean fast start-up and fast RX/TX switching, enabling low-power system design.

For receive operation the RF frequency is fed to the mixer, for transmit operation to the power-

amplifier.

The frequency must be programmed to the desired carrier frequency. The RF frequency shift by

the IF frequency that is required for RX operation, is automatically set when the receiver is

activated and does not need to be programmed by the user. The default IF frequency is 1 MHz. It

can be programmed to other values. Changing the IF frequency and thus the centre frequency of

the digital channel filter can be used to adapt the blocking performance of the device to specific

system requirements.

The synthesizer loop bandwidth can be programmed. This serves three purposes:

1. Start-up time optimization, start-up is faster for higher synthesizer loop bandwidths

2. TX spectrum optimization, phase-noise at 300 kHz to 1 MHz distance from the carrier

improves with lower synthesizer loop bandwidths

3. Adaptation of the bandwidth to the data-rate. For transmission of FSK and MSK it is

required that the synthesizer bandwidth must be in the order of the data-rate.

VCO

An on-chip VCO converts the control voltage generated by the charge pump and loop filter into an

output frequency. This frequency is used for transmit as well as for receive operation. The

frequency can be programmed in 1 Hz steps in the

AX5051_FREQ registers. For operation in the

433 MHz band, the BANDSEL bit in the

AX5051_PLLLOOP register must be programmed.

VCO Auto-Ranging

The AX8052F151 has an integrated auto-ranging function, which allows to set the correct VCO

range for specific frequency generation subsystem settings automatically. Typically it has to be

executed after power-up. The function is initiated by setting the RNG_START bit in the

AX5051_PLLRANGING register. The bit is readable and a 0 indicates the end of the ranging

process. The RNGERR bit indicates the correct execution of the auto-ranging.

AX8052F151 Datasheet(PDF) 35 Page - ON Semiconductor