AXM0F243 datasheet(34/53 Pages) ONSEMI

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AXM0F243

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Registers

Table 46. RF FREQUENCY GENERATION REGISTERS

Bits

Purpose

AX5043_PLLLOOP

AX5043_PLLLOOPBOOST

FLT[1:0]

Synthesizer loop filter bandwidth and selection of external loop filter, recommended usage is to

increase the bandwidth for faster settling time, bandwidth increases of factor 2 and 5 are possi-

ble.

AX5043_PLLCPI

AX5043_PLLCPIBOOST

Synthesizer charge pump current, recommended usage is to decrease the bandwidth (and

improve the phase−noise) for low data−rate transmissions.

AX5043_PLLVCODIV

REFDIV

Sets the synthesizer reference divider ratio.

RFDIV

Sets the synthesizer output divider ratio.

VCOSEL

Selects either the internal or the external VCO

VCO2INT Selects either the internal VCO inductor or an external inductor between pins L1 and L2

AX5043_FREQA, AX5043_FREQB

Programming of the carrier frequency

AX5043_PLLRANGINGA,

AX5043_PLLRANGINGB

Initiate VCO auto−ranging and check results

RF Input and Output Stage (ANTP/ANTN/ANTP1)

The AXM0F243 has two main antenna interface modes:

1. Both RX and TX use differential pins ANTP and

ANTN. RX/TX switching is handled internally.

This mode is recommended for highest output

powers, highest sensitivities and for direct

connection to dipole antennas. Also see Figure 10.

2. RX uses the differential antenna pins ANTP and

ANTN. TX uses the single ended antenna pin

ANTP1. RX/TX switching is handled externally.

This can be done either with an external RX/TX

switch or with a direct tie configuration. This

mode is recommended for low output powers at

high efficiency Figure 13 and for usage with

external power amplifiers Figure 12.

When antenna diversity is enabled, the radio controller

will, when not in the middle of receiving a packet,

periodically probe both antennas and select the antenna with

the highest signal strength. The radio controller can be

instructed to periodically write both RSSI values into the

FIFO. Antenna diversity mode is fully automatic.

LNA

The LNA amplifies the differential RF signal from the

antenna and buffers it to drive the I/Q mixer. An external

matching network is used to adapt the antenna impedance to

the IC impedance. A DC feed to GND must be provided at

the antenna pins.

In TX mode the PA drives the signal generated by the

frequency generation subsystem out to either the differential

antenna terminals or to the single ended antenna pin. The

antenna terminals are chosen via the bits TXDIFF and TXSE

in register AX5043_MODECFGA.

The output power of the PA is programmed via the register

AX5043_TXPWRCOEFFB.

The PA can be digitally pre−distorted for high linearity.

The output amplitude can be shaped (raised cosine), this

mode is selected with bit AMPLSHAPE in register

AX5043_MODECFGA PA ramping is programmable in

increments of the bit time and can be set to 1 – 8 bit times via

bits SLOWRAMP in register AX5043_MODECFGA

Output power as well as harmonic content will depend on

the external impedance seen by the PA.

Digital IF Channel Filter and Demodulator

The digital IF channel filter and the demodulator extract

the data bit−stream from the incoming IF signal. They must

be programmed to match the modulation scheme as well as

the data−rate. Inaccurate programming will lead to loss of

sensitivity.

The channel filter offers bandwidths of 995 Hz up to

221 kHz.

The RadioLab Software calculates the necessary register

settings for optimal performance. An overview of the

registers involved is given in the following table as

reference, for details see the AX5043 Programming

Manual. The register setups typically must be done once at

power−up of the device.

AXM0F243 Datasheet(PDF) 34 Page - ON Semiconductor

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