RF2053
Setting The Operating Frequency
Setting the operating frequency of the device requires a number of registers to be programmed.
Set operating
frequencies
3
When programming the operating frequency it is
necessary to select the appropriate LODIV value,
located in the PLL2x0 register. If the LO frequency is
above 2GHz the LO path current (CFG5) should be set
Program P2_LODIV
and LO2_I
to 0xC.
Program
P2_N
The integer part of the PLL division ratio is
programmed into the PLL2x3 register.
Program
P2_NUM_MSB
The MSB of the fractional part of the synthesizer PLL
divider value is programmed into the PLL2x1 register.
The LSB of the fractional part of the synthesizer PLL
divider value is programmed into the PLL2x2 register.
Program
P2_NUM_LSB
Frequency
programmed
4
A total of four registers must be programmed to set the device operating frequency. This will take 5.2us for each path at maxi-
mum clock speed.
To change the frequency of the VCO it will be necessary to repeat these operations. However, if the frequency shift is small it
may not be necessary to reprogram all the bits reducing the number of register writes to three.
For an example on how to determine the integer and fractional parts of the synthesizer PLL division ratio please refer to the
detailed description of the PLL on page 9.
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