RF2051
Setting Up VCO Coarse Tuning and Loop Filter Calibration
If the user wishes to disable the VCO coarse tune calibration or enable the loop filter calibration then the following program-
ming operation will need to take place.
Set calibration
2
mode
When setting up the device it is necessary to decide
P1_CT_EN,
P2_CT_EN
Set to 00
whether to deactivate the devices' internal VCO
calibration or provide the calibration information
directly. These bits are located in the PLL1x0 and
PLL2x0 registers and are active by default.
Disable VCO
coarse tune?
Yes
Yes
Default
It is also necessary to decide whether to activate the
loop filter calibration mode, only necessary when
operating the device over very wide band of
frequencies. These bits are also located in the PLL1x0
and PLL2x0 registers. The default setting assumes an
active loop filter is used.
Enable loop filter
cal?
Loop filter
calibration
Default
Operating mode set
3
Two registers need to be written taking 2.6us at maximum clock speed if the course tuning is deactivated or the loop filter cal-
ibration activated. Since it is necessary to program these registers when setting the operating frequency (see next section) this
operation usually carries no overhead.
The coarse tune calibration takes approximately 50us when using a 26MHz reference clock (it will take proportionally longer if
a slower clock is used, and vice versa).
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