rf2057 RF Micro Devices, rf2057 Datasheet - Page 20

• Manufacturer Part Number: rf2057
• Description: High Performance Wideband Rf Pll/vco With Integrated Rf Mixers For Repeaters
• Manufacturer: RF Micro Devices

RF2057
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.
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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2
Operating mode set
Enable loop filter
Default
Default
Set calibration
coarse tune?
Disable VCO
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mode
cal?
Yes
Yes
3
P1_CT_EN,
calibration
P2_CT_EN
Loop filter
Set to 00
When setting up the device it is necessary to decide
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.
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.
DS091109