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RF2051

DS140110

7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical

support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.

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).

Disable VCO

coarse tune?

Default

Yes

P1_CT_EN,

P2_CT_EN

Set to 00

Set calibration

mode

Operating mode set

Enable loop filter

cal?

Default

Yes

Loop filter

calibration

2

3

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.