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RF2052

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 The Operating Frequency

Setting the operating frequency of the device requires a number of registers to be programmed.

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 the VCOSEL and LODIV bits reducing the 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 11.

Set operating

frequencies

Program

P2_VCOSEL and

P2_LODIV

Program

P2_N

Program

P2_NUM_MSB

Program

P2_NUM_LSB,

P2_CT_DEF

Frequency

programmed

3

4

When programming the operating frequency it is

necessary to select the appropriate VCO and LODIV

values. The P2_VCOSEL and P2_LODIV bits are

located in the PLL2x0 register.

If the LO frequency is above 2GHz the LO path current

(CFG5) should be set to 0xC

The integer part of the PLL division ratio is

programmed into the PLL2x3 register.

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

together with the CT_CAL bits if fast frequency

switching is required.

(Depending on required frequency resolution and

coarse tune settings this may not be required.)