ADF4208BRUZ-R7 datasheet(19/24 Pages) AD

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ADF4206/ADF4208

Rev. A | Page 19 of 24

RF2 Prescaler Value

P6 in the RF2 AB counter latch sets the RF2 prescaler value.

See Figure 29.

RF2 Power-Down

P7 in Figure 29 is the power-down bit for the RF2 side.

RF SECTION (RF1)

Programmable RF1 Reference (R) Counter

If Control Bit C2 and Control Bit C1 are 1 and 0, the data is

transferred from the input shift register to the 14-bit RF1 R

counter. Figure 30 shows the input shift register data format for

the RF1 R counter and the divide ratios that are possible.

RF1 Phase Detector Polarity

P9 sets the RF1 phase detector polarity. When the RF1 VCO

characteristics are positive this is set to 1. When negative it is set

to 0. See Figure 30.

RF1 Charge Pump Three-State

P10 puts the RF1 charge pump into three-state mode when

programmed to a 1. It is set to 0 for normal operation.

See Figure 30.

RF1 Program Modes

Figure 28 and Figure 30 show how to set up the program modes

in the ADF420x family.

RF1 Charge Pump Currents

Bit P13 programs the current setting for the RF1 charge pump.

See Figure 30.

Programmable RF1 AB Counter

If Control Bit C2 and Control Bit C1 are 1 and 1, then the data

in the input register is used to program the RF1 AB counter.

The AB counter is a 6-bit swallow counter (A counter) and

11-bit programmable counter (B counter). Figure 31 shows the

input register data format for programming the RF1 AB counter

and the divide ratios that are possible.

RF1 Prescaler Value

P14 in the RF1 A, B counter latch sets the RF1 prescaler value.

See Figure 31.

RF1 Power-Down

Setting P16 in the RF1 AB counter high powers down RF1 side.

RF Fast Lock

The fast lock feature improves the lock time of the PLL. It

increases charge pump current to a maximum for a time.

Activate fast lock of the ADF420x family by setting P13 in the

reference counter high and setting the fast lock switch on using

MUXOUT. Switching in an external resistor using MUXOUT

compensates the loop dynamics for the effect of increasing

charge pump current. Setting P13 low removes the PLL from

fast lock mode.

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