ADF4106BCP datasheet(9/20 Pages) AD

9 / 20 page

REV. 0

ADF4106

–9–

PRESCALER

P/P + 1

13-BIT B

COUNTER

LOAD

N = BP + A

FROM RF

INPUT STAGE

TO PFD

MODULUS

CONTROL

N DIVIDER

6-BIT A

COUNTER

Figure 4. A and B Counters

R COUNTER

The 14-bit R counter allows the input reference frequency to

be divided down to produce the reference clock to the phase

frequency detector (PFD). Division ratios from 1 to 16,383

are allowed.

PHASE FREQUENCY DETECTOR (PFD) AND

CHARGE PUMP

The PFD takes inputs from the R counter and N counter (N =

BP + A) and produces an output proportional to the phase and

frequency difference between them. Figure 5 is a simplified

schematic. The PFD includes a programmable delay element

which controls the width of the anti-backlash pulse. This pulse

ensures that there is no deadzone in the PFD transfer function

and minimizes phase noise and reference spurs. Two bits in the

Reference Counter Latch, ABP2 and ABP1 control the width of

the pulse. See Table III.

CLR1

CLR2

DOWN

CHARGE

PUMP

ABP2

ABP1

CPGND

R DIVIDER

N DIVIDER

R DIVIDER

N DIVIDER

CP OUTPUT

PROGRAMMABLE

DELAY

Figure 5. PFD Simplified Schematic and Timing (In Lock)

MUXOUT AND LOCK DETECT

The output multiplexer on the ADF4110 family allows the user

to access various internal points on the chip. The state of

MUXOUT is controlled by M3, M2, and M1 in the Function

Latch. Table V shows the full truth table. Figure 6 shows the

MUXOUT section in block diagram form.

Lock Detect

MUXOUT can be programmed for two types of lock detect:

digital lock detect and analog lock detect.

Digital lock detect is active high. When LDP in the R counter

latch is set to 0, digital lock detect is set high when the phase

error on three consecutive Phase Detector cycles is less than

15 ns. With LDP set to “1,” five consecutive cycles of less than

15 ns are required to set the lock detect. It will stay set high

until a phase error of greater than 25 ns is detected on any sub-

sequent PD cycle.

The N-channel open-drain analog lock detect should be oper-

ated with an external pull-up resistor of 10 k

nominal. When

lock has been detected this output will be high with narrow low-

going pulses.

ANALOG LOCK DETECT

MUXOUT

CONTROL

DIGITAL LOCK DETECT

R COUNTER OUTPUT

N COUNTER OUTPUT

SDOUT

MUX

DGND

Figure 6. MUXOUT Circuit

INPUT SHIFT REGISTER

The ADF4110 family digital section includes a 24-bit input shift

6-bit A counter and a 13-bit B counter. Data is clocked into the

24-bit shift register on each rising edge of CLK. The data is

clocked in MSB first. Data is transferred from the shift register

to one of four latches on the rising edge of LE. The destina-

tion latch is determined by the state of the two control bits

(C2, C1) in the shift register. These are the two LSBs, DB1 and

DB0, as shown in the timing diagram of Figure 1. The truth table

for these bits is shown in Table VI. Table I shows a summary

of how the latches are programmed.

Table I. C2, C1 Truth Table

Control Bits

Data Latch

R Counter

N Counter (A and B)

Function Latch (Including Prescaler)

Initialization Latch

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