ADF4110/ADF4111/ADF4112/ADF4113
Lock Detect
PHASE FREQUENCY DETECTOR (PFD) AND
CHARGE PUMP
MUXOUT can be programmed for two types of lock detect:
digital lock detect and analog lock detect.
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 31 is a simplified
schematic. The PFD includes a programmable delay element
that controls the width of the antibacklash pulse. This pulse
ensures that there is no dead zone 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 7.
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 (PD) 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 stays high until
a phase error greater than 25 ns is detected on any subsequent
PD cycle.
The N-channel open-drain analog lock detect should be
operated with a 10 kΩ nominal external pull-up resistor. When
lock has been detected, this output is high with narrow low-
going pulses.
V
P
CHARGE
PUMP
UP
HI
D1
Q1
U1
DV
DD
R DIVIDER
CLR1
ANALOG LOCK DETECT
DIGITAL LOCK DETECT
R COUNTER OUTPUT
N COUNTER OUTPUT
SDOUT
PROGRAMMABLE
DELAY
CP
U3
MUXOUT
MUX
CONTROL
ABP1
ABP2
CLR2
U2
DOWN
HI
D2
Q2
DGND
N DIVIDER
Figure 32. MUXOUT Circuit
CPGND
R DIVIDER
N DIVIDER
CP OUTPUT
INPUT SHIFT REGISTER
The ADF4110 family digital section includes a 24-bit input shift
register, a 14-bit R counter, and a 19-bit N counter comprised of
a 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 MSB first. Data
is transferred from the shift register to one of four latches on
the rising edge of LE. The destination 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 Figure 2. The truth
table for these bits is shown in Table 5.
Figure 31. 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 9 shows the full truth table. Figure 32 shows the
MUXOUT section in block diagram form.
Table 6 shows a summary of how the latches are programmed.
Table 5. C2, C1 Truth Table
Control Bits
C2
0
C1
0
Data Latch
R Counter
0
1
1
1
0
1
N Counter (A and B)
Function Latch (Including Prescaler)
Initialization Latch
Rev. C | Page 13 of 28
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