AD9520-3/PCBZ Analog Devices Inc, AD9520-3/PCBZ Datasheet - Page 37

• Manufacturer Part Number: AD9520-3/PCBZ
• Description: 12/24 Channel Clock Gen 2,0GH
• Manufacturer: Analog Devices Inc

Specifications of AD9520-3/PCBZ

• Design Resources: Synchronizing Multiple AD9910 1 GSPS Direct Digital Synthesizers (CN0121) Phase Coherent FSK Modulator (CN0186)
• Main Purpose: Timing, Clock Generator
• Utilized Ic / Part: AD9520-3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Prescaler
The prescaler of the AD9520 allows for two modes of operation:
a fixed divide (FD) mode of 1, 2, or 3, and a dual modulus
(DM) mode where the prescaler divides by P and (P + 1) {2 and
3, 4 and 5, 8 and 9, 16 and 17, or 32 and 33}. The prescaler
modes of operation are given in Table 53, 0x016[2:0]. Not all
modes are available at all frequencies (see Table 2).
When operating the AD9520 in dual modulus mode, P/(P + 1),
the equation used to relate the input reference frequency to the
VCO output frequency is
However, when operating the prescaler in FD Mode 1,
FD Mode 2, or FD Mode 3, the A counter is not used (A = 0)
and the equation simplifies to
When A = 0, the divide is a fixed divide of P = 2, 4, 8, 16, or 32.
By using combinations of DM and FD modes, the AD9520 can
achieve values of N all the way down to N = 1. Table 29 shows
how a 10 MHz reference input can be locked to any integer
multiple of N.
Note that the same value of N can be derived in different ways,
as illustrated by the case of N = 12. The user can choose a fixed
divide mode P = 2 with B = 6, use the dual modulus mode 2/3
with A = 0, B = 6, or use the dual modulus mode 4/5 with
A = 0, B = 3.
Table 29. How a 10 MHz Reference Input Can Be Locked to Any Integer Multiple of N
f
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
1
REF
X = don’t care.
(MHz)
f
f
VCO
VCO
= (f
= (f
REF
REF
R
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
/R) × (P × B + A) = f
/R) × (P × B) = f
P
1
2
1
1
1
2
2
2
2
2
2
2
2
2
2
4
4
A
X
X
X
X
X
X
0
1
2
1
X
0
1
X
0
0
1
1
1
1
1
1
1
1
1
REF
× N/R
B
1
1
3
4
5
3
3
3
3
4
5
5
5
6
6
3
3
REF
× N/R
N
1
2
3
4
5
6
6
7
8
9
10
10
11
12
12
12
13
f
10
20
30
40
50
60
60
70
80
90
100
100
110
120
120
120
130
VCO
(MHz)
Rev. 0 | Page 37 of 84
Mode
FD
FD
FD
FD
FD
FD
DM
DM
DM
DM
FD
DM
DM
FD
DM
DM
DM
A and B Counters
The AD9520 B counter can be bypassed (B = 1). This B counter
bypass mode is valid only when using the prescaler in FD mode.
When A = 0, the divide is a fixed divide of P = 2, 4, 8, 16, or 32.
Unlike the R counter, A = 0 is actually zero. The B counter must
be ≥3 or bypassed.
The maximum input frequency to the A/B counter is reflected
in the maximum prescaler output frequency (~300 MHz) specified
in Table 2. This is the prescaler input frequency (VCO or CLK)
divided by P.
Although manual reset is not normally required, the A/B counters
have their own reset bit. The A and B counters can be reset using
the shared reset bit of the R, A, and B counters. They can also
be reset through a SYNC operation.
R, A, and B Counters: SYNC Pin Reset
The R, A, and B counters can also be reset simultaneously through
the SYNC pin. This function is controlled by 0x019[7:6] (see
Table 53
R and N Divider Delays
Both the R and N dividers feature a programmable delay cell.
These delays can be enabled to allow adjustment of the phase
relationship between the PLL reference clock and the VCO or
CLK. Each delay is controlled by three bits. The total delay
range is about 1 ns. See 0x019 in Table 53.
). The
Notes
P = 1, B = 1 (bypassed)
P = 2, B = 1 (bypassed)
P = 1, B = 3
P = 1, B = 4
P = 1, B = 5
P = 2, B = 3
P and P + 1 = 2 and 3, A = 0, B = 3
P and P + 1 = 2 and 3, A = 1, B = 3
P and P + 1 = 2 and 3, A = 2, B = 3
P and P + 1 = 2 and 3, A = 1, B = 4
P = 2, B = 5
P and P + 1 = 2 and 3, A = 0, B = 5
P and P + 1 = 2 and 3, A = 1, B = 5
P = 2, B = 6
P and P + 1 = 2 and 3, A = 0, B = 6
P and P + 1 = 4 and 5, A = 0, B = 3
P and P + 1 = 4 and 5, A = 1, B = 3
SYNC pin reset is disabled by default.
AD9520-3