AD9514/PCBZ Analog Devices Inc, AD9514/PCBZ Datasheet - Page 22

• Manufacturer Part Number: AD9514/PCBZ
• Description: 1.5 GHz, 3-Channel MiniDivider Eval Bd
• Manufacturer: Analog Devices Inc

Specifications of AD9514/PCBZ

• Main Purpose: Timing, Clock Distribution
• Utilized Ic / Part: AD9514
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD9514
DIVIDER PHASE OFFSET
The phase of OUT1 or OUT2 can be selected, depending on the
divide ratio and output configuration chosen. This allows, for
example, the relative phase of OUT0 and OUT1 to be set.
After a SYNC operation (see the Synchronization section), the
phase offset word of each divider determines the number of
input clock (CLK) cycles to wait before initiating a clock output
edge. By giving each divider a different phase offset, output-to-
output delays can be set in increments of the fast clock period, t
Figure 29 shows four cases, each with the divider set to divide = 4.
By incrementing the phase offset from 0 to 3, the output is
offset from the initial edge by a multiple of t
DIVIDER OUTPUT
For example:
For Divide = 4:
The outputs can also be described as:
Setting the phase offset to Phase = 4 results in the same relative
phase as Phase = 0° or 360°.
Figure 29. Phase Offset—Divider Set for Divide = 4, Phase Set from 0 to 2
CLOCK INPUT
CLK = 491.52 MHz
t
Phase Offset 0 = 0 ns
Phase Offset 1 = 2.0345 ns
Phase Offset 2 = 4.069 ns
Phase Offset 3 = 6.104 ns
Phase Offset 0 = 0°
Phase Offset 1 = 90°
Phase Offset 2 = 180°
Phase Offset 3 = 270°
CLK
PHASE = 0
PHASE = 1
PHASE = 2
PHASE = 3
= 1/491.52 = 2.0345 ns
DIV = 4
CLK
0
3 × t
1
CLK
t
2
CLK
3
t
2 × t
4
CLK
CLK
5
6
7
8
9
CLK
10
.
11 12
13
14
CLK
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1
5
.
The resolution of the phase offset is set by the fast clock period
(t
divide ratio, up to a phase offset of 15.
Phase offsets can be related to degrees by calculating the phase
step for a particular divide ratio:
Using some of the same examples:
DELAY BLOCK
OUT2 includes an analog delay element that gives variable time
delays (ΔT) in the clock signal passing through that output.
The amount of delay that can be used is determined by the
output frequency. The amount of delay is limited to less than
one-half cycle of the clock period. For example, for a 10 MHz
clock, the delay can extend to the full 10 ns maximum.
However, for a 100 MHz clock, the maximum delay is less than
5 ns (or half of the period).
The AD9514 allows for the selection of three full-scale delays,
1.5 ns, 5 ns, and 10 ns, set by delay full scale (see Table 10). Each
of these full-scale delays can be scaled by 16 fine adjustment
values, which are set by the delay word (see Table 12).
The delay block adds some jitter to the output. This means that
the delay function should be used primarily for clocking digital
chips, such as FPGA, ASIC, DUC, and DDC, rather than for
supplying a sample clock for data converters. The jitter is higher
for longer full scales because the delay block uses a ramp and
trip points to create the variable delay. A longer ramp means
more noise has a chance of being introduced.
CLOCK INPUT
CLK
Phase Step = 360°/Divide Ratio
Divide = 4
Phase Step = 360°/4 = 90°
Unique Phase Offsets in Degrees Are Phase = 0°, 90°,
Divide = 9
Phase Step = 360°/9 = 40°
Unique Phase Offsets in Degrees Are Phase = 0°, 40°, 80°,
) at CLK. The maximum unique phase offset is less than the
180°, 270°
120°, 160°, 200°, 240°, 280°, 320°
∅SELECT
÷N
Figure 30. Analog Delay Block
FULL SCALE : 1.5ns, 5ns, 10ns
FINE DELAY ADJUST
(16 STEPS)
ΔT
OUT2 ONLY
CMOS
LVDS
OUTPUT
DRIVER