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AD9513

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Table 16. OUT0 Divide or OUT2 Divide

S10

OUT0

Divide (Duty Cycle1)

S2 ≠ 2/3

OUT2

Divide (Duty Cycle1)

S2 = 2/3

7 (43%)

1/3

2 (50%)

11 (45%)

2/3

3 (33%)

13 (46%)

4 (50%)

14 (50%)

1/3

5 (40%)

17 (47%)

1/3

6 (50%)

19 (47%)

2/3

1/3

8 (50%)

20 (50%)

1/3

9 (44%)

21 (48%)

2/3

10 (50%)

22 (50%)

1/3

2/3

12 (50%)

23 (48%)

2/3

15 (47%)

25 (48%)

2/3

16 (50%)

26 (50%)

18 (50%)

27 (48%)

1/3

24 (50%)

28 (50%)

2/3

30 (50%)

29 (48%)

32 (50%)

31 (48%)

1 Duty cycle is the clock signal high time divided by the total period.

DIVIDER PHASE OFFSET

The phase offset of OUT1 and OUT2 can be selected (see Table 13

to Table 15). This allows the relative phase of the outputs 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, tCLK.

Figure 24 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 tCLK.

123

11 12 13

tCLK

CLOCK INPUT

CLK

DIVIDER OUTPUT

DIV = 4

PHASE = 0

PHASE = 1

PHASE = 2

PHASE = 3

tCLK

2 × tCLK

3 × tCLK

Figure 24. Phase Offset—Divider Set for Divide = 4, Phase Set from 0 to 2

For example:

CLK = 491.52 MHz

tCLK = 1/491.52 = 2.0345 ns

For Divide = 4:

Phase Offset 0 = 0 ns

Phase Offset 1 = 2.0345 ns

Phase Offset 2 = 4.069 ns

Phase Offset 3 = 6.104 ns

The outputs can also be described as:

Phase Offset 0 = 0°

Phase Offset 1 = 90°

Phase Offset 2 = 180°

Phase Offset 3 = 270°

Setting the phase offset to Phase = 4 results in the same relative

phase as Phase = 0° or 360°.

The resolution of the phase offset is set by the fast clock period

(tCLK) at CLK. The maximum unique phase offset is less than the

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:

Phase Step = 360°/Divide Ratio

Using some of the same examples:

Divide = 4

Phase Step = 360°/4 = 90°

Unique Phase Offsets in Degrees Are Phase = 0°, 90°,

180°, 270°

Divide = 9

Phase Step = 360°/9 = 40°

Unique Phase Offsets in Degrees Are Phase = 0°, 40°, 80°,

120°, 160°, 200°, 240°, 280°, 320°

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