RoboClock
CY7B993V
CY7B994V
Document #: 38-07127 Rev. *F
Page 5 of 15
Time Unit Definition
Selectable skew is in discrete increments of time unit (tU). The
value of a tU is determined by the FS setting and the maximum
nominal output frequency. The equation to be used to
determine the tU value is as follows:
tU = 1/(fNOM*N).
N is a multiplication factor which is determined by the FS
setting. fNOM is nominal frequency of the device. N is defined
in Table 2.
Divide and Phase Select Matrix
The Divide and Phase Select Matrix is comprised of five
independent banks: four banks of clock outputs and one bank
for feedback. Each clock output bank has two pairs of
low-skew, high-fanout output buffers ([1:4]Q[A:B][0:1]), two
phase function select inputs ([1:4]F[0:1]), two divider function
selects ([1:4]DS[0:1]), and one output disable (DIS[1:4]).
The feedback bank has one pair of low-skew, high-fanout
output buffers (QFA[0:1]). One of these outputs may connect
to the selected feedback input (FBK[A:B]±). This feedback
bank also has one phase function select input (FBF0), two
divider function selects FSDS[0:1], and one output disable
(FBDIS).
The phase capabilities that are chosen by the phase function
select pins are shown in Table 3. The divide capabilities for
each bank are shown in Table 4.
Figure 1 illustrates the timing relationship of programmable
skew outputs. All times are measured with respect to REF with
the output used for feedback programmed with 0tU skew. The
PLL naturally aligns the rising edge of the FB input and REF
input. If the output used for feedback is programmed to
another skew position, then the whole tU matrix will shift with
respect to REF. For example, if the output used for feedback
is programmed to shift –8tU, then the whole matrix is shifted
forward in time by 8tU. Thus an output programmed with 8tU
of skew will effectively be skewed 16tU with respect to REF.
Notes:
2. The level to be set on FS is determined by the “nominal” operating frequency (fNOM) of the VCO and Phase Generator. fNOM always appears on an output when
the output is operating in the undivided mode. The REF and FB are at fNOM when the output connected to FB is undivided.
3. BK1, BK2 denotes following the skew setting of Bank1 and Bank2, respectively.
Table 1. Frequency Range Select
FS[2]
CY7B993V
CY7B994V
fNOM (MHz)
fNOM (MHz)
Min.
Max.
Min.
Max.
LOW
12
262452
MID
24
52
48
100
HIGH
48
100
96
200
Table 2. N Factor Determination
FS
CY7B993V
CY7B994V
N
fNOM (MHz) at
which tU =1.0 ns
N
fNOM (MHz) at
which tU =1.0 ns
LOW
64
15.625
32
31.25
MID
32
31.25
16
62.5
HIGH
16
62.5
8
125
Table 3. Output Skew Select Function
Function
Selects
Output Skew Function
[1:4]F1
[1:4]F0
and
FBF0
Bank1
Bank2
Bank3
Bank4
Feed-
back
Bank
LOW
LOW
–4tU
–4tU
–8tU
–8tU
–4tU
LOW
MID
–3tU
–3tu
–7tU
–7tU
NA
LOW
HIGH
–2tU
–2tU
–6tU
–6tU
NA
MID
LOW
–1tU
–1tU
BK1[3] BK1[3]
NA
MID
MID
0tU
0tU
0tU
0tU
0tu
MID
HIGH
+1tU
+1tU
BK2[3] BK2[3]
NA
HIGH
LOW
+2tU
+2tU
+6tU
+6tU
NA
HIGH
MID
+3tU
+3tU
+7tU
+7tU
NA
HIGH
HIGH
+4tU
+4tU
+8tU
+8tU
+4tU
Table 4. Output Divider Function
Function
Selects
Output Divider Function
[1:4]DS1
and
FBDS1
[1:4]DS0
and
FBDS0
Bank
1
Bank
2
Bank
3
Bank
4
Feed-
back
Bank
LOW
LOW
/1
/1
/1
/1
/1
LOW
MID
/2
/2
/2
/2
/2
LOW
HIGH
/3
/3
/3
/3
/3
MID
LOW
/4
/4
/4
/4
/4
MID
MID
/5
/5
/5
/5
/5
MID
HIGH
/6
/6
/6
/6
/6
HIGH
LOW
/8
/8/8/8
/8
HIGH
MID
/10
/10
/10
/10
/10
HIGH
HIGH
/12
/12
/12
/12
/12
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