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KC705 Evaluation Board
UG810 (v1.3) May 10, 2013
Chapter 1:
KC705 Evaluation Board Features
Jitter Attenuated Clock
[
, callout
]
The KC705 board includes a Silicon Labs Si5324 jitter attenuator U70 on the back side of the
board. FPGA user logic can implement a clock recovery circuit and then output this clock
to a differential I/O pair on I/O bank 13 (REC_CLOCK_C_P, FPGA U1 pin W27 and
REC_CLOCK_C_N, FPGA U1 pin W28) for jitter attenuation. The jitter attenuated clock
(SI5326_OUT_C_P, SI5326_OUT_C_N) is then routed as a reference clock to GTX Quad 116
inputs MGTREFCLK0P (FPGA U1 pin L8) and MGTREFCLK0N (FPGA U1 pin L7).
The primary purpose of this clock is to support CPRI/OBSAI applications that perform
clock recovery from a user-supplied SFP/SFP+ module and use the jitter attenuated
recovered clock to drive the reference clock inputs of a GTX transceiver. The jitter
attenuated clock circuit is shown in
For more information about the Silicon Labs Si5324 see
.
X-Ref Target - Figure 1-14
Figure 1-14:
Jitter Attenuated Clock
UG
8
10_c1_1
3
_101012
R424
4.7K
Ω
5%
S
I5
3
26_VCC
S
i5
3
24C-C-GM
Clock M
u
ltiplier/
Jitter Atten
ua
tor
VDDA
GND
XB
XA
NC5
3
2
6
5
29
2
8
U70
CKOUT1_N
7
8
CKOUT1_P
C47
3
0.1
μ
F 25V
X5R
C474
0.1
μ
F 25V
X5R
S
I5
3
26_XTAL_XA
GND2
GND1
XB
XA
X5
114.2
8
5 MHz
20 ppm
S
I5
3
26_OUT_C_N
S
I5
3
26_OUT_C_P
S
I5
3
26_OUT_N
S
I5
3
26_OUT_P
S
I5
3
26_XTAL_XB
GND
NC4
2
1
3
4
C475
0.1
μ
F 25V
X5R
C476
0.1
μ
F 25V
X5R
REC_CLOCK_P
REC_CLOCK_N
REC_CLOCK_C_P
REC_CLOCK_C_N
16
17
R
33
7
100
Ω
CKIN1_P
CKIN1_N
NC
NC
12
1
3
CKIN2_P
CKIN2_N
10
5
VDDA
VDDA
2
NC
3
2
NC2
2
NC1
NC
NC
NC
NC
NC
3
5
3
4
NC
NC
CKOUT2_N
CKOUT2_P
S
I5
3
26_INT_ALM
3
NC
4
NC 11
NC 15
NC 1
8
NC 19
NC 20
S
I5
3
26_R
S
T
1
21
3
1
GND2
9
GND1
3
1
A2_
SS
3
1
A1
24
A0
22
S
I5
3
26_
S
CL
S
CL
2
3
S
I5
3
26_
S
DA
S
DA_
S
DO
27
NC
S
DI
3
6
CMODE
GND
INC
DEC
LOL
RATE1
RATE0
C2B
INT_C1B
C
S
_CA
R
S
T_B
3
7
GNDPAD