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KC705 Evaluation Board
25
UG810 (v1.3) May 10, 2013
Feature Descriptions
For more about the Si Time SiT9102 see
.
Programmable User Clock Source
[
, callout
]
The KC705 board has a programmable low-jitter 3.3V differential oscillator (U45) the
FPGA MRCC inputs of bank 15. This USER_CLOCK_P and USER_CLOCK_N clock signal
pair are connected to FPGA U1 pins K28 and K29 respectively. On power-up the user clock
defaults to an output frequency of 156.250 MHz. User applications can change the output
frequency within the range of 10 MHz to 810 MHz through an I
2
C interface. Power cycling
the KC705 board will revert the user clock to its default frequency of 156.250 MHz.
•
Programmable Oscillator: Silicon Labs Si570BAB0000544DG (10 MHz - 810 MHz)
•
Differential Output
•
I
2
C address
0x5D
The user clock circuit is shown in
.
For more information about the Silicon Labs Si570 see
X-Ref Target - Figure 1-10
Figure 1-10:
System Clock Source
UG810_c1_09_120211
GND
VCC2V5
SIT9102
200 MHz
Oscillator
OE
NC
GND
VCC
OUT_B
OUT
1
2
3
6
5
4
U6
R459
100
Ω
1%
SYSCLK_P
SYSCLK_N
C550
0.1
μ
F 10V
X5R
X-Ref Target - Figure 1-11
Figure 1-11:
User Clock Source
UG810_c1_10_011212
GND
VCC3V3
Si570
Programmable
Oscillator
NC
OE
GND
SCL
SDA
VDD
1
2
3
8
7
6
U45
R8
4.7K
Ω
5%
USER CLOCK N
C77
0.01
μ
F 25V
X7R
CLK-
4
5
GND
VCC3V3
CLK+
USER CLOCK P
USER CLOCK SDA
USER CLOCK SCL
10 MHz - 810 MHz
50 PPM
To I2C
Bus Switch
(U49)