si5351 Silicon Laboratories, si5351 Datasheet - Page 13

• Manufacturer Part Number: si5351
• Description: Si5350a Factory-programmable Cmos Clock Generator
• Manufacturer: Silicon Laboratories

4. Configuring the Si5351
The Si5351 is a highly flexible clock generator which is entirely configurable through its I
default configuration is stored in non-volatile memory (NVM) as shown in Figure 10. The NVM is a one time
programmable memory (OTP) which can store a custom user configuration at power-up. This is a useful feature for
applications that need a clock present at power-up (e.g., for providing a clock to a processor).
During a power cycle the contents of the NVM are copied into random access memory (RAM), which sets the
device configuration that will be used during normal operation. Any changes to the device configuration after
power-up are made by reading and writing to registers in the RAM space through the I
register map is shown in Section 9.
A development kit supports field programming which allows writing a custom configuration directly to the NVM.
Since NVM is an OTP memory, it can only be written once. The default configuration is always re-configurable by
writing to RAM through the I
5. Si5351 Application Examples
The Si5351 is a versatile clock generator which serves a wide variety of applications. The following examples show
how it can be used to replace crystals, crystal oscillators, VCXOs, and PLLs.
5.1. Replacing Crystals and Crystal Oscillators
Using an inexpensive external crystal, the Si5351A can generate up to 8 different free-running clock frequencies
for replacing crystals and crystal oscillators. A 3 output version packaged in a small 10-MSOP is also available for
applications that require fewer clocks. An example is shown in Figure 11.
Figure 11. Using the Si5351A to Replace Multiple Crystals, Crystal Oscillators, and PLLs
27 MHz
XA
XB
Si5351A
2
C interface after power up.
OSC
Figure 10. Si5351 Memory Configuration
PLL
Synth
Synth
Synth
Synth
Synth
Synth
Synth
Synth
Multi
Multi
Multi
Multi
Multi
Multi
Multi
Multi
0
1
2
6
7
3
4
5
Default
Config
(OTP)
NVM
Power-Up
Rev. 0.1
CLK0
CLK1
CLK2
CLK3
CLK4
CLK5
CLK6
CLK7
RAM
I
2
74.25/1.001 MHz
C
125 MHz
28.322 MHz
74.25 MHz
24.576 MHz
22.5792 MHz
48 MHz
33.3333 MHz
Controller
Ethernet
HDMI
USB
PHY
Port
CPU
Video/Audio
Processor
Si5351A/B/C
2
C interface. The device’s
2
C interface. A detailed
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