SI5356A Datasheet, PDF (11/29 Pages) Silicon Laboratories – IC PROGRAMMABLE, ANY-FREQUENCY 1–200 MHZ, QUAD FREQUENCY 8-OUTPUT CLOCK GENERATOR

Si5356A
MultiSynth
Fractional-N
f_VCO
Divider
Phase
Adjust
f_OUT
Phase Error
Calculator
Divider Select
(DIV1, DIV2)
Figure 3. Silicon Labs' MultiSynth Technology
3.4. Frequency Configuration
The Si5356 utilizes a single PLL-based architecture,
four independent MultiSynth fractional output dividers,
and a MultiSynth fractional feedback divider such that a
single device provides the clock generation capability of
four independent PLLs. Unlike competitive multi-PLL
solutions, the Si5356 can generate four unique non-
integer related output frequencies with 0 ppm frequency
error, with respect to the reference, for any combination
of output frequencies. In addition, any combination of
output frequencies can be generated from a single
reference frequency without having to change the
crystal or reference clock frequency between
configurations.
Frequency configurations are fully programmable by
writing to device registers using the I²C interface. Any
combination of output frequencies ranging from 1 to
200 MHz can be configured on each of the device
outputs.
3.5. Configuring the Si5356
The Si5356 is a highly-flexible clock generator that is
entirely configurable through its I²C interface. The
device’s default configuration is stored in non-volatile
memory (NVM) as shown in Figure 4. 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).
Power-Up/POR
NVM
(OTP)
Default
Config
RAM
I²C
Figure 4. Si5356 Memory Configuration
During a power cycle or a power-on reset (POR), the
contents of the NVM are copied into random access
memory (RAM), which sets the device configuration that
will be used during operation. Any changes to the
device configuration after power-up are made by
reading and writing to registers in the RAM space
through the I²C interface. ClockBuilder Desktop (see
"3.1.1. ClockBuilder™ Desktop Software" on page 9)
can be used to easily configure register map files that
can be written into RAM (see “3.5.2. Creating a New
Configuration for RAM” for details). Alternatively, the
register map file can be created manually with the help
of the equations in AN565.
Two versions of the Si5356 are available. First, non-
customized Si5356 devices are available in which the
RAM can be configured in-circuit via I²C. These blank
Si5356 devices can also be field programmed using the
Si5338/56-PROG-EVB (see “3.5.4. Writing a Custom
Configuration to NVM”). Second, custom factory-
programmed Si5356 devices are available that include
a user-specified startup frequency configuration
(example part number Si5356A-Axxxxx-GM).
Rev. 1.3
11