SI5315-EVB Silicon Laboratories Inc, SI5315-EVB Datasheet - Page 3

• Manufacturer Part Number: SI5315-EVB
• Description: BOARD EVAL SI5315 8KHZ-644.53MHZ
• Manufacturer: Silicon Laboratories Inc

Specifications of SI5315-EVB

• Main Purpose: Timing, Clock Multiplier
• Embedded: No
• Utilized Ic / Part: SI5315
• Primary Attributes: 2 Inputs, 2 Outputs
• Secondary Attributes: CML, CMOS, LVDS, LVPECL
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

2. Si53315-EVB Input and Output Clocks
Refer to the schematics, diagrams, and tables while reading this section.
2.1. Input Clocks
The Si5315 has two differential clock inputs that are AC terminated and AC coupled before being presented to the
Si5315. If the input clock frequencies are low (below 1 MHz), there are extra considerations that should be taken
into account. The Si5315 has a maximum clock input rise time specification of 11 ns that must be met (see CKNtrf
in the Si5315 data sheet). Also, if the input clock is LVCMOS, it might be advantageous to replace the input
coupling capacitors (C7, C12, C16, and C18) with zero ohm resistors. Regardless of the input format, if the clock
inputs are not roughly 50% duty cycle, it is highly recommended to avoid AC coupling. For input clocks that are far
off of 50% duty cycle, the average value of the signal that passes through the coupling capacitor will be significantly
off of the midpoint between the maximum and minimum value of the clock signal, resulting in a mismatch with the
common mode input threshold voltage (see V
2.2. XA-XB Reference
To achieve very low jitter generation and for stability during holdover, the Si5315 requires a stable, low jitter
reference at its XA-XB pins. To that end, the EVB is configured with a 40 MHz fundamental mode crystal connected
between pins 6 and 7 of the Si5315. However, the Si5315-EVB is capable of using an external XA-XB reference
oscillator, either differential or single ended. J1 and J2 are the SMA connectors with AC termination. AC coupling is
also provided that needs to be installed at C6 and C8. Table 1 explains the changes of components that are
needed to implement an external XA-XB reference oscillator.
2.3. Output Clocks
The clock outputs are AC coupled and are available on SMA's J5, J7, J9, and J11. For LVCMOS outputs, it might
be desirable to replace the AC coupling capacitors (C9, C14, C17, and C 20) with zero ohm resistors. Also, if
greater drive strength is desired for LVCMOS outputs, R6 and R10 can be installed.
Ext Ref In+
Ext Ref In-
C6, C8
R8
XTAL/CLOCK
(J12 jumper, see Table 3.)
Notes:
1. Xtal is 40 MHz.
2. NC – no connect.
3. NOPOP – do not install.
Table 1. XA-XB Reference Mode of Operation
ICM
Preliminary Rev. 0.2
in Table 2 of the Si5315 data sheet).
NOPOP
install
Xtal
NC
NC
L
Mode
NOPOP
Ext Ref
install
J1
J2
M
Si5315-EVB
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