Si5355-EVB Silicon Laboratories Inc, Si5355-EVB Datasheet - Page 9

• Manufacturer Part Number: Si5355-EVB
• Description: Clock & Timer Development Tools Si5355 custom clk eval board
• Manufacturer: Silicon Laboratories Inc

Specifications of Si5355-EVB

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3. Functional Description
3.1. Input Configuration
The Si5355 input can be driven from either an external crystal or a reference clock. Reference selection is made
when the device configuration is specified using the ClockBuilder™ web-based utility available at
ClockBuilder. If the crystal input option is used, the Si5355 operates as a free-running clock generator. In this mode
of operation the device requires a low-cost 25 or 27 MHz fundamental mode crystal connected across XA and XB
as shown in Figure 2. Given the Si5355’s frequency flexibility, the same 25 or 27 MHz crystal can be reused to
generate any combination of output frequencies. Custom frequency crystals are not required. The Si5355
integrates the crystal load capacitors on-chip to reduce external component count. The crystal should be placed
very close to the device to minimize stray capacitance. To ensure stable oscillation, the recommended crystal
specifications provided in Table 5 on page 7 must be followed. See AN360 for additional details regarding crystal
recommendations.
For synchronous timing applications, the Si5355 can lock to a 5 to 200 MHz CMOS reference clock. A typical
interface circuit is shown in Figure 3. A series termination resistor matching the driver’s output impedance to the
impedance of the transmission line is recommended to reduce reflections.
Figure 3. Interfacing CMOS Reference Clocks to the Si5355
Figure 2. Connecting an XTAL to the Si5355
Figure 1. Si5355 Functional Block Diagram
Rs
XTAL
50
Rev. 0.3
Si5355
XA
XB
Si5355
CLKIN
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Si5355
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