SI5350A-B Datasheet, PDF (14/29 Pages) Silicon Laboratories – FACTORY-PROGRAMMABLE ANY-FREQUENCY CMOS CLOCK GENERATOR

Si5350A-B
4.4. Design Considerations
The Si5350A is a self-contained clock generator that requires very few external components. The following general
guidelines are recommended to ensure optimum performance.
4.4.1. Power Supply Decoupling/Filtering
The Si5350A has built-in power supply filtering circuitry to help keep the number of external components to a
minimum. All that is recommended is one 0.1 to 1.0 µF decoupling capacitor per power supply pin. This capacitor
should be mounted as close to the VDD and VDDO pins as possible without using vias.
4.4.2. Power Supply Sequencing
The VDD and VDDOx (i.e., VDDO0, VDDO1, VDDO2, VDDO3) power supply pins have been separated to allow
flexibility in output signal levels. Power supply sequencing for VDD and VDDOx requires that all VDDOx be
powered up either before or at the same time as VDD. Unused VDDOx pins should be tied to VDD.
4.4.3. External Crystal
The external crystal should be mounted as close to the pins as possible using short PCB traces. The XA and XB
traces should be kept away from other high-speed signal traces. See “AN551: Crystal Selection Guide” for more
details.
4.4.4. External Crystal Load Capacitors
The Si5350A provides the option of using internal and external crystal load capacitors. If external load capacitors
are used, they should be placed as close to the XA/XB pads as possible. See “AN551: Crystal Selection Guide” for
more details.
4.4.5. Unused Pins
Unused control pins (P0–P4) should be tied to GND.
Unused output pins (CLK0–CLK7) should be left floating.
4.4.6. Trace Characteristics
The Si5350A features various output drive strength settings. It is recommended to configure the trace
characteristics as shown in Figure 10 when the default high output drive setting is used.
Z_O = 50 ohms
CLK
R = 0 ohms
(Optional resistor for
EMI management)
Figure 10. Recommended Trace Characteristics with Default Drive Strength Setting
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Rev. 1.0