sm840004-11 Micrel Semiconductor, sm840004-11 Datasheet - Page 8

• Manufacturer Part Number: sm840004-11
• Description: 62.5/125mhz Gigabit Ethernet, 4 Output, Ultra-low Jitter Clock Synthesizer
• Manufacturer: Micrel Semiconductor

Micrel, Inc.
Power Supply Filtering
The SM840004-11 provides separate power supply pins to
isolate any high switching noise from outputs to internal
core blocks. VDD and VDDA should be individually
connected to the power plane through vias. Bypass
capacitors should be used for each pin. Figure 2,
illustrates how the power supply filter for 3.3V and 2.5V is
configured.
July 2010
Figure 2. Power Supply Filter
8
Crystal Loading
Crystal Recommendations
This device requires a parallel resonance crystal.
Substituting a series resonance crystal will cause this
device to operate at the wrong frequency and violate the
ppm specifications.
To achieve low ppm error, the total capacitance the crystal
will see must be considered to calculate the appropriate
capacitive loading (CL).
Load Capacitance at each side: Trim Capacitance = Ct =
(2*CL-(Cb + Cd))
CL: Crystal load capacitance. Defined by manufacturer
Ct: External trim capacitors. (Trimmed CL Load
capacitance to get the right ppm)
Cb: Board capacitance (vias, traces, etc.)
Cd: Internal capacitance of the device (lead frame, bond
wires, pin, etc.)
Crystal Input Interface
Equivalent Series
Resistance (ESR)
Max.
50Ω
[e-mail]
Cut
AT
Load
18pF
Cap.
Shunt
Max.
Cap.
7pF
or [phone]
M9999-070110-A
SM840004-11
0.1mW
Drive
Max.