sm840001 Micrel Semiconductor, sm840001 Datasheet - Page 6

• Manufacturer Part Number: sm840001
• Description: 106.25mhz Ultra-low Jitter Clock Synthesizer
• Manufacturer: Micrel Semiconductor

Micrel, Inc.
Power Supply Filtering
The SM840001 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.
March 2010
Figure 2.
6
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 of the
crystal must be considered in order to calculate
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.
or [phone]
M9999-031810-B
Shunt
Cap.
Max.
7pF
SM840001
Drive
Max.
0.1m
W