sm840001 Micrel Semiconductor, sm840001 Datasheet - Page 7

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

Micrel, Inc.
Total capacitance seen by crystal = CL =
Board Layout
March 2010
(Ct1 + Cb1 + Cd1)
1
+
1
(Ct2 + Cb2 + Cd2)
1
7
Example:
CL = 18pF, Cb = 2pF, Cd = 4pF
Trim Cap = Ct = 2 (18pF) - (2pF +4pF) = 30pF
The SM843022 has been characterized with 25MHz,
18pF parallel resonant crystal. The trim capacitors Ct1
and Ct2 were optimized to minimize the ppm error.
To minimize the board capacitance, a short trace from
pin to crystal footprint without vias is desirable. It is
preferable to have ground shielding or distance between
the crystal traces and noisy signals on the board.
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M9999-031810-B
SM840001