SM532 Datasheet, PDF (13/14 Pages) List of Unclassifed Manufacturers – Low EMI Spectrum Spread Clock

+/+
YJGP VKOKPI KU ETKVKECN
Approved Product
SM532
Low EMI Sprectum Spread Clock
Figure 10 shows the internal oscillator equivalent circuit for the SM532.
.
250 K
1
Xin
1
2
.
3 pF
2
Xout
5 pF
.
Figure 10. Internal Oscillator Equivalent Circuit
PCB Layout Example
The SM532 Spectrum Spread Clock is a PLL type hybrid circuit. This means that is contains both digital and
analog circuits on the same die. The Phase Detector, Loop Filter and VCO are analog circuits that must operate
in a very low noise environment for best performance. There are several ways to keep this noise to a minimum,
such as bypass capacitors on all power pins and separating the analog and digital power and ground planes. The
figure below uses the first approach of placing bypass capacitors as close to every power pin as possible. In
addition, all ground pins should be connected directly to the ground plane with little or no trace length. Note also
that only the power and ground circuits of the SM532 have been shown. Other circuits such as the Loop Filter
components must be located as close to the Loop Filter pin as possible, for best performance.
VSS
VSS
Pin 1
0.1 uf.
22 uf.
10 ohm VCC
0.1 uf.
VSS
VSS
VSS
0.1 uf.
VSS
Figure 11. SM532 Single Power Plane PCB Layout
International Microcircuits,Inc.
525 Los Coches St., Milpitas, 95035 408-263-6300, FAX [phone]
http:/www.imicorp.com
8/31/98
Rev. 1.4
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