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AS1520/AS1521

Layout Considerations

The AS1520/AS1521 require proper layout and design procedures for optimum performance.

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Use printed circuit boards; wirewrap boards should not be used.

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Analog and digital traces should be separate and should not run parallel to each other (especially clock traces).

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Digital traces should not run beneath the AS1520/AS1521.

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Use a single-point analog ground at GND, separate from the digital ground (see Figure 36). Connect all other ana-

log grounds and DGND to this star ground point for further noise reduction. No other digital system ground should

be connected to this single-point analog ground. The ground return to the power supply for this ground should be

low impedance and as short as possible for noise-free operation.

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this supply to the single-point analog ground with 0.1µF and 4.7µF bypass capacitors. Bypass capacitors should

be as close to the device as possible for optimum power supply noise-rejection. If the power supply is very noisy, a

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Ω resistor can be connected as a low-pass filter to attenuate supply noise (see Figure 36).

Figure 36. Recommended GND Design

Power

Supplies

Digital

Circuitry

+

+

10

Ω

(Optional)

9

COM

GND

GND

DGND

19

13

GND

20

AS1520/

AS1521

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