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AS1528/AS1529

Data Sheet - A p p l i c a t i o n I n f o r m a t i o n

Layout and Grounding Considerations

The AS1528/AS1529 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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Separate analog and digital traces from each other. Analog and digital traces should not run parallel to each other

(especially clock traces).

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Digital traces should not run beneath the AS1528/AS1529.

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Use a single-point analog ground at GND, separate from the digital ground (see Figure 29). 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 (see Figure 29). The bypass

capacitors should be placed as close to the device as possible for optimum power supply noise-rejection. If the

power supply is very noisy, a 10

Ω resistor can be connected as a low-pass filter to attenuate supply noise

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Power components such as the inductor, converter IC, filter capacitors, and output diode should be placed as close

together as possible, and their traces should be kept short, direct, and wide.

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Keep the voltage feedback network very close to the device, within 5mm (0.2”) of the pin.

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Keep noisy traces, such as those from the pin LX, away from the voltage feedback network and guarded from

them using grounded copper traces.

Figure 29. Recommended Ground Design

AS1528/

AS1529

Power

Supplies

Digital

Circuitry

0.1µF

GND

+5 or +3V

1

4

GND

+5 or +3V

+5 or +3V

DGND

GND

5

Ω

(Optional)