AS1524/AS1525
Datasheet - Application Information
Layout and Grounding Considerations
The AS1524/AS1525 require proper layout and design procedures for optimum performance.
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Use printed circuit boards; wirewrap boards should not be used.
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 AS1524/AS1525.
Use a single-point analog ground at GND, separate from the digital ground (see Figure 30). 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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High-frequency noise in the VDD power supply may affect the AS1524/AS1525 high-speed comparator. Bypass
this supply to the single-point analog ground with 0.1µF and 4.7µF bypass capacitors (see Figure 30). 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 10Ω resistor can be connected as a low-pass filter to attenuate supply noise
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.
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 30. Recommended Ground Design
+5 or +3V
+5 or +3V
DGND
Digital
Circuitry
GND
GND
Power
Supplies
4
GND
AS1524/
AS1525
0.1µF
5Ω
(Optional)
1
+5 or +3V
VDD
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