AD7873 Datasheet, PDF (23/28 Pages) Analog Devices – Touch Screen Digitizer

GROUNDING AND LAYOUT
For information on grounding and layout considerations for the
AD7873, refer to Application Note AN-577, Layout and
Grounding Recommendations for Touch Screen Digitizers.
PCB DESIGN GUIDELINES FOR
CHIP SCALE PACKAGE
The lands on the chip scale package (CP-32), are rectangular.
The printed circuit board pad for these should be 0.1 mm
longer than the package land length and 0.05 mm wider than
the package land width. The land should be centered on the pad.
This will ensure that the solder joint size is maximized.
The bottom of the chip scale package has a central thermal pad.
The thermal pad on the printed circuit board should be at least
AD7873
as large as this exposed pad. On the printed circuit board, there
should be a clearance of at least 0.25 mm between the thermal
pad and the inner edges of the pad pattern. This ensures that
shorting is avoided.
Thermal vias may be used on the printed circuit board thermal
pad to improve thermal performance of the package. If vias are
used, they should be incorporated in the thermal pad at 1.2mm
pitch grid. The via diameter should be between 0.3 mm and
0.33 mm and the via barrel should be plated with 1 oz. copper
to plug the via.
The user should connect the printed circuit board thermal pad
to GND.
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