AD7148

Rev. 0 | Page 31 of 56

PCB DESIGN GUIDELINES

CAPACITIVE SENSOR BOARD MECHANICAL SPECIFICATIONS

Table 16.

Parameter

Symbol

Min

Typ

Max

Unit

Distance from Edge of Any Sensor to Edge of Grounded Metal Object

0.1

mm

Distance Between Sensor Edges1

0

mm

Distance Between Bottom of Sensor Board and Controller Board or Grounded

Metal Casing2

1.0

mm

Adjacent sensors, with 0 minimum space between them, are implemented differentially.

the controller board to the sensors. Address potential EMI coupling issues by placing a grounded metal shield between the capacitive sensor board and the main

controller board, as shown in Figure 43.

SLIDER

BUTTONS

CAPACITIVE SENSOR

PRINTED CIRCUIT

8-WAY

SWITCH

METAL OBJECT

Figure 41. Capacitive Sensor Board Mechanicals Top View

CONTROLLER PRINTED CIRCUIT BOARD OR METAL CASING

CAPACITIVE SENSOR BOARD

Figure 42. Capacitive Sensor Board Mechanicals Side View

CAPACITIVE SENSOR BOARD

CONTROLLER PRINTED CIRCUIT BOARD OR METAL CASING

GROUNDED METAL SHIELD

Figure 43. Capacitive Sensor Board with Grounded Shield

CHIP SCALE PACKAGES

The lands on the chip scale package (CP-16-13) are rectangular.

The printed circuit board pad for this package should be 0.1 mm

longer than the package land length and 0.05 mm wider than

the package land width. Center the land on the pad to maximize

the solder joint size.

The bottom of the chip scale package has a central thermal pad.

The thermal pad on the printed circuit board should be at least

as large as this exposed pad. To avoid shorting, provide a clearance

of at least 0.25 mm between the thermal pad and the inner edges

of the land pattern on the printed circuit board.

Thermal vias can 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 a 1.2 mm

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.

Connect the printed circuit board thermal pad to GND.