CAP1208 datasheet(34/67 Pages) MICROCHIP

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8-Channel Capacitive Touch Sensor

Datasheet

DS00001570B-page 34

 2014 Microchip Technology Inc.

corresponding to a “lighter” touch. These settings are more sensitive to noise, however, and a noisy

environment may flag more false touches with higher sensitivity levels.

APPLICATION NOTE: A value of 128x is the most sensitive setting available. At the most sensitive settings, the

MSB of the Delta Count register represents 64 out of ~25,000 which corresponds to a touch

of approximately 0.25% of the base capacitance (or a

ΔC of 25fF from a 10pF base

capacitance). Conversely, a value of 1x is the least sensitive setting available. At these

settings, the MSB of the Delta Count register corresponds to a delta count of 8192 counts

out of ~25,000 which corresponds to a touch of approximately 33% of the base capacitance

(or a

ΔC of 3.33pF from a 10pF base capacitance).

Bits 3 - 0 - BASE_SHIFT[3:0] - Controls the scaling and data presentation of the Base Count registers.

The higher the value of these bits, the larger the range and the lower the resolution of the data

presented. The scale factor represents the multiplier to the bit-weighting presented in these register

descriptions.

APPLICATION NOTE: The BASE_SHIFT[3:0] bits normally do not need to be updated. These settings will not affect

touch detection or sensitivity. These bits are sometimes helpful in analyzing the Cap Sensing

board performance and stability.

Table 5.7 DELTA_SENSE Bit Decode

DELTA_SENSE[2:0]

SENSITIVITY MULTIPLIER

210

128x (most sensitive)

001

64x

32x (default)

011

16x

100

101

110

1x - (least sensitive)

Table 5.8 BASE_SHIFT Bit Decode

BASE_SHIFT[3:0]

DATA SCALING

FACTOR

16x

32x

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