CAP1114 datasheet(49/102 Pages) MICROCHIP

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Multiple Channel Capacitive Touch Sensor and LED Driver

Datasheet

SMSC CAP1114

Revision 1.1 (02-04-11)

DATASHEET

The Queue Control Register determines the number of consecutive samples for which a single sensor

output is above the Sensor Threshold before a touch is detected. This is also used to determine the

number of consecutive samples used to detect a button release. The queue applies independently to

all channels.

Bits 2 - 0 - QUEUE_B[2:0] - The number of consecutive samples necessary to detect a touch. Default

is 3 consecutive samples. See Table 6.15.

6.13

Data Sensitivity Registers

The Data Sensitivity Register controls the sensitivity of all button channels.

Bits 6- 4 DELTA_SENSE[2:0] - Controls the sensitivity of a touch detection. The sensitivity settings act

to scale the relative delta count value higher or lower based on the system parameters. A setting of

000b is the most sensitive while a setting of 111b is the least sensitive (see Table 6.17). At the more

sensitive settings, touches are detected for a smaller delta C corresponding to a “lighter” touch. These

settings are more sensitive to noise and a noisy environment may flag more false touches than 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).

Table 6.15 QUEUE_B Bit Decode

QUEUE_B[2:0]

NUMBER OF CONSECUTIVE

READINGS > THRESHOLD

3 (default)

Table 6.16 Data Sensitivity Register

ADDR

R/W

DEFAULT

1Fh

R/W

Data Sensitivity

DELTA_SENSE[2:0]

BASE_SHIFT[3:0]

2Fh

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