CAP1106 datasheet(36/48 Pages) MICROCHIP

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CAP1106

DS00001624B-page 36

 2015 Microchip Technology Inc.

Bits 2 - 0 - STBY_SENSE[2:0] - Controls the sensitivity for sensor inputs that are active in Standby. The sensitivity set-

tings 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. 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 however and a noisy envi-

ronment may flag more false touches than higher sensitivity levels.

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

6.23

Standby Threshold Register

The Standby Threshold register stores the delta threshold that is used to determine if a touch has been detected. When

a touch occurs, the input signal of the corresponding sensor pad changes due to the capacitance associated with a

touch. If the sensor input change exceeds the threshold settings, a touch is detected.

6.24

Sensor Input Base Count Registers

TABLE 6-41:

STBY_SENSE BIT DECODE

STBY_SENSE[2:0]

Sensitivity Multiplier

210

128x (most sensitive)

001

64x

32x (default)

011

16x

100

101

110

1x - (least sensitive)

TABLE 6-42:

STANDBY THRESHOLD REGISTER

ADDR

R/W

B5B4

B3B2

B1B0

Default

43h

R/W

Standby Thresh-

old

-64

40h

TABLE 6-43:

SENSOR INPUT BASE COUNT REGISTERS

ADDR

R/W

B5B4

B3B2

B1B0

Default

50h

Sensor Input 1

Base Count

128

C8h

51h

Sensor Input 2

Base Count

128

C8h

52h

Sensor Input 3

Base Count

128

C8h

53h

Sensor Input 4

Base Count

128

C8h

54h

Sensor Input 5

Base Count

128

C8h

55h

Sensor Input 6

Base Count

128

C8h

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