CAP1026 datasheet(48/70 Pages) SMSC

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6 Channel Capacitive Touch Sensor with 2 LED Drivers

Datasheet

Revision 1.1 (08-05-09)

SMSC CAP1026

DATASHEET

The Sensor Threshold registers store 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 changes due to the

capacitance associated with a touch. If the sensor input change exceeds the threshold settings, then

a touch is detected.

When the BUT_LD_TH bit is set (see Section 5.15 - bit 7), writing data to the Sensor 1 Threshold

5.17

Sensor Noise Threshold Registers

The Sensor Noise Threshold registers control the value of a secondary internal threshold to detect

noise and improve the automatic recalibration routine. If a Capacitive Touch Sensor output exceeds

the Sensor Noise Threshold but does not exceed the sensor threshold, then it is determined to be

caused by a noise spike. That sample is not used by the automatic re-calibration routine.

The Sensor Noise Threshold is proportional to the programmed threshold as shown in Table 5.28.

5.17.1

Sensor Noise Threshold 1 Register

The Sensor Noise Threshold 1 register controls the noise threshold for Capacitive Touch Sensors 1-4.

Bits 7-6 - CS4_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 4.

Bits 5-4 - CS3_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 3.

Bits 3-2 - CS2_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 2.

Bits 1-0 - CS1_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 1.

5.17.2

Sensor Noise Threshold 2 Register

The Sensor Noise Threshold 2 register controls the noise threshold for Capacitive Touch Sensors 5 - 6.

Bits 3-2 - CS6_BN_TH[1:0] - Controls the noise threshold for Capacitive Touch Sensor 6.

Table 5.27 Sensor Noise Threshold Registers

ADDR

R/W

DEFAULT

38h

R/W

Sensor Noise

Threshold 1

CS4_BN_TH

[1:0]

CS3_BN_TH

[1:0]

CS2_BN_TH

[1:0]

CS1_BN_TH

[1:0]

55h

39h

R/W

Sensor Noise

Threshold 2

010

CS6_BN_TH

[1:0]

CS5_BN_TH

[1:0]

55h

Table 5.28 CSx_BN_TH Bit Decode

CSX_BN_TH[1:0]

THRESHOLD DIVIDE SETTING

25%

37.5% (default)

50%

62.5%

CAP1026 Datasheet(PDF) 48 Page - SMSC Corporation

CAP1026 Datasheet(HTML) 48 Page - SMSC Corporation

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