CAP1106 datasheet(15/48 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS00001624B-page 15

CAP1106

5.1

Power States

The CAP1106 has three operating states depending on the status of the STBY and DSLEEP bits. When the device tran-

sitions between power states, previously detected touches (for inactive channels) are cleared and the status bits reset.

Fully Active - The device is fully active. It is monitoring all active capacitive sensor inputs.

Standby - The device is in a lower power state. It will measure a programmable number of channels using the

Standby Configuration controls (see Section 6.20 through Section 6.22). Interrupts will still be generated based

on the active channels. The device will still respond to communications normally and can be returned to the Fully

Active state of operation by clearing the STBY bit.

Deep Sleep - The device is in its lowest power state. It is not monitoring any capacitive sensor inputs. While in

Deep Sleep, the device can be awakened by SMBus or SPI communications targeting the device. This will not

cause the DSLEEP to be cleared so the device will return to Deep Sleep once all communications have stopped.

5.2

Capacitive Touch Sensing

The CAP1106 contains six (6) independent capacitive touch sensor inputs. Each sensor input has dynamic range to

detect a change of capacitance due to a touch. Additionally, each sensor input can be configured to be automatically

and routinely re-calibrated.

5.2.1

SENSING CYCLE

Each capacitive touch sensor input has controls to be activated and included in the sensing cycle. When the device is

active, it automatically initiates a sensing cycle and repeats the cycle every time it finishes. The cycle polls through each

active sensor input starting with CS1 and extending through CS6. As each capacitive touch sensor input is polled, its

measurement is compared against a baseline “Not Touched” measurement. If the delta measurement is large enough,

a touch is detected and an interrupt is generated.

The sensing cycle time is programmable (see Section 6.10, "Averaging and Sampling Configuration Register").

5.2.2

RECALIBRATING SENSOR INPUTS

There are various options for recalibrating the capacitive touch sensor inputs. Recalibration re-sets the Base Count Reg-

isters (Section 6.24, "Sensor Input Base Count Registers") which contain the “not touched” values used for touch detec-

tion comparisons.

APPLICATION NOTE: The device will recalibrate all sensor inputs that were disabled when it transitions from

Standby. Likewise, the device will recalibrate all sensor inputs when waking out of Deep

Sleep.

5.2.2.1

Manual Recalibration

The Calibration Activate Registers (Section 6.11, "Calibration Activate Register") force recalibration of selected sensor

inputs. When a bit is set, the corresponding capacitive touch sensor input will be recalibrated (both analog and digital).

The bit is automatically cleared once the recalibration routine has finished.

5.2.2.2

Automatic Recalibration

Each sensor input is regularly recalibrated at a programmable rate (see Section 6.17, "Recalibration Configuration Reg-

ister"). By default, the recalibration routine stores the average 64 previous measurements and periodically updates the

base “not touched” setting for the capacitive touch sensor input.

Note:

During this recalibration routine, the sensor inputs will not detect a press for up to 200ms and the Sensor

Base Count Register values will be invalid. In addition, any press on the corresponding sensor pads will

invalidate the recalibration.

Note:

Automatic recalibration only works when the delta count is below the active sensor input threshold. It is dis-

abled when a touch is detected.

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