CAP1208 datasheet(23/67 Pages) MICROCHIP

23 / 67 page

8-Channel Capacitive Touch Sensor

Datasheet

 2014 Microchip Technology Inc.

DS00001570B-page 23

Note 4.1

Delayed recalibration only works when the delta count is above the active sensor input

threshold. If enabled, it is invoked when a sensor pad touch is held longer than the

MAX_DUR bit settings.

Note 4.2

For the power button, which requires that the button be held longer than a regular button,

the time specified by the MAX_DUR[3:0] bits is added to the time required to trigger the

qualifying event. This will prevent the power button from being recalibrated during the time

it is supposed to be held.

4.5

Power Button

The CAP1208 has a “power button” feature. In general, buttons are set for quick response to a touch,

especially when buttons are used for number keypads. However, there are cases where a quick

response is not desired, such as when accidentally brushing the power button causes a device to turn

off or on unexpectedly.

The power button feature allows a sensor input to be designated as the “power button” (see Section

5.26, "Power Button Register"). The power button is configured so that a touch must be held on the

button for a designated period of time before an interrupt is generated; different times can be selected

for the Standby and the Active states (see Section 5.27, "Power Button Configuration Register"). The

feature can also be enabled / disabled for both states separately.

APPLICATION NOTE: For the power button feature to work in the Standby and/or Active states, the sensor input

must be enabled in the applicable state.

After the designated power button has been held for the designated time, an interrupt is generated

and the PWR bit is set in the General Status Register (see Section 5.2, "Status Registers").

4.6

Multiple Touch Pattern Detection

The multiple touch pattern (MTP) detection circuitry can be used to detect lid closure or other similar

events. An event can be flagged based on either a minimum number of sensor inputs or on specific

sensor inputs simultaneously exceeding an MTP threshold or having their Noise Flag Status Register

bits set. An interrupt can also be generated. During an MTP event, all touches are blocked (see

Section 5.15, "Multiple Touch Pattern Configuration Register").

4.7

Noise Controls

4.7.1

Low Frequency Noise Detection

Each sensor input has a low frequency noise detector that will sense if low frequency noise is injected

onto the input with sufficient power to corrupt the readings. By default, if this occurs, the device will

reject the corrupted sample (see DIS_ANA_NOISE bit in Section 5.6.1, "Configuration - 20h") and the

corresponding bit is set to a logic ‘1’ in the Noise Flag Status register (see SHOW_RF_NOISE bit in

Section 5.6.2, "Configuration 2 - 44h").

4.7.2

RF Noise Detection

Each sensor input contains an integrated RF noise detector. This block will detect injected RF noise

on the CS pin. The detector threshold is dependent upon the noise frequency. By default, if RF noise

is detected on a CS line, that sample is removed and not compared against the threshold (see

DIS_RF_NOISE bit in Section 5.6.2, "Configuration 2 - 44h").

4.7.3

Noise Status and Configuration

The Noise Flag Status (see Section 5.3, "Noise Flag Status Registers") bits can be used to indicate

RF and/or other noise. If the SHOW_RF_NOISE bit in the Configuration Register (see Section 5.6,

CAP1208 датащи(PDF) 23 Page - Microchip Technology

CAP1208 датащи(HTML) 23 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67

датащи скачать

ссылки URL