CAP1028 datasheet(29/71 Pages) SMSC

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8 Channel Capacitive Touch Sensor with 2 LED Drivers

Datasheet

SMSC CAP1028

Revision 1.1 (08-05-09)

DATASHEET

1. Fully Active - The device is fully active. It is monitoring all active Capacitive Sensor channels and

driving all LED channels as defined.

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

(as determined by the Standby Channel register - default none). 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.

3. Deep Sleep - The device is in its lowest power state. It is not monitoring any Capacitive Sensor

channels. It can be awakened by SMBus or SPI communications targeting the device (which will

cause the DSLEEP bit to be automatically cleared).

If the device is not communicating via the 4-wire SPI bus, then during this state of operation, if the

WAKE/SPI_MOSI pin is driven high by an external source, the device will clear the DSLEEP bit

and return to Fully Active.

APPLICATION NOTE: The Deep Sleep state does not change LED drive behavior so it is It is the user’s

responsibility to ensure that the LEDs are driven to the desired state prior to entering Deep

Sleep. This is best achieved by unlinking the LEDs from the sensors and driving the LEDs

to the desired state using the LED Output Control register.

APPLICATION NOTE: If the CAP1028 is configured to communicate using the BC-Link protocol, the device does

not support Deep Sleep.

4.2

RESET Pin

The RESET pin is an active high reset that is driven from an external source. While it is asserted high,

all the internal blocks will be held in reset including the communications protocol used. No Capacative

Touch sensors will be sampled and the LEDs will not be driven.

All configuration settings will be reset to default states (thus waking the device from Deep Sleep) and

all readings will be cleared. Once the RESET pin is pulled low, the CAP1028 will begin operation as

if a power-on-reset had occurred.

4.3

WAKE/SPI_MOSI Pin Operation

When the CAP1028 is placed in Standby, and is not communicating using the 4-wire SPI protocol,it

will assert the WAKE/SPI_MOSI pin when a touch is detected on one of its sampled sensors. The pin

will remain asserted until the INT bit has been cleared and then it will be de-asserted.

When the CAP1028 is placed in Deep Sleep and it is not commuicating using the 4-wire SPI protocol,

the WAKE/SPI_MOSI pin is monitored by the device as an input. If the WAKE/SPI_MOSI pin is driven

high by an external source, the CAP1028 will clear the DSLEEP bit.

When the device is placed in Deep Sleep, this pin is a High-Z input and must have a pull-down resistor

to GND for proper operation.

4.4

LED Drivers

The CAP1028 contains two (2) LED Drivers. Each LED driver can be configured to operate in one of

the following modes with either push-pull or open drain drive. Additionally, each LED driver can be

linked to the respective Capacitive Touch sensor input.

1. Direct - The LED is configured to be on or off when the corresponding input stimulus is on or off

(or inverted). The brightness of the LED can be programmed from full off to full on (default).

Additionally, the LED contains controls to individually configure ramping on, off, and turn-off delay.

2. Pulse 1 - The LED is configured to fade ON-OFF-ON a programmable number of times with

programmable rate and min / max brightness. This behavior may be actuated when a press is

detected, or when a release is detected.

CAP1028 Datasheet(PDF) 29 Page - SMSC Corporation

CAP1028 Datasheet(HTML) 29 Page - SMSC Corporation

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