CAP1128 datasheet(24/75 Pages) MICROCHIP

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CAP1128

DS00001622B-page 24

 2015 Microchip Technology Inc.

5.1

Power States

The CAP1128 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 and driving all LED chan-

nels as defined.

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 and not

driving any LEDs. All LEDs will be driven to their programmed non-actuated state and no PWM operations will

be done. 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 communi-

cations have stopped.

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: In the Deep Sleep state, the LED output will be either high or low and will not be PWM’d at

the min or max duty cycle.

5.2

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 capacitive touch sensor inputs will be sam-

pled and the LEDs will not be driven. All configuration settings will be reset to default states and all readings will be

cleared.

The device will be held in Deep Sleep that can only be removed by driving the RESET pin low. This will cause the

RESET status bit to be set to a logic ‘1’ and generate an interrupt.

5.3

WAKE/SPI_MOSI Pin Operation

The WAKE / SPI_MOSI pin is a multi-function pin depending on device operation. When the device is configured to com-

municate using the 4-wire SPI bus, this pin is an input.

However, when the CAP1128 is placed in Standby and is not communicating using the 4-wire SPI protocol, the WAKE

pin is an active high output. In this condition, the device will assert the WAKE/SPI_MOSI pin when a touch is detected

on one of its sampled sensor inputs. The pin will remain asserted until the INT bit has been cleared and then it will be

de-asserted.

When the CAP1128 is placed in Deep Sleep and it is not communicating 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

CAP1128will clear the DSLEEP bit causing the device to return to Fully Active.

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.

5.4

LED Drivers

The CAP1128 contains two (2) LED drivers. Each LED driver can be linked to its respective capacitive touch sensor

input or it can be controlled by the host. Each LED driver can be configured to operate in one of the following modes

with either push-pull or open drain drive.

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.

Pulse 1 - The LED is configured to “Pulse” (transition ON-OFF-ON) a programmable number of times with pro-

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

release is detected.

Pulse 2 - The LED is configured to “Pulse” while actuated and then “Pulse” a programmable number of times with

programmable rate and min / max brightness when the sensor pad is released.

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