MGC3140 datasheet(27/49 Pages) MICROCHIP

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•

I2C Start bit detection

•

On MCLR Reset

The Deep Sleep mode can be enabled by GestIC Library messages.

6.4.3

Wake-up-on-Approach Mode

The Wake-up-on-Approach mode is a low power mode allowing an autonomous wake-up of the

MGC3140 and application host. In this mode, the MGC3140 is automatically and periodically alternating

between Deep Sleep and scan phases.

During the approach scan phase, the sensor will be able to detect an approach of the human hand and

change to Processing mode accordingly.

The MGC3140’s fast wake-up, typically below 1 ms, allows the performance of scans in very efficient

periods and to maximize the Sleep phase.

Additionally, the sensor will perform periodic AFA scans in which the sensor will scan through all available

Tx frequencies and select an optimal frequency depending on the signals’ noise level.

The periodic wake-up sequence is triggered by a programmable wake-up timer running at the low-speed

Oscillator 32 kHz frequency. The repetition rate of the scan can be adjusted via the host, affecting the

sensitivity and current consumption during Wake-up-on-Approach.

The MGC3140 enters the Self Wake-up mode by a GestIC Library message or by a non-activity time-out.

Non-activity means no user detection within the sensing area.

The MGC3140 will resume from Self Wake-up on one of the following events:

•

Detection of a human hand approaching the sensor

•

I2C Start bit detection

•

On MCLR or WDTR

6.4.4

Transmit Signal Generation

The Tx signal generation block provides five bandwidth limited square wave signals for the transmit

electrode. The five Tx signals are combined through a resistive network to provide a single Tx signal to

the Tx electrode. This provides slew control to the rising and falling Tx signal edges in order to reduce

radiated emissions. Frequency hopping automatically adjusts the Tx carrier frequency choosing one of

the five transmit frequencies, depending on the environmental noise conditions. GestIC Library

automatically selects the lowest noise working frequency in case the sensor signal is compromised.

Frequencies can be enabled/disabled via the GestIC Library.

6.4.5

Receive (Rx) Channels

There are five identical Rx channels that can be used for five respective receive electrodes. Four receive

electrodes are required for Position Tracking and Gesture Recognition. A fifth electrode can be used for

touch detection and for approach detection in Wake-up on Approach mode. Every Rx input pin is

connected to its own dedicated ADC. The Rx input signal is sampled at a sampling rate equal to double

the Tx frequency, providing a high and low ADC sample.

The electrodes can be connected in any order to the external electrodes. The channel assignment is then

done in a parameterization step in Aurea GUI or alliteratively using I2C commands.

MGC3140

Functional Description

DS40002037A-page 27

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