Datasheet

 2012-2013 Microchip Technology Inc. Advance Information DS40001667C-page 9
MGC3130
2.2.1.3 Approach Detection
Approach Detection is an embedded power-saving
feature of Microchip’s Colibri Suite. It sends MGC3130
to Sleep mode and scans periodically the sensing area
to detect the presence of a human hand.
Utilizing the in-built Self Wake-up mode, Approach
Detection alternates between Sleep and Scan phases.
During the Scan phases, the approach of a human
hand can be detected while very low power is
consumed. For more details, please see
Section 4.2.4.3 “Self Wake-up Mode”.
A detected approach of a user exceeding configured
threshold criteria will alternate the MGC3130 from Self
Wake-up to Processing mode or even the application
host in the overall system.
Within the Approach Detection sequence, the following
scans are performed:
• Approach Scan
: An Approach Scan is performed
during the Scan phase of the MGC3130’s Self
Wake-up mode. Typically, 1 Rx channel is active
but more channels can be activated via GestIC
Library. The time interval (Scan Interval) between
two consecutive Approach Scans is configurable.
For typical applications, the scan cycle is in a
range of 20 ms to 150 ms. During the Approach
Scan, the activated Rx channels are monitored for
signal changes which are caused by, for example,
an approaching human hand and exceeding the
defined threshold. This allows an autonomous
wake-up of the MGC3130 and host applications at
very low-power consumption.
• Calibration Scan
(1)
: The Approach Detection
feature includes the possibility to perform
additional Calibration Scans for the continuous
adaptation of the electrode system to
environmental changes.
A Calibration Scan is performed during the Scan
phase of the MGC3130’s Self Wake-up mode.
Five Rx channels are active to calibrate the
sensor signals. The Calibration Scan is usually
performed in configurable intervals from 2s to
1024s.
To reduce the power consumption, the number of
scans per second can be decreased after a
certain time of non-user activity. Colibri Suite
provides a full user flexibility to configure the
starting Calibration Scans rate (Calibration Start
Scan Interval), non-user activity time-out
(Calibration Transition Time) and the Calibration
Scans rate (Calibration Final Scan Interval) which
will be used afterwards. A typical implementation
uses Calibration Scans every 2s during the first
two minutes, and every 10s afterwards, until an
approach is detected.
The timing sequence of the Approach Detection feature
is illustrated in Figure 2-3.
FIGURE 2-3: APPROACH DETECTION SEQUENCE
Note 1: The Calibration Scan is only needed for
applications using the Position Tracking
feature.
Current
time
Periodic Approach Scans
Calibration
Scan
Periodic Approach Scans
Calibration
Scan
Periodic Approach Scans
Calibration
Scan
Periodic Approach Scans
Scan Interval
20ms-150ms
Calibration Start Scan Interval
2s-10s
I
sleep
= 9µA
I
5CHSCAN
= 20mA
I
5CHSCAN
: Scan Phase with 5 active RX channels: Calibration Scan
I
sleep
: Sleep Phase
Calibration Final Scan Interval
2s-1024s
Calibration Transition Time (Non-user activity timeout)
2s-255s
Processing
Mode
Idle Timeout
5s-1024s
Self Wake-up mode