MGC3140 datasheet(16/49 Pages) MICROCHIP

16 / 49 page

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An Approach scan is performed during the scan phase of the device’s Self Wake-up mode.

Typically, one Rx channel is active but more channels can be activated via the 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 MGC3140 and host applications at very low-power consumption.

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AFA Scan

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During Wake-up-on-Approach, periodic Automatic Frequency Adaptation (AFA) scans are

performed. During this scan, the environmental noise is measured and a new Tx frequency

will be selected from the five preset frequencies available, if necessary. The AFA scan is

usually performed in configurable intervals from 120s to 600s (120s typical). The timing

sequence of the Approach Detection feature is illustrated below:

Figure 4-7. Approach Detection Sequence

C u rre n t

tim e

Perio d ic A p p ro ach Scan s

A FA S ca n

Perio d ic A p pro ach Scan s

A FA S c a n

Period ic A p p ro ach Scans

A FA S c an

Perio d ic A p p ro ach Scan s

20 m s-150 m s

2s-10 s

ISLEEP = 62 µA

I5CHSCA N = 29 m A

I5CHSCA N

: Scan Phase w ith 5 active RX channels: Calibration Scan

ISLEEP

Sleep Phase

120 s -600 s

N on -user ac tivity tim eout

2s- 255 s

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