AD7147 datasheet(24/73 Pages) AD

24 / 73 page

Data Sheet

AD7147

Rev. D | Page 23 of 72

NOTES

1. SLOW_FILTER_EN, WHICH IS THE NAME OF THE OUTPUT OF COMPARATOR 3, IS SET AND SW1 IS CLOSED WHEN |STAGEx_SF_WORD0 – CDC VALUE|

EXCEEDS THE VALUE PROGRAMMED IN THE SLOW_FILTER_UPDATE_LVL REGISTER PROVIDING PROXIMITY IS NOT SET.

2. PROXIMITY 1 IS SET WHEN |STAGEx_FF_WORD0 – STAGEx_FF_WORD3| EXCEEDS THE VALUE PROGRAMMED IN THE

PROXIMITY_DETECTION_RATE REGISTER.

3. PROXIMITY 2 IS SET WHEN |AVERAGE – AMBIENT| EXCEEDS THE VALUE PROGRAMMED IN THE PROXIMITY_RECAL_LVL REGISTER.

4. DESCRIPTION OF COMPARATOR FUNCTIONS:

COMPARATOR 1: USED TO DETECT WHEN A USER IS APPROACHING OR LEAVING A SENSOR.

COMPARATOR 2: USED TO DETECT WHEN A USER IS HOVERING OVER A SENSOR OR APPROACHING A SENSOR VERY SLOWLY.

ALSO USED TO DETECT IF THE SENSOR AMBIENT LEVEL HAS CHANGED AS A RESULT OF THE USER INTERACTION.

FOR EXAMPLE, HUMIDITY OR DIRT LEFT BEHIND ON SENSOR.

COMPARATOR 3: USED TO ENABLE THE SLOW FILTER UPDATE RATE. THE SLOW FILTER IS UPDATED WHEN SLOW_FILTER_EN IS SET AND

PROXIMITY IS NOT SET.

BANK 3 REGISTERS

SW1

PROXIMITY

SLOW_FILTER_EN

STAGEx_SF_WORD0

STAGEx_SF_WORD1

STAGEx_SF_WORD2

STAGEx_SF_WORD3

STAGEx_SF_WORD4

STAGEx_SF_WORD5

STAGEx_SF_WORD6

STAGEx_SF_WORD7

STAGEx_FF_WORD0

STAGEx_FF_WORD1

STAGEx_FF_WORD2

STAGEx_FF_WORD3

STAGEx_FF_WORD4

STAGEx_FF_WORD5

STAGEx_FF_WORD6

STAGEx_FF_WORD7

ΣWORD(N)

N = 0

COMPARATOR 3

WORD0 – CDC VALUE

SLOW_FILTER_UPDATE_LVL

STAGEx_SF_AMBIENT

BANK 3 REGISTERS

CDC

COMPARATOR 1

|WORD0 – WORD3|

PROXIMITY_DETECTION_RATE

COMPARATOR 2

|AVERAGE – AMBIENT|

PROXIMITY_RECAL_LVL

PROXIMITY 1

PROXIMITY

LP_PROXIMITY_CNT

FP_PROXIMITY_CNT

LP_PROXIMITY_RECAL

FP_PROXIMITY_RECAL

PROXIMITY TIMING

CONTROL LOGIC

AMBIENT

VALUE

STAGEx_SF_WORDx

STAGEx_FF_WORDx

SENSOR

CONTACT

STAGEx_FF_AVG

BANK 3 REGISTERS

Figure 34. AD7147 Proximity-Detection Logic

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