IQS228AS datasheet(4/30 Pages) ETC2

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IQ Switch

® ProxSense® Series

IQS228AS Datasheet

Page 4 of 30

Revision 1.05

October 2015

Overview

1.1 Device

The

IQS228AS

single

channel

capacitive proximity and touch device which

employs an internal voltage regulator and

reference capacitor (Cs).

The IQS228AS device has a dedicated

pin(s) for the connection of a sense

electrode(s) (Cx) and output pin(s) for

proximity and touch events on OUT. The

polarity

the

output

pins

can

configured.

1-wire

open

drain

data

streaming protocol OR I

2C interface is

implemented for debugging purposes.

Special device configuration can be done

by setting one time programmable (OTP)

options.

The

device

automatically

tracks

slow

varying environmental changes via various

signal processing algorithms and has an

Automatic

Tuning

Implementation

(ATI)

algorithm to calibrate the device to the

sense electrode.

DYCAL™ (Dynamic Calibration) is a

special form of hysteresis that can track

slow varying environmental change even

while the sensor is in a touch state. This is

ideal for portable applications.

The charge transfer method of capacitive

sensing is employed on the IQS228AS.

(The charge transfer principle is thoroughly

described in the application note:

“AZD004

Azoteq Capacitive Sensing”.)

1.2

Operation

The device has been designed to be used

in applications where proximity is required

and touch conditions can prevail for an

extended period of time which may result in

uncompensated

drift

conventional

capacitive sensors.

A low threshold is used to detect the

proximity of an object, with a higher

threshold for touch detection.

Dynamic Calibration is performed when a

TOUCH condition is detected for longer

than tDYCAL. The hysteresis algorithm will

now check for the release condition of the

touch, while still tracking environmental

changes

1.3 Applicability

All specifications, except where specifically

mentioned

otherwise,

provided

this

datasheet are applicable to the following

ranges:

 Temperature:-40C to +85C

 Supply voltage (V

DDHI): 1.8V to 3.6V

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