IQS243 Datasheet
®
IQ Switch - ProxSense Series
3 Channel Capacitive Sensor with I
2
C
TM
compatible interface and Compensation for
Sensitivity Reducing Objects
Unparalleled Features
Sub 3uA current consumption
Automatic tuning for optimal operation in various environments
The IQS243 ProxSense
®
IC is a fully integrated 3 channel capacitive contact and proximity
sensor with market leading sensitivity and automatic tuning to the sense antenna. The IQS243
provides a cost effective implementation in a small outline package. The device is ready for
use in a large range of applications while the I
2
C
TM
compatible interface provides full control to
a host.
Main Features
3 Channel input device
Proximity & Touch on each channel
I2C
TM
compatible data output
ATI: Automatic tuning to optimum sensitivity
Supply Voltage 1.8V (abs min) to 3.6V (abs max)
Multiple Power Modes
Internal voltage regulator and reference capacitor
Large proximity detection range
Automatic drift compensation
Development tools available (VisualProxSense and USB dongles
ilable
dongles)
Small outline MSOP–10
Applications
White goods and appliances
Office equipment, toys, sanitary ware
Proximity detection that enables backlighting activation (Patented)
Wake-up from standby applications
up
Replacement for electromechanical switches
GUI trigger and GUI control proximity detection
Available options
T
A
MSOP-10
IQS243
-40°C to 85°C
®
IQ Switch
®
ProxSense
®
Series
Functional Overview
1 Introduction
The IQS243 is a three channel capacitive
proximity and touch sensor featuring an
internal voltage regulator and reference
capacitor (Cs).
The device has three dedicated input pins for
the connection of the sense antennas. Three
output pins are used for serial data
communication through the I
2
C
TM
compatible
protocol, including an optional RDY pin.
The device automatically tracks slow varying
environmental changes via various filters,
detect noise and has an Automatic Antenna
Tuning Implementation (Auto - ATI) to tune the
device for optimal sensitivity.
Table 1.1
Pin
1
4
5
2
3
9
10
IQS243 Pin-outs.
Function
IQS243
MSOP 10
VSS
VDDHI
VREG
CX0
CX1
CX2
ADR0
Ground
Power Input
Regulator Pin
Sense Electrode
Sense Electrode
Sense Electrode
I
2
C
TM
Sub
Address
Selection
I
2
C
TM
Ready or
RF input pin
I
2
C
TM
Data
I
2
C
TM
Clock
1.1 Applicability
All specifications, except where specifically
mentioned otherwise, provided by this
datasheet are applicable to the following
ranges:
Temperature -40° to +85°
C
C
Supply voltage (VDDHI) 1.8V to 3.6V
6
RDY
/RF
SDA
SCK
1.2 Pin-outs
7
8
2 Analogue Functionality
The analogue circuitry measures the
capacitance of the sense antennas attached
to the Cx pins through a charge transfer
process that is periodically initiated by the
digital circuitry. The capacitance measurement
circuitry makes use of an internal reference
capacitor Cs and voltage reference (VREG).
The measuring process is referred to as a
conversion and consists of the discharging of
Cs and Cx capacitors, the charging of Cx and
then a series of charge transfers from Cx to
Cs until a trip voltage is reached. The number
of charge transfers required to reach the trip
voltage is referred to as the Current Sample
(CS).
Figure 1.1
IQS243 Pin layout
Copyright © Azoteq (Pty) Ltd 2011.
All Rights Reserved.
IQS243 Datasheet
Revision 1.0
Page 2 of 29
January 2012
IQ Switch
®
ProxSense
®
Series
The analogue
functionality for:
circuitry
further
provides
Initiation of conversions at the selected
rate.
Processing of CS and execution of
algorithms.
Monitoring and automatic execution of the
ATI algorithm.
Signal processing and digital filtering.
Detection of PROX and TOUCH events.
Managing outputs of the device.
Managing serial communications.
Power On Reset (POR) detection.
Brown Out Detection (BOD).
3 Digital Functionality
The digital processing
responsible for:
functionality
is
Management of BOD and WDT events.
Detailed Description
4 Reference Design
Sense Pad1
Cx0
R1
470R
Sense Pad2
VDDHI
Cx1
R2
470R
VDDHI
2
3
9
CX0
CX1
CX2
VDDHI
VREG
4
5
Sense Pad3
R4
4.7K
R3
470R
C1
C3
1uF
C2
100pF
R5
4.7K
R6
4.7K
Cx2
C4
100pF
1uF
I2C_SDA
I2C_SCL
RDY/RF
ADR0
7
8
6
10
SDA
SCK
RDY/RF
ADR0
IQS243
GND
GND
VSS
1
GND
Figure 4.1
Reference Design.
Use C2 and C4 for added RF noise immunity.
Place C1-C4 as close as possible to IC, connected to good GND.
R4, R5 and R6 used as pull up resistors for I
2
C
TM
protocol (4.7k to 10k
typical).
RDY Pin and R6 required for Event Mode.
Refer to Application Note (AZD008) on key pad design.
5 High Sensitivity
Through patented design and advanced signal
processing, the device is able to provide
extremely high sensitivity to detect proximity.
This enables designs that can detect
proximities at a much greater range than other
capacitive sensors. When the device is used
Copyright © Azoteq (Pty) Ltd 2011.
All Rights Reserved.
in the presence of noise or floating metal that
lower the sensitivity, a reduced proximity
threshold is proposed to ensure reliable
functioning of the sensor. The high sensitivity
allows the device to sense accurately through
overlays with low dielectric constant materials
such as wood or even air-gaps.
IQS243 Datasheet
Revision 1.0
Page 3 of 29
January 2012
IQ Switch
®
ProxSense
®
Series
T
TH
=< LTA-CS
Please refer to the Application Note Section
on the Azoteq website for more design tips With lower average CS (therefore lower LTA)
and
other
application
dependent values the touch threshold will be lower and
recommendations.
vice versa. Individual touch threshold can be
set for each channel.
6 Adjustable Proximity
Threshold
8 Charge Transfers
The IQS243 samples in 4 timeslots. The
charge sequence is shown in Figure 8.1,
where CH0 is the Prox channel, which
charges before each of the 3 input channels.
CH0 is realised by connecting all three touch
electrodes with internal switches. Therefore:
CH0 is a distributed electrode formed by the 3
touch electrodes.
The proximity threshold is selected by the
designer to obtain the desired proximity
sensitivity and is selectable between 1 (most
sensitive) to 254 (least sensitive). The IQS243
has a default proximity threshold (P
TH
) of 4 for
all channels. Proximity thresholds for the
sense electrodes are individually adjustable
between the specified limits.
A proximity event is identified when for at least Proximity can be detected by the distributed
6 consecutive samples the following equation electrode (CRX0+CRX1+CRX2) AND each
holds:
individual sense electrode (CRX0, CRX1 and
CRX2).
P =< LTA-CS
TH
Where LTA is the Long Term Average
9 I2C Communication
7 Adjustable Touch
Thresholds
The IQS243 device interfaces to a master
controller via a 2 wire serial interface bus that
is I
2
C
TM
compatible. An optional RDY pin is
The touch threshold is selected by the available to indicate the communication
designer to obtain the desired touch sensitivity window (required for Event Mode).
and is selectable between 1/255 (most
The IQS243 has four available sub addresses,
sensitive) to 254/255 (least sensitive). The
44H (default) to 47H that is selected upon
IQS243 has a default touch threshold (T
TH
) of
purchase of the IC. The ADR0 pin can also be
32/255 (for all 3 channels). The touch
pulled low to increase the I2C address by one
threshold is expressed as a fraction of the LTA
decimal value (for example from 44H to 45H).
as follows:
The
maximum
I
2
C
TM
compatible
T
TH
= Selected Touch Threshold x LTA
communication speed for the IQS243 is
Where LTA is the Long Term Average
400kbit/s.
The touch event is triggered based on T
TH
, CS Please refer to the IQS243 Communications
and LTA. A touch event is identified when for Interface and Sample Code Document for
at least 2 consecutive samples the following further details.
equation holds:
Copyright © Azoteq (Pty) Ltd 2011.
All Rights Reserved.
IQS243 Datasheet
Revision 1.0
Page 4 of 29
January 2012
IQ Switch
®
ProxSense
®
Series
Figure 8.1 Charging and communications sequence for the IQS243.
9.1 Memory Mapping
Address
Size(Bytes)
00h-0Fh
16
R/W
Device Information
R
10h-30h
32
R/W
Device Specific Data
31h-34h
4
Proximity Status Bytes
R/W
R
35h-38h
4
Touch Status Bytes
IQS243 Datasheet
Revision 1.0
R/W
R
Page 5 of 29
January 2012
Copyright © Azoteq (Pty) Ltd 2011.
All Rights Reserved.
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