Azoteq IQ Switch ProxFusion Series User manual

IQ Switch R

ProxFusion R
Series
IQS269A Inductive Sensing Quickstart Guide
Contents
1 Overview 2
2 Design procedure 3
3 Self inductance mode 4
3.1 Example schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2 Example PCB coil layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3 LC tank design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.4 GUIsetup ............................................ 6
4 Mutual inductance mode 9
4.1 Schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2 PCBoutline ........................................... 9
4.3 LC tank design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.4 GUIsetup ............................................ 11
5 Design considerations 14
5.1 Series resistor vs parallel LC tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
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IQS269A Inductive Sensing Quickstart Guide
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IQ Switch R
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ProxFusion R
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1 Overview
The IQS269A device is capable of inductive sensing in both self and mutual inductance modes, with
both these modes requiring the biased configuration for proper operation.Figure 1 and Figure 2 show
the channel configuration for the biased self inductance and biased mutual inductance respectively. In self
inductance mode a channel uses a single coil for both the excitation and sensing. In the mutual inductance
mode each channel has a sensing Rx coil that is mutually coupled to a dedicated excitation Tx coil.
Figure 1: Biased self inductance channel
Figure 2: Biased mutual inductance channel
The device has a total of 8 CX pins that can be configured as either excitation pins (CTx) or sensing pins
(CRx), with the exception of pin CX1 that is set to the bias voltage in inductive sensing mode. Table 1
shows the possible pin assignments of each of the CX pins.
Table 1: IQS269A CX pin assignment in inductive sensing mode
CX pin CTx CRx
CX0 No Yes
CX1 N/A (1)N/A (1)
CX2 Yes Yes
CX3 Yes Yes
CX4 Yes Yes
CX5 Yes Yes
CX6 Yes Yes
CX7 Yes Yes
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IQ Switch R
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The number of available inductive sensor channels that can be used depends on the inductive sensing
mode used. Table 2 shows the available channels for the different sensor modes.
Table 2: IQS269A sensors capabilities for biased configuration
Sensing Mode Available
Channels
Number of
CTx pins
Number of
CRx pins
Bias pin
(CX1)
Total pins
required
Mutual Inductance
(Biased) 6(2)1 6 Yes 8
Self Inductance
(Biased) 3 3 3 Yes 7
For mutual inductance mode with multiple RX sensors, the change in inductance of one sensor by a metal
target affects the inductance value of the other RX sensors since all the coils are mutual coupled to the
same EM field. Due to the coupling, proximity events over a given sensor should be registered as a relative
change in the inductance. For the self inductance mode, the sensors are not coupled and thus a proximity
event over a sensor can be registered as the absolute change in inductance.
Design choice between mutual and self mode is primarily dependant on the inductive sensing application.
Multiple sensors in the self inductance mode should be used for applications that require absolute read-
ings. Such applications include, encoded event triggers that require a given high-low sequence across the
sensors to register a particular event. Multiple sensors in the mutual inductance mode should be used for
applications that do not require absolute readings. Such applications include, linear position sliders that
indicate the position of a metal target over multiple sensors.
2 Design procedure
•Depending on the inductive sensing application, select either the mutual or the self inductance sens-
ing mode. Refer to Table 2 for the available sensor channels in each mode.
•Determine maximum sensing distance hand design sensor coils with smallest outer diameter Dout
such that Dout ≥2h.
•Select number of turns on each coil such that each coil has the recommended inductance value of
at least 0.5µH. Sensing can be achieved with smaller inductance values, however careful tuning of
the tank circuit and device setting is required. A larger inductance value has little significance on the
sensing range but provides better noise performance.
•Implement parallel LC tank circuit with resonant frequency fres.
fres =
1
2π√LC (1)
For the mutual inductance mode, the LC tank can either be implemented on only the Tx coil or on
both the Tx and Rx coils for greater sensitivity.
•Select capacitor value Csuch that fres and the coil excitation frequency ftx satisfy the response
condition
fres ≥ftx (2)
1CRX1 pin is configured as the bias voltage in inductive sensing mode
27 channels if CTx signal is provided externally (E.g. PWM from an MCU)
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IQS269A Inductive Sensing Quickstart Guide
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IQ Switch R
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ProxFusion R
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3 Self inductance mode
Self inductance mode for the IQS269A requires the biased sensing configuration, where pin CRX1 pro-
vides the bias voltage. Each sensor channel has a CTx pin and a corresponding CRx pin.
3.1 Example schematic diagram
Figure 3: Schematic for 3 self inductance sensors
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IQ Switch R
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3.2 Example PCB coil layout
Figure 4: PCB coil dimensions
3.3 LC tank design
The value of parallel capacitor Cat each of the coils should be selected to satisfy the response condition
fres ≥ftx. For this example design ftx is set to 16 MHz. Form Equation (1), the response condition is
satisfied when C≤660 pF.
Due to tolerance in the capacitor value, its good design practice to select a capacitor value that is slightly
smaller than the upper limit. This ensures that the response condition is met and the fres is as close as
possible to ftx which translates to less signal attenuation. Selecting standard capacitor value of 560 pF
±10% satisfies the response condition.
The design and LC tank tuning parameters of the rectangular PCB coils shown in Figure 4 are given in
Table 3.
Shape Rectangle
Length 7.00 mm
Width 4.00 mm
Number of turns 6
Trace width 0.15 mm
Trace spacing 0.15 mm
Measured inductance (L) 0.14 µH
Parallel capacitor (C) 560 pF ±10%
fres 18 MHz
ftx 16 MHz
Table 3: Rectangular PCB coil design parameters
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IQ Switch R
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ProxFusion R
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3.4 GUI setup
a) Start Streaming and launch user settings window.
b) Enable CH0, CH1 and CH2
c) Set MCU FOSC to 16 MHz
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IQ Switch R
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d) Set ftx to 16 MHz
e) Configure CH0
f) Configure CH1
g) Configure CH2
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h) Write changes to devices
i) Acknowledge reset and redo ATI.
j) Expected streaming data.
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IQ Switch R
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4 Mutual inductance mode
Mutual inductance for the IQS269A requires the biased sensing configuration. In inductance mode the
device automatically enables pin CX1 as the bias point.
4.1 Schematic diagram
Figure 5: Mutual inductance sensing schematic diagram
4.2 PCB outline
Figure 6: Mutual inductance PCB coil layout
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IQ Switch R
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4.3 LC tank design
The same procedure as given in Section 3.3 is followed for calculating the parallel tank capacitor. The
Cvalue is chosen such that response condition fres ≥ftx is satisfied. The design and LC tank tuning
parameters for the Tx and Rx PCB coils are given in Table 4 and Table 5 respectively.
Table 4: Tx circular shaped PCB coil design parameters
Shape Circle
Diameter 17.65 mm
Number of turns 4
Trace width 0.15 mm
Trace spacing 0.15 mm
Measured inductance (L) 0.61 µH
Parallel capacitor (C) 2.2 nF ±10%
fres 4.3 MHz
ftx 4 MHz
Table 5: Rx arc shaped PCB coil design parameters
Shape Arc
Angle 120◦
Radius 7.47 mm
Number of turns 9
Trace width 0.15 mm
Trace spacing 0.15 mm
Measured inductance (L) 0.72 µH
Parallel capacitor (C) 1.5 nF ±10%
fres 4.8 MHz
ftx 4 MHz
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IQS269A Inductive Sensing Quickstart Guide
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IQ Switch R

ProxFusion R
Series
4.4 GUI setup
a) Start Streaming and launch user settings window.
b) Enable CH0, CH1 and CH2
c) Set MCU FOSC to 16 MHz
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IQ Switch R

ProxFusion R
Series
d) Set ftx to 4 MHz
e) Configure CH0
f) Configure CH1
g) Configure CH2
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IQ Switch R

ProxFusion R
Series
h) Write changes to devices
i) Acknowledge reset and redo ATI.
j) Expected streaming data.
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IQS269A Inductive Sensing Quickstart Guide
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IQ Switch R
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ProxFusion R
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5 Design considerations
5.1 Series resistor vs parallel LC tank
It is always recommended to use the parallel LC tank circuit at the excitation coil. However, a series resistor
can help in reducing the amount of EM emissions while still providing a sufficient sensing signal. This is
helpful in cases where EMC compliance required.
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IQ Switch R

ProxFusion R
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Contact Information
USA Asia South Africa
Physical 6507 Jester Blvd Rm1227, Glittery City 1 Bergsig Avenue
Address Bldg 5, suite 510G Shennan Rd Paarl
Austin Futian District 7646
TX 78750 Shenzhen, 518033 South Africa
USA China
Postal 6507 Jester Blvd Rm1227, Glittery City PO Box 3534
Address Bldg 5, suite 510G Shennan Rd Paarl
Austin Futian District 7620
TX 78750 Shenzhen, 518033 South Africa
USA China
Tel [phone] [phone] [phone]
ext 808
Fax [phone] [phone]
Email inf[email protected] [e-mail] inf[email protected]
The following patents relate to the device or usage of the device: US 8,395,395; US 8,659,306; US
9,209,803; US 9,360,510; US 9,496,793; US 9,709,614; US 9,948,297; EP 2,351,220; EP 2,559,164; EP
2,748,927; EP 2,846,465; HK 1,157,080; SA 2001/2151; SA 2006/05363; SA 2014/01541; SA
2017/02224;
AirButton R
, Azoteq R
, Crystal Driver R , IQ Switch R , ProxSense R , ProxFusion R , LightSenseTM,
SwipeSwitchTM, and the logo are trademarks of Azoteq.
The information in this Datasheet is believed to be accurate at the time of publication. Azoteq uses reasonable effort to maintain the information up-
to-date and accurate, but does not warrant the accuracy, completeness or reliability of the information contained herein. All content and information
are provided on an “as is” basis only, without any representations or warranties, express or implied, of any kind, including representations about
the suitability of these products or information for any purpose. Azoteq disclaims all warranties and conditions with regard to these products
and information, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and
non-infringement of any third party intellectual property rights. Azoteq assumes no liability for any damages or injury arising from any use of
the information or the product or caused by, without limitation, failure of performance, error, omission, interruption, defect, delay in operation or
transmission, even if Azoteq has been advised of the possibility of such damages. The applications mentioned herein are used solely for the
purpose of illustration and Azoteq makes no warranty or representation that such applications will be suitable without further modification, nor
recommends the use of its products for application that may present a risk to human life due to malfunction or otherwise. Azoteq products are
not authorized for use as critical components in life support devices or systems. No licenses to patents are granted, implicitly, express or implied,
by estoppel or otherwise, under any intellectual property rights. In the event that any of the above-mentioned limitations or exclusions does not
apply, it is agreed that Azoteq’s total liability for all losses, damages and causes of action (in contract, tort (including without limitation, negligence)
or otherwise) will not exceed the amount already paid by the customer for the products. Azoteq reserves the right to alter its products, to make
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