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E909.01
DESIGNING SYSTEMS WITH HALIOS® SWITCH
Scope
Features
This application note provides information about how
to design systems with the HALIOS®switch E909.01
and gives examples of schematics and appropriate
surface materials.
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The HALIOS® principle highly improves sensitivity and
robustness against disturbances of sensor systems.
Therefore it is possible to realize, e.g. touch or
approach detection systems based on a capacitive
working principle even in metal shielded environment
or optical input devices under high ambient light conditions. The E909.01 is an optical switch which is able
to suppress the influence of ambient light by using
the HALIOS® working principle. The device detects the
rapprochement of objects and additionally indicates
when the object touches the surface. These functions
are available on the device pins PROX and Touch.
Further, the corresponding measurement values can
be readout via SPI interface. Elmos recommands the
integrated optical module TCND3000 for optimized
optical sensitivity.
Applications
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Waterproof switches
Switch for anti-septic environment
Switch with background lighting function
Proximity sensing
Optical key pad array
�
VDD
DS_obj
100µF
DVDD
DVDD
Filter
Demod.
TIN
SCK
SPI
VDD
VDD
VDD
Touch a / LDB
Photodiode
DS_int
IR-Emitter LEDC
(Compensation)
Touch b / MISO
LEDS
DC
500
DS = DS_int + DS_surf + DS_obj
LEDC
IR-Emitter LEDS
(Transmitter)
MOSI
100k
DS_surf
100µF
AVDD
500
Translucent
surface
VDD
10
General Description
Two outputs for Proximity and Touch function
SPI interface for measurement data
Selfcalibration capability
Operational up to 200klux ambient light
Package SOP16 or TSSOP16
Supply voltage: 3.3V to 5.0V
– 40°C to +85°C operating temperature
EN_SPI
control
TCND3000
SWTO
SYI
LEDC
TIN
GND
LEDS
PROX
SYO
200pF
AVSS
ELMOS Semiconductor AG
Application Note
1/39
DVSS
QM-No.: 03AN0801E.01
ELMOS Semiconductor AG
Application Note
2 /39
yes
Capacitive
Certain force necessary
no
Possibility to change
functionality via SW
yes
no
no
no
restricted
restricted
no
yes
Huge effort
yes
yes
no
no
Depending on surface
yes
yes
yes
Huge effort
no
no
no
Certain force necessary
Restricted temperature range
no
restricted
no
no
restricted
no
restricted
Medium effort
no
Resistive
yes
Light touch of surface,
even gesture recognition
yes
yes
yes
yes
yes
yes
yes
All IR transparent
colors
and surface possible
Exremely low effort
yes
HALIOS®(optical)
0 mm
0 mm
0-50mm or more
Positive fit necessary Positive fit necessary depending on the
setup
yes
Piezo-electric
Touch of surface suf- Certain force necesficient
sary
yes
yes
restricted
no
Depending on surface
no
yes
yes
Medium effort
0 mm
Several mm´s
Positive fit necessary
no
Mechanical
Required operation
force
Resistance against
influences by temperature changes
Resistance against
influences by ageing
Possibility to differentiate between
certain gestures
Possibility of far
distance detection
Resistance against
chemicals and
liquids
Operation under
humid conditions
Resistance against
mechanical wear
Printability of
surface
Possibility to change
arrangement of
elements (e.g.
exchangeability of
surface)
Possible distance
between actuator
and surface
Integration under
Solid Surface
Parameter
E909.01
System Comparison
QM-No.: 03AN0801E.01
E909.01
SOP16 Package Outline and Description
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16
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Figure: Pin-Out E909.01
Pin Description
Pin Nr.
Name
Type 1)
Function
1
AVDD
AI
Analogue supply
2
TIN
AI
Transimpedance amplifier input
3
AVSS
AG
Analogue ground
4
LEDC
AO
Output compensation LED
5
DVSS
DG
Digital ground
6
LEDS
AO
Output Sending LED
7
DVDD
AI
Digital supply
8
ENSPI
DI
Enable the SPI Interface
9
SWTO
DI
Select touch or toggle mode
10
TOUCH_A/
LDB
A I/O
DI
Output of the “Touch” function with an analogue switch of typically
30Ω between pin 10 and pin 11. In SPI operation mode (ENSPI=HIGH)
this pin redefindet to the LDB “chip select” output
11
TOUCH_B/
MISO
A I/O
DZ
12
SYO
DZ*
Synchronisation output (*high resistance for a short timer after
power on and SPI Reset)
13
PROX
DI
“Proximity” function output (active low)
14
SYI
DI
Synchronisation input
15
MOSI
DI
SPI “master output slave input”
16
SCK
DI
SPI serial clock
Output of the “Touch” function with an analogue switch of typically
30Ω between pin 10 and pin 11. In SPI operation mode this pin redefindet to the MISO “master input slave output” output
1) A = Analog, D = Digital, G = Ground, I = Input, O = Output, I/O = Bidirectional and Z = Tristate Output
ELMOS Semiconductor AG
Application Note
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QM-No.: 03AN0801E.01
E909.01
SOP16 Package Outline
N
-BE
Index Area
H
Detail 'B'
1 23
h X 45º
Detail 'A'
α
L
Detail 'B'
e
A
-CSeating
Plane
A1
D
Mould Parting
Line
C
-A-
B
Detail 'A'
TSSOP16 Package Outline
D
N
E
C
9
E1
Index Area
8
1
E
h
L
A2
A
A1
ELMOS Semiconductor AG
phi
Seating
Plane
B
Application Note
4 /39
QM-No.: 03AN0801E.01
E909.01
1 Optics
1.1 Optical Operation Principle
The HALIOS®-switch is based on the principle of a reflective light barrier. A LED transmits light into the surrounding area. This light is partly reflected by a translucent surface and an approaching finger. The reflected light is
then received by a photodiode. Thus the system consists of two optical couplings: one fixed predetermined by
the setup, mainly the surface, and one predetermined by an approaching finger. Let’s take a closer look at the
character of a finger. A finger can be characterised as a reflector with Lambertian characteristics. Figure 1.1 shows
some samples of diffuse reflection of human skin (variations due to various reflexion grades).
Figure 1.1: Diffusion of human finger
The diffusion of the human skin is characterised by an area ranging from blue to green (about 590 nm) with a
low diffuse reflection and an area from red to infrared with high diffuse reflection. This characteristic step is
generated by the colour of blood and independent of the colour of skin. Consequently the use of red or infrared
LEDs for the HALIOS®-switch should be preferred. This spectral range also fits ideally the low priced silicone photodiodes. The TCND 3000 module uses a wavelength of 885 nm. The reflection of clothes in the IR range can not
be derived from the visible appearance as shown in Figure 1.2.
ELMOS Semiconductor AG
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QM-No.: 03AN0801E.01
E909.01
Figure 1.2: Diffusion of some clothes
The area, where the touch is supposed to take place, is illuminated by the transmitting LED and observed by the
photodiode. The definition of this area is predetermined by the optical setup, especially the overlapping of radiation and receiving characteristics of the sending LED and photodiode. The sensitivity of the system is specified by
a change between the received light resulting from an approaching finger in comparison to the received signal,
when no object is near the surface. The setup using the TCND3000 is shown schematically in figure 1.3.
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QM-No.: 03AN0801E.01
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E909.01
DS_obj
Translucent
surface
DS_surf
IR-Emitter LEDS
(Transmitter)
DS = DS_int + DS_surf + DS_obj
Photodiode
DS_int
IR-Emitter LEDC
(Compensation)
DC
LEDC
TIN
GND
LEDS
TCND3000
Figure 1.3: Schematic setup with TCND 3000
The light can take three different ways between the transmitting LED to the receiving photodiode. The first way
is predetermined by the TCND 3000 module itself (optical coupling DS_int), the second is fixed by the set-up (DS_
surf) and the third way is defined by the finger (DS_obj). The internal coupling of the module is designed for stable
operation of the IC E909.01. The reflection resulting from an approaching finger, however, should be greater
than the one resulting from the internal setup. Please note that every surface gives an additional reflection. The
situation can be simulated with ray tracing using a reflector with Lambertian surface characteristics substituting
a finger. It is also possible to use an analytical description. The radiation characteristic of a LED or the receiving
characteristic of a photodiode is in good approximation given by:
Φ=Φ0 cosκ (ϕ)
Equation 1.1
The exponent κ is given by the half power angle ϕ0.5:
κ=
In (0.5)
In (cos(ϕ 0.5))
Equation 1.2
The transmitting LED and the receiving LED have both a half angle of 20°, consequently κ is approximately 11. The
finger can be characterised as a Lambertian reflector described by the equation 1.1 by setting κ to 1.
To provide a well working system, it is necessary to arrange the optical couplings DS and DC (cf. figure 1.3) in a
certain ratio and a certain range. The optical coupling is given by the ratio of the received light power compared
to the transmitted light power. Especially the ratio of the two parts of DS should lie within a certain range. For
more details, please refer to the next chapter.
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QM-No.: 03AN0801E.01
E909.01
1.2 Optical and Geometrical Design
Let’s take a closer look at the HALIOS® - control constraint. The control constraint requires that the photodiode
has to “see” the same light intensity from both light sources (LEDs). The ELMOS IC E909.01 controls the current
of the LEDs. These currents are then translated into light intensity (kLED). The current produced inside the IC is
controlled by a DAC driven from the LOOP-Value n. The transfer factor is 10 or 20 mA (Imax_s) nominal full range
for the transmitting LED and 1 or 2 mA (Imax_c) nominal full range for the compensating LED. It is also possible to
choose between two control principles. One controls both LEDs against each other (X-control) and the other determines the intensity of the transmitting LED on a fixed level (Y-control).
The system is described by the following equations:
For X-control
Imax_S nmax-n kLED DS = Imax_C n kLED DC
nmax
nmax
Equation 1.3
For Y-control
Imax_S kLED DS = Imax_C n
kLED DC
nmax
Equation 1.4
To balance both equations it is necessary to take the ratios of the optical coupling D and the ratio of the current ranges Imax into account. The Y-control clips if the ratios are out of balance. The X-control works under any
circumstances, but “compresses” the Loop signal to fit into the range from zero to nmax. The ratio of the current
ranges can be chosen via parameters in three steps:
Imax_C
={0.05, 0.1, 0.2}
Imax_S
Equation 1.5
Consequently the ratio of the optical couplings should fit this range. Normally it is not very easy to adjust the
LEDs correctly to meet the specification of DC and DS. Using the TCND 3000 one can save oneself the difficult
adjusting work, as the development of the module already took this into consideration. The optical couplings are
adjusted in such a way, that a finger can be detected in a range of 1 to up to 20 mm`s.
The absolute value of the optical couplings determines the noise and proximity distance. Inside the TCND 3000
the values of the optical couplings are fixed reliable levels.
Using the SPI interface it is possible to read the Loopvalue n. This value contains all information about the system. Here are some hints to qualify the signal:
ÿ noise (difference between min and max-value) without an object: about 2 to 6
ÿ Loopvalue without an object: 100 to 400
ÿ Change of Loopvalue with Object (finger): > 100
Always evaluate the combination of surface material and distance to the module.
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QM-No.: 03AN0801E.01
E909.01
Figure 1.4: Basic arrangement using TCND 3000 module supplied by VISHAY®
The resulting photodiode current depending on the distance of an object (representing a finger) to the TCND
3000 is shown in figure 1.5. Please note that the compensating LED causes a photodiode current of zero to up to
5 µA depending on the loop value.
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E909.01
Figure 1.5: Photocurrent caused by reflection vs. distance. (cf. VISHAY® datasheet figure 5)
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E909.01
1.3 Surface materials and mechanical set-up
It is possible to use a wide variety of materials for the surface, however, some constraints have to be taken into
account. These constraints can be divided into two groups according to their mechanical or material properties.
Mechanical constraints:
ÿ The surface should not move relative to the optic, otherwise the Touch-Algorithm does not work properly
ÿ The surface should be mechanically stable
ÿ The surface should fit the requirements of mechanical and chemical stability for your application
ÿ The surface should give the user a mechanical orientation, like a dent or a grove.
ÿ This haptic feedback improves the mobility.
Material constraints:
There are three parameters of the material that should not get mixed up. The visible transparency of a material is determined by two effects: the absorption in the volume and the diffusion in the volume. The last material parameter is the diffusion by surface roughness. Nearly all artificial materials are transparent in the visible
and near IR range. The transmitted light power is additionally influenced in fully clear materials by the refractive
index (Reflexion given by the Fresnell Law). Consequently the transmission can reach a maximum of approximately 92% for PMMA. There are a lot of pigments and colouring dyes. Organic dyes give the visible colour by
absorbing some parts of the visible spectral range. They normally do not absorb in the infrared range. Inorganic
dyes are enclosed particles and give a diffusion of the material. This diffusion exists also in the infrared range.
Especially the colour white is always created by diffuse wavelength independent reflexion. Diffuse surfaces and
printing on surfaces gives additional diffusion.
The target is to get as much IR light as possible through the surface and to influence the focusing of the optoelectronic components as little as possible.
Table 1.1 gives a rough overview about materials well suited for switch applications.
Type
Supplier
Colour
PMMA N6 N7 N8962
Degussa Roehm®
clear
PMMA white 010
Degussa Roehm®
white
PMMA white 017
Degussa Roehm®
white
PMMA 962 (PERSPEX®)
ICI®
black
PMMA blue 627
Degussa Roehm®
blue
PMMA 7704 (PERSPEX®) ICI®
blue
PMMA red 555
red
Degussa Roehm®
PMMA 4401 (PERSPEX®) ICI®
Transmitter with small half power angle
and directly mounted to the surface
Transmitter with small half power angle
and directly mounted to the surface
red
PMMA green 777
Degussa Roehm®
green
Plexiglas Satinice®
clourless
Degussa Roehm®
diffuse
Macrolon® Ft: 450601 Bayer®
Remark
black
Transmitter with small half power angle
and directly mounted to the surface
Table 1.1 : Samples of tested materials
ELMOS Semiconductor AG
Application Note
11 /39
QM-No.: 03AN0801E.01
E909.01
1.4 Design Rules
To build up a well working switch please take the following steps:
1. Compile your set-up and read out the Loop-signal
2. Select the kind of surface material, surface roughness and distance in such a way that the
Loopsignal ranges between 100 and 400
3. Control the Loopsignal noise (good is 2 to 6 peak to peak)
4. Place your finger on the switch. The Loopsignal should change a minimum of 100 and not go to saturation
5. Repeat step 2.
Here are some hints concerning the selection and adjustment of the components:
ÿ Diffuse material or a rough surface
put the material as close as possible to the TCND 3000 module
ÿ Signal change by finger too low
decrease Loop-value without finger, reduce surface reflexion; change default state of transmitter
and compensator currents
ÿ Proximity distance too small
use non diffuse surface material; reduce surface reflexion
ÿ Noise too high
this is caused by a low energy at the photodiode. Increase power of transmitter by increasing the current
with a current mirror
ÿ Proximity-signal without an object
this is caused by a top high noise. Also a modulated light source with HALIOS® frequency (125 kHz) can
cause this problem
ÿ A touch is not detected
check the amplitude in the LOOP-Signal and the stability of the signal. Check the mechanical stability
of the surface.
ÿ The system is sensitive to ambient light
reduce the noise of the LOOP-signal; increase the system power by LED current; check the DC photodiode current (less than 1mA); check for modulated ambient light sources; use photodiode with filter
ÿ Effect of FIXS configuration
by setting the FIXS configuration the touch amplitude is in most cases doubled, but the system is more
sensitive to the mechanical adjustment
ÿ Effects of HICS and HICC
enabling or disabling both, gives the same sensitivity except that by enabling both the noise increases.
Enabling HICS and disabling HICC gives a sensitive system and disabling HICS while enabling HICC
leads to a very stable system
ELMOS Semiconductor AG
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QM-No.: 03AN0801E.01
E909.01
1.5 Advanced configuration
In some special cases it might not be possible to achieve a proper functioning via adjusting the LED currents
using the SPI commands or it might not be possible to change the mechanical setup. In such rare cases it could
be helpful to adjust the LED currents very precisely. Therefore use a current mirror circuit as shown in figure 1.6.
The depicted values are a very good starting point, but should be adjusted to your application.
VDD
680
VDD
27
BC857
To 909.01
pin 2 (TIN)
GND
GND
TIN
VDD
1k
VDD
2.2k
adjust
LEDC
Photodiode
GND
270
TCND3000
150
IR-Emitter LEDS
(Transmitter)
LEDS
BC846
IR-Emitter LEDC
(Compensation)
To 909.01
pin 6 (LEDS)
BC857
To 909.01
pin 4 (LEDC)
BC846
1.8k
GND
2.2k
adjust
GND
Figure 1.6: Current mirror circuit (shown values are a very good starting point)
In case of a very high backscattering from the surface to the module, adjusting the currents will not solve the
problem. In such cases the insertion of an additional shielding between the transmitter and the receiver might
be a better solution. This can be reached only by filling the grove in the module between transmitter and receiver by using black epoxy glue (Please make sure that the glue is really IR absorbing), or by introducing a mechanical shielding from the module up to the surface. These two possibilities are shown in figure 1.7. If you use such a
set-up please test appropriately and keep the tolerances in mind.
ELMOS Semiconductor AG
Application Note
13 /39
QM-No.: 03AN0801E.01
E909.01
Scattering
surface
Filling of IR
absorbing
epoxy glue
Mechanical
shield made of
black plastic
Photodiode
IR-Emitter LEDC
(Compensation)
IR-Emitter LEDS
(Transmitter)
IR-Emitter LEDC
(Compensation)
Possibility 1
LEDC
GND
LEDS
LEDC
TCND3000
TIN
GND
LEDS
TCND3000
Photodiode
TIN
IR-Emitter LEDS
(Transmitter)
Possibility 2
Figure 1.7: Introduction of optical shielding
ELMOS Semiconductor AG
Application Note
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QM-No.: 03AN0801E.01
E909.01
2 Working Principle ASIC
2.1 Block Diagram
DVDD
AVDD
DVDD
TIN
Filter
Demod.
SCK
SPI
MOSI
Touch a / LDB
LEDC
Touch b / MISO
LEDS
EN_SPI
control
SWTO
PROX
SYI
SYO
AVSS
DVSS
Figure 2.8: Block Diagram E909.01
The high ambient light suppression using the HALIOS® principle is based on two light sources which are clocked
by inverted phases. The photo-current receiver amplifies the difference of the received signal in both clock phases and modulates the light source intensity in a negative feedback loop in order to compensate the received signal to zero. Thus the input amplifier is always regulated to its most sensitive operation condition independent of
the ambient light conditions.
The receiving path uses a transimpedance amplifier with DC-current control to transfer the photo current into a
voltage. The signal is then amplified and filtered to remove disturbing signals and amplifier offsets. The demodulator samples the voltages at the output of the amplifier synchronously to the LED clocks, takes the difference
of the signal in phase A and phase B and delivers the sign of this difference to the digital integrator.
The transmitting path produces the signals for the LED modulation by converting the integrator output to an
analogue voltage. The output drives the compensation LED (LEDC) as shown in figure 2.1 with a voltage controlled current source of maximum 1.5mA output current. The sending LED (LEDS) is driven by a constant current of
10mA. Both outputs are then clocked synchronously to the demodulator.
The detection algorithm analyses the data sequence of the digital integrator to detect whether an object is simply approaching the sensor or if it is actually touching the surface of the switch.
ELMOS Semiconductor AG
Application Note
15 /39
QM-No.: 03AN0801E.01
E909.01
2.2 Overview Basic Functions
When an object appears in the detection range of the sensor the signal PROX is activated. If a touch occurs on
the sensor surface a signal is given by closing an analogue switch of 40 Ohm between the pins TOUCH_a, and
TOUCH_b. With a wipe over the sensor surface the detection algorithm is reset.In order to reduce the current
consumption the measurement cycle is activated only for a short time Tmeasure.
During the passive time Tpassive the IC is switched to an operation mode with reduced current consumption.
When an object is in the detection area of the sensor the proximity signal is activated and the sampling rate is
high. If no object is detected the sensor is switched to stand-by mode with reduced sampling rate in order to
minimize the mean current consumption.
To change this default configuration a full bidirectional SPI interface consisting of the pins LDB, SCK, MOSI and
MISO can be activated with the pin ENSPI. It is possible to adjust several thresholds and time constants which
are used for the proximity, touch and wipe function. Additionally it is possible to read back data from the switch
to the supervising µ-Controller In this case the output of the digital integrator can be observed directly by the µC
and it is possible to implement different algorithms for signal detection.
If several switches are positioned in close range of each other, the measurement phases can be synchronised in
order to minimise disturbances between the switches. The synchronisation bus consists of the pins SYI and SYO
and connects all switches in a loop.
2.2.1 Synchronisation
The synchronisation is reached by passing a pulse from one switch to the next. The sensor which has activated
the measurement cycle switches the output SYO to ‚HIGH‘. Then the first switch delays the new cycle until the
passive time Tpassive has passed. The first switch is defined with a pull-up resistor at pin SYO. The synchronisation
leads to a reduced noise and improves the ambient light suppression.
If the synchronisation pulse is observed by the µC it is possible to reduce the noise caused by the communication
by delaying the SPI commands until the measurement cycles are finished.
2.2.2 Active - and Stand-by - Operation Mode
To reduce the current consumption the measurement phase is only activated for a short time of 25 clock periods
(200 µs) and the LEDs are clocked with 125 kHz. Together with a settling time for the amplifiers the total measurement time has a value of Tmeasure = 464 µs. Afterwards during the passive time the measurement is stopped
and the LEDs are switched off. When an object (movement) is detected and the proximity signal becomes ‚0‘
the sensor is in the active operation mode for a minimum of 260 ms (minimum active time). In this case the
measurement is activated with a rate of 244 Hz. When no movement is detected during this time the sensor is
switched to stand-by mode and the sampling rate is reduced to 15 Hz. If the object is still in the detection area
(without a movement) the PROX-output stays active (‚0‘), independent of the operation mode (default).
By connecting the PROX output to the interrupt pin of the supervising µC, it is possible to use the proximity
event as a wake-up signal for the µC.
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E909.01
2.2.3 Detection Algorithms
The algorithms to detect a switch event are observing the integrator output which is proportional to the modulation current of the compensation LED. If no object is in the detection area of the sensor and the regulation
loop has settled, the integrator signal has a static value. If an object approaches the sensor the integrator output
changes its value. As soon as a certain threshold value is reached the proximity signal PROX is activated.
To detect a touch event the 1st and 2nd derivatives of the integrator output are used additionally. These values
are functions of the object´s velocity and acceleration. A touch is detected if the object is approaching with a
minimum velocity, stops on the sensors surface with a minimum of negative acceleration and remains on the
surface of the sensor without moving after the touch for a minimum time of 130 ms (can be adjusted with the
parameter TOTIM in table 2.2). This time criterion is used to assure that the indented touch is really detected as
such.
If the object is removed from the sensor surface the stand-by mode is activated again as soon as the output of
the integrator reaches the old value which it had before entering the active mode. If something should fall onto
the surface and activate the TOUCH, a time-out function switches back into stand-by mode after global time
out (TIMOV – descr. in table 2.2) and the recent static value of the integrator output is used as new reference
value for the proximity function.
The TOUCH signal output (on pins 10 and 11 or via SPI) depends on the pin SWTO. When this pin is connected to
ground, TOUCH is only active as long as the object touches the surface (touch-mode). When it is connected to
supply, it is in toggle-mode: A TOUCH event closes the switch and the TOUCH output stays active as long as the
next TOUCH event opens the switch.
With a wipe over the sensors surface the detection algorithm is reset. If after a touch some dirt should remain
on the sensor, the system will not turn to stand-by mode due to a higher reflection. In this case a wipe stops the
time-out and a new reference will be found.
2.3 SPI Interface
16 data bits are sent to the E909.01 via SPI. The first four bits contain the address bits. These four bits tell the
E909.01 its general operation. The next four bits contain the Data information. The last eight bits are not used.
The SPI interface consists of 4 pins:
1. MOSI : Master Out Slave In : µC => ASIC
2. SCK : Serial Clock : µC => ASIC
3. LDB : Load (active low): µC => ASIC
4. MISO : Master In Slave Out : ASIC => µC
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QM-No.: 03AN0801E.01
E909.01
2.3.1 SPI Transmission
Each transmission starts with a falling edge on LDB and ends with a rising edge. During transmission commands
and data are shifted according to the following rules
1.
2.
3.
4.
LDB line is active (active ‚LOW‘)
MOSI data are shifted in on the rising SCK edge MSB first and LSB last
MOSI data are read on the falling SCK edge.
A command is only carried out on the rising edge of LDB when 16 clock cycles are counted during the last
transmission.
5. MISO is active when LDB is ‚LOW‘ and is tristated when LDB is ‚HIGH‘.
6. SCK should remain ‚LOW‘ after the 16th SCK falling edge.
The following diagram shows one data transmission over the SPI-bus. For exact timing please refer to the specification 03SP0277E.
Figure 2.9: Example of a correct data transmission, command h2200
2.3.2 MISO Line
16 bits of Data are returned to the µC on the rising edge of SCK. The returned data contains information concerning the state of the switch and the value of the DAC or the received command. This depends on the parameter
RETUR (default ‚LOW‘).
RETUR
MISO LINE
MSB[1]
[2]
[3]
[4]
[5]
[6:13]
‘LOW’ not STANDBY MOVEDO PRETO TOUCH WIPE COUNT[9:0]
‘HIGH’ not STANDBY MOVEDO PRETO TOUCH WIPE ADDR[0:3]
[14]
[15]
LSB[16]
TMODE
DATA[0:3] RETUR TMODE TMODE
Table 2.2
In the example of figure 2.2 the received bits are: 1110001111111110 (with default parameters).
This means the E909.01 is in active mode (internal PROX, here: high active!), the states MOVEDO and PRETO are
low active and TOUCH, WIPE are high active. The integrator value is COUNT=“0111111111“(511) and the LSB: TMODE
(high active) indicates that the E909.01 is not in test-mode.
ELMOS Semiconductor AG
Application Note
18 /39
QM-No.: 03AN0801E.01
E909.01
Bit Position
Name
MSB
MOTION
Bit (14)
MoveDown*
Bit (13)
PreTouch*
Bit (12)
TOUCH
Bit (11)
WIPE
Description
This bit is activated when an object is moving inside the sensor area.
Once the object remains still the signal is deactivated.
This signal is activated when the minimum TOUCH level(THZ2) and the
minimum velocity level(THD1) have been reached.
This signal is activated when MoveDown is active and the deceleration
remains under the THA level(This parameter is coupled with THD1).
If the signal remain in the state PreTouch for the required
TouchTime(TOTIM) the Touch signal is activated.
This signal is activated when an object slides quickly over the sensor
surface.
RETUR = ‘0’
RETUR = ‘1’
Bit (10)
->
COUNT (9)
ADDR (3)
Bit (9)
->
COUNT (8)
ADDR (2)
Bit (8)
->
COUNT (7)
ADDR (1)
Bit (7)
->
COUNT (6)
ADDR (0)
Bit (6)
->
COUNT (5)
DATA (3)
Bit (5)
->
COUNT (4)
DATA (2)
Bit (4)
->
COUNT (3)
DATA (1)
Bit (3)
->
COUNT (2)
DATA (0)
Bit (2)
->
COUNT (1)
NA
Bit (1)
->
COUNT (0)
NA
LSB
TESTMODE
This bit indicates that the ENSPI pin is at half of VDD. It is now possible to
conduit the productional tests.
Note: Signals marked with * are active low; all others are active high.
Data is shifted out on the rising SCK edge starting with MSB.
WIPE:
This signal RESETs the detection algorithm to it default state. If in TOGGLE mode(set with pin SWTO)
an active TOUCH signal will not be RESET unless the SPI cmd. 0X1B** has been sent (RSWIPE).
RETUR:
This bit determines the value that is returned over the SPI interface. With the SPI cmd 0X1C**
the COUNT value is returned, and with the SPI cmd. 0X1D** the data returned contains the last SPI cmd
that was received.
ELMOS Semiconductor AG
Application Note
19 /39
QM-No.: 03AN0801E.01
E909.01
2.3.3 Address decoding
Address
“0000”
Data
Hex
Default
Signal
“0000”
00**
-
-
-
unused
“0001”
01**
-
-
-
unused
“0010”
02**
-
-
-
unused
“0011”
03**
-
-
-
unused
“0100”
04**
-
-
-
unused
“0101”
05**
-
-
-
unused
“0110”
06**
“0111”
07**
enabled
G0
“1000”
08**
“1001”
09**
disabled
G1
“1010”
0A**
“1011”
0B**
enabled
HICC
“1100”
0C**
“1101”
0D**
disabled
HICS
“1110”
0E**
“1111”
0F**
disabled
FIXS
ELMOS Semiconductor AG
Description
disabled
enabled
disabled
enabled
disabled
enabled
disabled
enabled
disabled
enabled
Application Note
20 /39
Gain setting 6dB.
Gain setting 12dB.
High current for compensation LED.
High current for sending LED.
Fixed current for sending LED.
QM-No.: 03AN0801E.01
E909.01
Address
Data
Hex
“0000”
10**
“0001”
11**
Default
Signal
Description
disabled
enabled
ACC_ON
enabled
En/Disabled the counters acceleration
(see 4.1).
-Enabled -> step size: 1-8 LSD.
-Disabled -> step size: 1 LSB.
“0001”
“0010”
12**
“0011”
13**
“0100”
“0111”
14**
17**
“1000”
18**
“1001”
19**
“1010”
1A**
“1011”
1B**
“1100”
1C**
4 LSB
SELACC
-
-
disabled
SELDELAY
disabled
RSWIPE
return
counter
“1101”
1D**
“1110”
1E**
“1111”
1F**
ELMOS Semiconductor AG
RETUR
value
enabled
HOLDPROX
4 LSB
8 LSB
disabled
enabled
Select the maximum integrator step size
(see 4.1)
unused
En/Disables an additional touch time ,
which is depending on the signals dynamic. It is used for synchronisation (see 4.4)
enabled
Disables the resetcaused by a detected
WIPE signal when the switch is in togglemode (SWTO=”1”) (see 4.2)
return
counter
value
RETUR switches the data which is send out
via MISO,
disabled
return
command
disabled
enabled
Application Note
21 /39
see section 4.1.3
If enabled the PROX output is held active
(low) as long as an object is inside the
detection area.
QM-No.: 03AN0801E.01
E909.01
Address
“0010”
Data
Hex
“0000”
10**
“0001”
21**
“0010”
22**
“0011”
23**
“0100”
“0111”
24**
27**
“1000”
28**
“1001”
29**
“1010”
2A**
“1011”
2B**
“1100”
2C**
“1101”
2D**
“1110”
2E**
“1111”
2F**
ELMOS Semiconductor AG
Default
Signal
Description
Sets to 3
LSB
4 LSB
-
THZ1
-
Sets to 4
LSB
1st Threshold for proximity
Sets to 4
2nd Threshold for proximity is
LSB
2* THZ1
Sets to 5
LSB
-
sensitive
not
sensitive
unused
Sets to
8 LSB
sensitive
Sets to
16 LSB
Sets to
32 LSB
32 LSB
THZ2
Sets to
64 LSB
Sets to
128 LSB
Minimum dynamic
for touch detection
Sets to
192 LSB
Sets to
256 LSB
not
sensitive
Application Note
QM-No.: 03AN0801E.01
Sets to
512 LSB
22/39
E909.01
Address
“0011”
Address
“0100”
Data
Hex
Default
Signal
“0000”
“0111”
30**
37**
-
-
“1000”
38**
“1001”
39**
“1010”
3A**
“1011”
3B**
(soft)
“1100”
“1111”
3C**
3F**
-
-
Data
Hex
Default
Signal
“0000”
“0111”
40**
47**
-
-
“1000”
48**
65ms
“1001”
49**
130ms
“1010”
4A**
“1011”
4B**
“1100”
4C**
32s
8min
“1101”
4D**
48s
12,5min
“1110”
4E**
“1111”
4F**
ELMOS Semiconductor AG
-
unused
4 LSB/
-1LSB
4 LSB/
-4 LSB
THD1/
THA
130ms
Description
4LSB/
-4LSB
7LSB/
-7LSB
very soft
Velocity and acceleration
threshold for touch.
TOTIM
middle
hard
10LSB/
-10LSB
-
soft
unused
Description
-
130ms
unused
Touch time (holdtime),
constant part of Tvalid
260ms
48s
TIMOV
TOUCHED
60s
No
timeout
Application Note
23 /39
PROX
16min
No
timeout
Duration
of timeout when
system
sate is
TOUCHED
or PROX
QM-No.: 03AN0801E.01
E909.01
Address
“0101”
Data
Hex
Default
Signal
“0000”
50**
-
-
-
“0001”
51**
enabled
OSCON
disabled
“0010”
“0100”
52**
54**
-
-
-
unused
-
unused
“0110”
“1111”
56**
5F**
-
-
Address
Data
Hex
Default
Signal
“0110”
“0000”
“1111”
6***
-
-
ELMOS Semiconductor AG
Description
unused
Switches internal oscillator off
Description
-
Application Note
24 /39
unused
QM-No.: 03AN0801E.01
E909.01
Address
“0111”
Address
“1XXX”
Data
Hex
“0000”
70**
“0001”
71**
“0010”
72**
“0011”
73**
Sets to 3
“0100”
74**
Sets to 0
“0101”
75**
“0110”
76**
“0111”
77**
“1000”
“1001”
78**
79**
“1010”
7A**
“1011”
7B**
“1100”
“1111”
Data
“XXXX”
Default
Signal
Sets to 0
2
2
DYNSTEP
PROXNUM1
-
-
2
PROXNUM2
7C**
7F**
-
-
Hex
Default
Signal
****
Description
-
-
Sets to 1
Sets to 2
Pos./Neg. steps greater than
DYNSTEP are counted up in the
dynamic counters:
sensitive
NEGCNT and POSCNT,
otherwise they are in reset.
not
sensitive
If PROXCNT, which counts the
number of subsequent
Sets to 1
samples that pass the 1st
threshold THZ1, is greater than
Sets to 2
PROXNUM1, than proximity is
detected.
Sets to 3
-
not
sensitive
unused
Sets to 2 If POSCNT or NEGCNT>
PROXNUM2
Sets to 3 proximity is detected
-
sensitive
sensitive
not
sensitive
unused
Description
Test
mode
commands
Don´t use !
Table 2.3: Address decoding
ELMOS Semiconductor AG
Application Note
25 /39
QM-No.: 03AN0801E.01
E909.01
2.3.4 Adjustment of the HALIOS® parameters while using the SPI interface
The parameterization of the IC via SPI by using the parameter commands HICC, HICS, FIXS (see Table 2.3) can
lead to a spontaneous activation of the TOUCH-output. This effect is the result of the sudden change of the DAC
values caused by the adjustment. The TOUCH-output then will remain active for up to 40 seconds until timeout
occurs.
This behaviour only applies to applications that communicate via SPI instead of using the IC stand alone. The
necessary procedure to prevent this effect is described below.
In this case the ENSPI pin of the IC has to be connected to an additional digital output from the external controller as shown in schematic Fig. 2.10. The values of the resistor RD1 and RD2 (values are always equal) are dependant on the supply voltage DVDD. It must be ensured that the maximum possible current through ENSPI is limited
to 1mA.
SCK
MOSI
MISO
use ceramic type condensators (1206) for components C1 and C4
AVSS
TIN
LEDC
C1
10U
R3
TCND3000
10
LEDS
SYI
PROX
SYO
LEDS
TOUCH_b
DVDD
TOUCH_a
ENSPI
SWTO
LDB
ENSPI
R1
R4
500
MOSI
DVSS
RD2
2,7k
C3
47U
VDD
SCK
D2
E909.01A
TIN
C4
10U
AVDD
100K
VDD
Display LED
red
2,7k
GND
RD1
Figure 2.10: Circuit diagram of a freely configurable switch
To parameterize the IC, first, ENSPI must be set low, followed by the two commands ‘a5**’ and ‘a4**’sent via SPI.
Then ENSPI has to be released (set high) again and the parameter commands can be transmitted. The required
timing for this sequence is described in detail in Fig. 2.11. All shown delay times, except the duration, are meant
as minimum values.
�
�����
�
�
���
����
�
����
����
����
����
���
����
����
����
����
����
��������������������
Figure 2.11: Timing diagram of the parameterization sequence
ELMOS Semiconductor AG
Application Note
26/39
QM-No.: 03AN0801E.01
E909.01
2.4 Synchronisation
The synchronisation is done by passing a pulse from one IC to the next. Each IC has an input SYI and an output
SYO. The output SYO is connected to the input SYI of a neighbouring IC E909.01 in a chain of IC E909.01 or connected to its own SYI if there is only one switch. The output SYO is ‚HIGH‘ when an IC E909.01 is performing a
measurement cycle. An E909.01 activates when
1. It is a slave E909.01 and there is a falling edge on the input SYI
2. It is the master E909.01 and the passive time has elapsed.
VDD
VDD
100K
100K
PROX
SYI SYO
PROX
SYI SYO
PROX
SYI SYO
E909.01
E909.01
E909.01
Master
Slaves
Figure 2.12: Example of synchronisation of three E909.01
2.4.1 Definition of master (via resistance 100k)
In a chain of E909.01 there is only one master E909.01. The decision which one functions as master depends on
the output pin SYO. The master E909.01 is defined by a pull-up resistor of 100K on its SYO output. Initially the
digital output of this pin is tristated so the value on the pin depends on whether it is connected to a pull-up or
not.
VDD
100K
SYO_OUT
TRISTATE
EN_SYO
SYO
LOGIC
SYO_READ
Figure 2.13: Decision of master
After the initial power on or a SPI-reset, each E909.01 checks to see if it functions as master or slave. This decision depends on the value of SYO_READ while EN_SYO is ‚LOW‘. The signal EN_SYO controls the tristate buffer,
while it is ‚LOW‘ the pin SYO_OUT is in high resistance state.
The value of EN_SYO is the delayed power-on or SPI reset.
ELMOS Semiconductor AG
Application Note
27/39
QM-No.: 03AN0801E.01
E909.01
2.4.2 Cancelling a touch signal
The touch algorithm consists of mainly three states. In the state APPROX the algorithm has detected an object
and the signal proximity is activated. When the object approaches further with a minimum velocity and stops
on the sensor surface with a minimum acceleration the pre TOUCH-STATE is enabled. When the object remains
calm on the surface for a certain time the TOUCH-STATE is entered.
To avoid the situation where there occurs a touch by two or more switches at the same time a cancel-pretouch
signal is sent over the SYO line to all switches. To ensure that the switch with the highest dynamic responds to
the TOUCH event, the additional touch time with SELDELAY (see table 2.2) should be enabled. This means higher
dynamic causes less delay.
The first switch detecting a TOUCH sends a cancel-pretouch signal on the SYO line. Each switch in turn cancels
its PRETOUCH and sends the cancel-pretouch signal to the next switch. Only the switch that originally detected
the touch can stop this pulse, so the pulse is going round at least once until it reaches the switch which detected
the switch event in the first place. Afterwards all other switches are able to detect another TOUCH event.
The cancel-pretouch signal is a small pulse which is sent after the measurement cycle is finished and a TOUCH
has been detected. To decide whether this signal has been sent or not, the time period is measured in which SYI
is zero after a falling SYI event has occurred. If this time is too short then the switch knows that a TOUCH was
detected by a neighbouring switch and when it is in state PRETOUCH it will cancel this touch event and change
its state to APPROX.
2.4.3 Proximity detection and change of sampling rate
If in a chain of several IC`s E909.01 one of the slaves detects an approaching object it can‘t speed up the sampling rate by itself, as only the master chip is able to do this. Thus all IC`s E909.01 in a synchronised chain are
connected parallel to a pull-up resistor and the master chip can read the common PROX signal to change the
sampling rate (see figure 2.2). To ensure the appropriate functionality the parameter HOLDPROX (see table 2.2)
should be set to ‚0‘ to get the internal PROX = not STANDBY which indicates the sampling rate.
2.5 Analogue parameters
The parameters HICC (High Current Compensation) and HICS (High Current Sender) listed in the address decoding table in paragraph 2.3.3 can be used to set the operating point of the HALIOS® loop. Additionally a self test
can be implemented when using SPI interface. By switching the sending current from low to high a touch should
be detected. The same effect can be achieved by switching the compensation current from high to low.
With FIXS (table 2.2) the LED driver of the sender can be set to regulated (FIXS=0) or fixed mode (FIXS=1). FIXS=1
means that the sending LED is pulsed with a constant current. By setting FIXS=0 the sending current is inversely
controlled to the compensation current. This means that if the compensation current increases, the sending current is decreased by the same relative amount. In this mode the system never saturates and can handle a great
variation in optical reflections.
With G0, G1 the gain of the amplifier is set. It should be set to value that the modulator can differ between single one LSB changes of the DAC. The limiting factor here is the noise of the amplifier which is about 2.7nArms
referred to the input.
With OSCON=0 (see table 2.2) the system can be set to a sleep mode. If this command is sent during a measurement phase the system waits until the measurement has finished before it stops.
ELMOS Semiconductor AG
Application Note
28/39
QM-No.: 03AN0801E.01
E909.01
3 Application diagrams
3.1 Application diagram of a switch without SPI
The simplest configuration consists of one switch IC E909.01 as a single switch without SPI interface. The corresponding circuit diagram is shown in figure 3.1. The touch and the proximity signal are indicated with two LEDs.
With the pin SWTO one is able to define whether the touch output should be activated only during the time the
touch event is detected (touch mode) or if the touch output should toggle its state with each Touch event (toggle mode). The following voltages must be applied to select the corresponding mode:
Touch mode: SWTO = VDD
Toggle mode: SWTO = GND
LEDS
C1
10U
SYI
DVSS
SYO
LEDS
TOUCH_b
DVDD
TOUCH_a
ENSPI
SWTO
R2
R1
500
R4
500
PROX
Touch LED
C3
47U
VDD
R3
TCND3000
10
LEDC
BEEPER
Proximity LED
D1
AVSS
SCK
MOSI
D2
TIN
C4
10U
AVDD
100K
TIN
E909.01A
VDD
GND
Figure 3.12: Circuit diagram of a single switch without SPI interface
3.2 How to increase the detection range
The sensitivity or the detection range is proportional to the sending current (pin LEDS) and inverse proportional
to the compensation current (pin LEDC). The IC E909.01 allows to increase the sensitivity by internally influencing the range of the LED currents with SPI commands. With the SPI command “0D” it is possible to increase the
sending current range from 10mA to 20mA. By using the SPI command “0A” the compensation current range is
reduced from 2mA to 1mA. The two commands allow to improve the sensitivity of the sensor by a factor of four.
With the external drivers shown in Figure 3.2 it is possible to increase the currents to larger values than it is possible with the internal drivers. With the emitter resistor of PNP2 the compensation current can be adjusted and
it is possible to adapt the LED current for both channels independently of each other. If the sensitivity is enlarged
one must pay attention to avoid saturation of the measurement signal. Should this happen, the stray-light from
the sending LED to the photodiode must be reduced by using an optical blocking layer between the translucent
surface and the TCND3000. This includes also the air-gap between both lenses of the TCND3000. Please refer to
chapter 1.5.
ELMOS Semiconductor AG
Application Note
29/39
QM-No.: 03AN0801E.01
BC857
PNP2
1K
R15
R14
2,2K
E909.01
BC817
NPN2
SCK
R17
R16
1,8K
2,2K
MOSI
MISO
TIN
TIN
AVSS
LEDC
C1
10U
10
TCND3000
R3
LEDS
SYI
R1
R4
500
100K
SPI signals
LDB
Proximity LED
PROX
DVSS
SYO
LEDS
TOUCH_b
DVDD
TOUCH_a
ENSPI
SWTO
RD2
0
C3
47U
VDD
SCK
MOSI
D2
C3
47U
C4
100N
AVDD
E9 0 9 .0 1A
VDD
R12
680
R13
270
BC817
NPN1
R11
150
27
BC857
PNP1
R10
GND
Figure 3.13: Control of the optomodule TCND 3000 with external LED drivers
Another possibility to avoid saturation of the measurement signal is to regulate both the sending current and
the compensation current. In normal mode after power up only the compensation current is regulated (FIXS is
enabled). By using the SPI command “0E” (FIXS is disabled) the sending LED current is regulated according to the
equation
I SEND = I R ANGE_SEND * (1 – Loopvalue / 1023)
while the compensation current is regulated according the following equation
I COMP = I RANGE_COMP * Loopvalue / 1023.
In this case, however, the sensitivity is decreased when the measurement signal approaches the limit of the
range in order to avoid saturation. Thus the most effective way to avoid saturation in a system with high sensitivity is to reduce the stray light as described above.
ELMOS Semiconductor AG
Application Note
30/39
QM-No.: 03AN0801E.01
E909.01
3.3 Cascading of optical switches
Several switches can build a group by using the synchronisation bus. This has several advantages.
First, one proximity function for all switches in the group can be realized. This makes it possible to illuminate selected parts of the control panel and define groups of functions. The second advantage is the possibility to avoid
unwanted operation by cancelling parasitic touch events. If one switch detects a touch event all other switches
are disabled for a short time. A third advantage is that the measurement phase of switches among one group is
activated sequentially. This allows switches to be located close together avoiding disturbances if light from one
switch is reflected to another switch. The schematic below shows a group of two switches which are connected
with the synchronisation bus.
C1
10U
R3
TCND3000
10
LEDC
LEDS
R2
R4
500
R1
500
Shared Proximity LED for both switches
PROX
DVSS
SYO
LEDS
TOUCH_b
DVDD
TOUCH_a
ENSPI
SWTO
Touch LED A
Master (with pull up resistor at pin SYO)
C3
47U
VDD
SYI
D1
AVSS
SCK
MOSI
D2
TIN
C4
10U
AVDD
100K
TIN
E909.01A
VDD
GND
TIN
C2
10U
AVSS
LEDS
C5
TCND3000
10U
LEDC
R5
SCK
500
AVDD
MOSI
SYI
PROX
DVSS
SYO
LEDS
TOUCH_b
DVDD
TOUCH_a
ENSPI
SWTO
D3
TIN
E909.01A
R6
10
VDD
Touch LED B
Slave (with pull up resistor at pin SYO)
Figure 3.14: Circuit diagram of two synchronised switches
The synchronisation bus is activated by connecting the SYO pin of one switch to the SYI pin of the next switch.
The last switch is then connected to the first switch building a closed loop. One switch in this loop is defined as
the master by using a pull-up resistor at its SYO pin and connecting all PROX output pins with one pull-up resistor. If one switch in the group detects an approaching object all other switches are switched from standby mode
to active mode. The master synchronizes the sampling rate, the “pretouch” time (parameter TOTIM in table 2.2)
and the global timeout (parameter TIMOV in table 2.2) of all switches in the group.
Figure 3.4 shows how parasitic touches are cancelled. If several switches are in the “pretouch” phase at the same
time the switch that leaves the “pretouch” time first cancels all other “pretouch” phases that are active at this
time. This is done by sending a pulse on the synchronisation bus from one switch to the next. If several switches
have activated their “pretouch” phase during the same measurement cycle they will leave their “pretouch” phase
at the same time. In this case the order in the chain of the synchronisation bus determines which switch will
have a valid touch. This means the first switch seen from the front of the chain will accept the touch.
ELMOS Semiconductor AG
Application Note
31 /39
QM-No.: 03AN0801E.01
E909.01
Parameter: TOTIM
Switch 1:
Pretouch time switch 1
Switch 2:
Switch 3:
Touch accepted
Pretouch time switch 2
Touch cancelled
Pretouch time switch 3
Switch 4:
Pretouch time switch 4
Touch accepted
Time
Figure 3.15: Prioritisation of touch events by disabling other touches during the “Pretouch” time
It is also possible to prioritise the switch with the largest signal amplitude to accept the touch. With the parameter SELDELAY (parameter SELDELAY is described in table 2.2) this option can be enabled. In this case the constant
“pretouch” time is extended by a variable part, which is proportional to the signal amplitude. If now several
switches are entering the “pretouch” phase during the same measurement cycle the switch with the largest signal amplitude will win and activate its touch output.
3.4 Reference Design
The circuit diagram (figure 3.5) below shows an application where the SPI interface is not used in normal operation. It is, however, possible to activate the SPI interface for test purpose by removing the components RD1, RD3,
RD4, RD5, RD6 and inserting component RD2. In the case of an activated SPI interface the Touch output is not active any more.
Due to the synchronous demodulation principle of the HALIOS® regulation loop asynchronous disturbances
outside the modulation frequency band are not critical and do not disturb the measurement. Only synchronous
electrical and optical disturbances can influence the measurement. Thus it is important to avoid electrical coupling of the modulation frequency to the photodiode input and the analogue supply of the E909.01 IC. This can
be avoided by shielding the photodiode connection line with analogue ground, which should be designed like
a grounded coplanar line. Additionally the analogue supply should be decoupled with a lowpass of first order
given in the example by the components R3 and C4.
The ground connection between TCND3000 and E909.01 should be of low resistance type with a ground plane.
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QM-No.: 03AN0801E.01
E909.01
SCK
MOSI
MISO
LDB
VDD
use ceramic type condensators for components C1 and C4
0
C1
10U
10
TCND3000
R3
LEDC
LEDS
RD2
0
C3
47U
VDD
GND
MOSI
SYI
RD4
R2
R1
500
R4
500
100K
0
BEEPER
Proximity LED
PROX
DVSS
SYO
LEDS
TOUCH_b
DVDD
TOUCH_a
ENSPI
SWTO
Touch LED
D1
AVSS
SCK
D2
TIN
C4
10U
AVDD
E909.01A
RD5
TIN
0
0
RD6
RD3
RD1
0
do not insert component RD2 in case SPI is not used!
for test purpose the sPI interface can be activated by removing
the components RD1, RD3, RD4, RD5, RD6 and inserting component RD2.
Figure 3.16: Schematic diagram of test circuit with SPI interface
Figure 3.17: PCB Layout of test circuit (top side)
ELMOS Semiconductor AG
Application Note
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QM-No.: 03AN0801E.01
E909.01
Figure 3.18: PCB Layout of test circuit (bottom side)
4 Related Documents
Dokument-No.: 03SP0277E.XX
ELMOS Semiconductor AG
Specification E909.01
Application Note
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[1]
QM-No.: 03AN0801E.01
E909.01
5 Record of Revisions
Chapter
Rev.
3.3
1
-
1
Change and Reason for Change
Date
Released
Figure 3.14
03.04.2006
RME/ZOE
page 39 removed - page 5 moved to page 38
03.04.2006
RME/ZOE
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QM-No.: 03AN0801E.01
E909.01
Contents
System Comparison....................................................................................................................................................................................2
SOP16 Package Outline and Description..............................................................................................................................................4
TSSOP16 Package Outline and Description.........................................................................................................................................4
1 Optics ...........................................................................................................................................................................................................5
1.1 Optical Operation Principle ..........................................................................................................................................................5
1.2 Optical and Geometrical Design ...............................................................................................................................................8
1.3 Surface materials and mechanical set-up .............................................................................................................................11
1.4 Design Rules ...................................................................................................................................................................................12
1.5 Advanced configuration .............................................................................................................................................................13
2 Working Principle ASIC .........................................................................................................................................................................15
2.1 Block Diagram ................................................................................................................................................................................15
2.2 Overview Basic Funktions .........................................................................................................................................................16
2.2.1 Syncronisation .....................................................................................................................................................................16
2.2.2 Active and Stand-by Operation Mode........................................................................................................................16
2.2.3 Detection Algorithms........................................................................................................................................................17
2.3 SPI Interface....................................................................................................................................................................................17
2.3.1 SPI Transmission...................................................................................................................................................................18
2.3.2 MISO Line...............................................................................................................................................................................18
2.3.3 Address decoding...............................................................................................................................................................20
2.3.4 Adjustment of the HALIOS® parameters while using the SPI interface...........................................................26
2.4 Synchronisation............................................................................................................................................................................27
2.4.1 Definition of master (via resistance 100k)..................................................................................................................27
2.4.2 Cancelling a touch signal................................................................................................................................................28
2.4.3 Proximity detection and change of sampling rate.................................................................................................28
2.5 Analogue parameters.................................................................................................................................................................28
3 Application diagrams............................................................................................................................................................................29
3.1 Application diagrams of a switch without SPI....................................................................................................................29
3.2 How to increase the detection range....................................................................................................................................29
3.3 Cascading of optical switches...................................................................................................................................................31
3.4 Reference Design..........................................................................................................................................................................32
4 Related Documents...............................................................................................................................................................................34
5 Record of Revision..................................................................................................................................................................................35
Contents.......................................................................................................................................................................................................36
List of Figures......................................................................................................................................................................................37
List of Tables........................................................................................................................................................................................37
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QM-No.: 03AN0801E.01
E909.01
List of Figures
Figure 1.1: Diffusion of human finger.....................................................................................................................................................5
Figure 1.2: Diffusion of some clothes....................................................................................................................................................6
Figure 1.3: Schematic setup with TCND 3000.....................................................................................................................................7
Figure 1.4: Basic arrangement using TCND 3000 module supplied by VISHAY®....................................................................9
Figure 1.5: Photocurrent caused by reflection vs. distance. (cf. VISHAY® datasheet figure 5)...........................................10
Figure 1.6: Current mirror circuit (shown values are a very good starting point)..................................................................13
Figure 1.7: Introduction of optical shielding...................................................................................................................................... 14
Figure 2.8: Block Diagram E909.01........................................................................................................................................................15
Figure 2.9: Example of a correct data transmission, command h2200....................................................................................18
Figure 2.10: Circuit diagram of a freely configurable switch.......................................................................................................26
Figure 2.11: Timing diagram of the parameterization sequence................................................................................................26
Figure 2.12: Example of synchronisation of three E909.01 IC`s...................................................................................................27
Figure 2.13: Decision of master..............................................................................................................................................................27
Figure 3.12: Circuit diagram of a single switch without SPI interface.......................................................................................29
Figure 3.13: Control of the optomodule TCND 3000 with external LED drivers....................................................................30
Figure 3.14: Circuit diagram of two synchronised switches..........................................................................................................31
Figure 3.15: Prioritisation of touch events by disabling other touches during the “Pretouch” time...............................32
Figure 3.16: Schematic diagram of test circuit with SPI interface..............................................................................................33
Figure 3.17: PCB Layout of test circuit (top side)...............................................................................................................................33
Figure 3.18: PCB Layout of test circuit (bottom side).....................................................................................................................34
List of Tables
Table 1.1: Samples of tested materials..................................................................................................................................................11
Table 2.2.........................................................................................................................................................................................................18
Table 2.3: Address decoding...................................................................................................................................................................25
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QM-No.: 03AN0801E.01
E909.01
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