Scope AVDD VDDC NRST. reset clock test. CPU core 16 bit. multiply HALIOS. control. watchdog. digital/ analog IRQ. control. timer

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1 Designing capacitive Sensors with E99.6 Sensor IC AN 1 Features Scope Sensor IC based on HALIOS technology up to 4 sending channels, 1 compensation channel and 1 receiver input for different HALIOS applications 16 bit micro controller 'EL16' with debug interface up to 1.5Kx18 (3KByte) SRAM including 2 bit parity per 16 bit word and byte write support up to 3Kx22 (6KByte) FLASH including 6 bit CRC checksum per 16 bit word SPI and I²C communication interface SCI interface incl. LIN support Watchdog, 32 bit timer, up to 8 GPIOs Multiply unit Operating temperature range -4 C to 85 C Applications Capacitive input devices Liquid spray detection Liquid level detection Capacitve Proximity sensors This application note provides information about how to design capacitive sensors with the Sensor IC E99.6 and gives examples of different measure ment configurations and the corres ponding sensor behaviour. General Description The function principle is based on a closed loop controlled compensation technique and allows to reach a large detection range by sensing capacitive changes in the sub-femtofarad region. At the same time the sensor principle allows to suppress EM disturbances even at the sensor's measurement frequency. This is essential for designing products with high sensitivity. The frontend alalogue circuitry and the modulator can be configured with software allowing to realise different applications. This application note describes sensor applications based on measuring the coupling capacitance of two electrodes in a charge amplifier configuration. AVDD VDDC NRST TMODE KA AMP_KA - reset clock test AMP_AN AN - CPU core 16 bit J T A G RAM Flash TM TM1 VPP LED1 LED2 LED3 LED4 LEDC HALIOS control digital/ analog multiply watchdog IRQ control timer SPI interface LIN SCI GPIO interface I 2 C interface MISO MOSI SCK CS RX TX SDA SCL 8 GPIO VDDIO SDA SCL E99.6 Figure 1: Typical application diagram ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

2 AN 1 1 Block Diagram AVDD VDDC NRST TMODE KA AMP_KA - reset clock test AMP_AN AN - CPU core 16 bit J T A G RAM Flash TM TM1 VPP LED1 MISO LED2 LED3 LED4 LEDC HALIOS control digital/ analog multiply watchdog IRQ control timer SPI interface LIN SCI GPIO interface I 2 C interface MOSI SCK CS RX TX SDA SCL 8 GPIO VDDIO SDA SCL E99.6 Figure 2: Block diagram 2 Operating Principle The function principle of the capacitive sensor is based on a closed loop controlled compensation technique. This technique is similar to the HALIOS measurement principle, which is used also for optical and inductive sensors. Dependent on the application of the capacitve sensor there are different useful measurement configurations. If the capacitance to be measured has a large sensitivity to ground the measurement should be done in a ground related configuration. In this case the stray capacitance of one electrode to ground is measured. The frontend amplifier should be configured as transimpedance amplier, then the measurement is based on sensing a change in an RC time constant. To detect for example water it is more useful to measure the coupling capacitance beween two electrodes. This can be done in a ground free measurement based on charge conservation using a charge amplifier. One advantage of this measurement is that the parasitic capacitance of both electrodes to ground does not influence the measurement, in particular, the sensitivity is not reduced. Further it is possible to shield the wiring con nect ions of the sensor capacitances allowing a measurement which cannot be disturbed by touching the electrode wiring or the housing. The symmetrical analogue input together with the closed loop controlled modulation sources allows to suppress EM noise even at the sensor's measurement frequency. This application note describes the ground free configuration measurement with a charge amplifier, where the coupling capacitance between two electrodes is measured in differential and absolute manner. ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

3 AN Differentially capacitive sensor The block diagram below illustrates the functioning of the differential ground free capacitive sensor. Two clock signals MODS and MODC, which can be modulated in the amplitude, are fed into the sensor capacitances CM1 and CM2. Each of both capacitances is connected to a charge amplifier. AVDD VDDC MODS CM1 KA AMP_KA AMP_AN - MODC CM2 AN - Sensorcapacitances LED1 Clock LED2 Result LED3 I A =I RNG_A (1-x)I OFF_A LED4 LEDC I B =I RNG_B xi OFF_B HALIOS control digital/ analog Figure 3: Block diagram of the sensor for differential measurements of CM1 to CM2 In a second amplifier stage the outputs of the charge amplifiers are subtracted from one another. The amplitude of the signal AMPOUT is then minimized to zero in a closed loop regulation process by demodulation and integration with a regulator which generates amplitude modulated clock signals at the nodes MODS and MODC to stimulate the sensor capacitances. The measurement result is represented by the output Result of the regulator and is related to the capacitances CM1 and CM2 by the following formula: Result= C M2 C M1 C M2 equation 1.1 This formula is valid, if the offset current I OFF_A and I OFF_B shown in the blockdiagram of figure 3 is zero and the current range I RNG_A and I RNG_B is equal. If C M1 = C dc and C M2 = C the result can be expressed as follows using the condition of dc << C: Result=.5 dc 2 C equation 1.2 ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

4 AN 1 By using the Offset current the sensitivity of the measurement can be increased. The current I RNG_A and I RNG_B are defining the current range of the regulated part of the modulation current and the offset currents I OFF_A and I OFF_B are defining a part of the modulation current with a fixed amplitude. This is shown in the blockdiagram of figure 3 where the formula for current I A and current I B are described. By using equal offset currents for A and B current part I OFF_A = I OFF_B = I OFF and using also equal current ranges I RNG_A = I RNG_B = I RNG the following formula can be applied: Result = C M2 If the capacitances C M2 is again equal C and C M1 is expressed as C dc the following formula follows from equation 1.3 using again dc << C: Result =.5 1 I OFF I RNG C M2 C M1 C M1 C M2 equation 1.3 I OFF I RNG equation 1.4 By comparing equation 1.2 with 1.4 it can be seen that the sensitivity is increased by a factor of (1 I OFF / I RNG ), when the offset currents are used. dc 2C A timing diagram of the sensor function is shown in figure 4. At the beginning the regulation loop is in the settled state because the output of the demodulator DEMOD is zero. The amplitude of both modulation signals MODS and MODC are equal which corresponds to the equal sized capacitances CM1 and CM2. At time t = 6µs the capacitance CM1 is reduced by a factor of two. This leads to an reduction in the amplitude at the output OUTM of the first charge amplifier. Since the outputs of both charge amplifiers are not equal in size any more the output signal at the node AMPOUT has a certain non zero amplitude. The demodulator produces an error signal DEMOD which leads to a change at the integrator output until the error signal is again reduced to zero. By using the equation 1.1 the output of the integrator RESULT changes from.5 to.66 if the ratio of CM1/CM2 changes from 1 to.5. CM1/CM2 1.5 CM1/CM2.5 Mods Modc Outm Outp Ampout Demod.5.7 Result.6.5 t / us Figure 4: Timing diagram of the capacitive HALIOS sensor for ratiometric measurement of CM1 to CM2 ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

5 AN Reduction of EMV noise If EM noise is present an error current may be injected into the sensor electrodes producing an disturbance on the virtual ground node of both amplifiers. This leads to an error signal on both charge amplifier outputs OUTM and OUTP as shown in figure 5. Due to the common mode character of this noise signal the error is cancelled out at the output of the second opamp stage. To have a good noise reduction the sensor electrodes of both capacitances should be symmetrical in order to insure that the same error signal is injected into both amplifier inputs. The advantage of this noise reduction feature is that even if the EM noise has the same frequency than the sensor the measurement is not disturbed. This is an important feature for capacitive sensors because the electrodes cannot be shielded very good due to the fact that the electromagnetic field must be radiated out into the environment to be influenceable by the measurement object. With an enlargment in the sensitivity of the sensor electrodes normally the sensitivity to EM noise is also enlarged. Therefor this feature is very important in deploying capacitive sensors with high sensitivity. CM1/CM2 1.5 CM1/CM2.5 Mods Modc EM noise Outm Outp Ampout Result.6.5 t / us Figure 5: Timing diagram of the capacitive HALIOS sensor for ratiometric measurement of CM1 to CM2 with EM noise ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

6 AN Capacitive sensor for absolute measurements To be able to measure common mode changes of the sensor capacitances CM1 and CM2 another measurement setup than described in former chapter is necessary. The block diagram below illustrates the functioning of the ground free capacitive sensor for absolute measurements. In contrast to the differentially sensor CM1 and CM2 are not measured simultaneously. First sensorbridge 1 is measured by activating the modulator signals MODS1 and MODC1, meanwhile the modulators of sensorbridge 2 are stopped. Thus the capacitor CM1 is measured relatively to the refence capacitance CREF1. Again the amplitude of the signal AMPOUT is minimized to zero by regulating the amplitude of the modulation clock at the nodes MODS1 and MODC1 in a closed loop process. In this measurement configuration the zero signal is achieved at the node KA by using simply a short to connect both branches of the sensorbridge 1. Because the signal currents are added at the node KA it needs modulation clock signals with 18 degree phaseshift to achieve the signal cancellation. MODS1 CM1 Sensorbridge 1 MODC1 CREF1 AVDD VDDC MODS2 CM2 KA AMP_KA AMP_AN - MODC2 CREF2 AN - Sensorbridge 2 LED1 Clock LED2 Result LED3 I A =I RNG_A (1-x)I OFF_A I B =I RNG_B xi OFF_B LED4 LEDC HALIOS control digital/ analog Figure 6: Block diagram of the sensor for absolute measurements of CM1 to CM2 In contrast to this the differentially capacitive sensor described in the former chapter used clock signals with no phaseshift, because the signal cancellation is achieved with an OPAMP producing the difference between the signals. The corresponding timing diagram for this measurement configuration is shown in figure 7. Due to the passive summation with a simple short the clock signals MODS1 and MODC1 have now 18 degree phaseshift and at the output of the charge amplifier a zero signal appears if the regulation loop is settled. This is the case at the beginning of the measurement until at T=6µs. Then the capacitance CM1 is changed by a certain amount and an non zero clock signal appears at the output OUTM of the first charge amplifier. The demodulator produces an error signal and the regulator changes the amplitude of the modulation signals until the error signal disappeares and the settled state is reached again. ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

7 AN 1 CM1/CREF CM1/CREF1 Mods1 Modc Outp Outm Ampout Demod.5.7 Result.6.5 t / us Figure 7: Timing diagram of the capacitive HALIOS sensor for ratiometric measurement of CM1 to CREF1 The mechanism of EM noise suppression is similar to the difference sensor and is shown for the case of the absolute sensor in figure 8. The function principle is based on that both electrodes CM1 and CM2 are influenced by EM noise in the same amount. Although the modulators of the sensorbridge 2 are stopped, the corresponding input amplifier at node AN is active. Figure 8 shows the disturbances of both sensor bridges at the outputs OUTM and OUTP of the two charge amplifiers. As already shown for the differentially capacitve sensor the second stage OPAMP suppresses the noise by its common mode rejection ratio. CM1/CREF1 1.5 CM1/CREF1.5 Mods1 Modc EM noise Outp Outm Ampout Result.6.5 t / us Figure 8: Timing diagram of the capacitive HALIOS sensor for ratiometric measurement of CM1 to CREF1 with EM noise ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

8 AN 1 By using the amplitude information B for the MODS1 modulator and the inverted amplitude A for the MODC1 modulator the measurement result can be expressed by the following formula: Result = C M1 C REF1 C M1 equation 2.1 The capacitance CM1 is now measured in relation to a reference capacitance which is fixed in its value and is not influenced by the environment like the capacitances CM1 and CM2. This is the reason why this configuration is called absolute measurement, although it is a ratiometric measurement of CM1 to CREF1. If the parasitic capaci tances shown in figure 9 are taken into account the transfer function is expressed by equation 2.2: Result= C M1 C KS1 C REF1 C KC1 C M1 C KS1 equation 2.2 The effect of the parasitic capacitance CKS1 is that the sensitivity may be reduced. It depends on how the object to be detected influences both cpacitances CKS1 and CM1. In order to reduce this effect the parasitic capacitances should be as low as possible. CKC1 can be suppressed easily by shielding. CKS1 originates by direct cross coupling between the electrodes. Thus this capacitance cannot be avoided, but it should be kept small in relation to CM1 by appropiate design of the electrode layout. MODC1 CREF1 Sensorbridge 1 MODS1 CM1 CKC2 CKS2 CKC1 CKS1 Sensorbridge 2 MODS2 CM2 MODC2 CREF2 Figure 9: Parasitic capacitances which influence the measurement The capacitance CM2 is measured by activating the modulators MODS2 and MODC2, while the MODS1and MODC1 modulators are stopped. As before the amplitude information A is asigned to the reference capacitor CREF2 and amplitude information B is asigned to the measurement electrode CM2. Then the measurement result is as follows: C M2 C KS2 Result= C REF2 C KC2 C M2 C KS2 equation 2.3 ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

9 AN 1 3 Programming the measurement and the application The Sensor IC has an embedded 16bit microcontroler to controle the measurements and to implement application software. In the following paragraphs it is described how to configure the measurements with special function registers. Further firmware software and PC software which simplifies the work is described. 3.1 Controlling the measurement with special function registers Generally the automated measurement cycle is started with the bit HALMEAS in the register Measurement configuration. For each measurement the hardware is activated for 25 modulator clock cycles. Then the 1 Bit measurement result is available in the register Measurement result. When the cycle is finished the bit HALMEAS is cleared and an interrupt appears if the interrupt is enabled. In the following example it is shown how to configure the E99.6 IC to do the differentially capacitive measurement described in chapter 2.1. The following special function registers must be configured before starting the measurement: 1)Register: Measurement Configuration 2)Register: Preamplifier Configurations 3)Register: Measurement Configuration HALIOS clock 4)Register: Current Configuration A 5)Register: Current Configuration B 6)Register: Measurement Configuration 7)Register: Start Value Counter 8)wait 1µs until the charge amplifier has settled 9)Register: Preamplifier Configurations After the configuration of the registers is done the measurement can be started and the the result can be fetched when the measurement is finished: 1)Setting the bit HALMEAS in register Measurement configuration starts the measurement 11)Wait on that the bit HALMEAS is cleared to indicate the measurement is finished. 12)Fetch the measurement result from the registers Counter Value and Mean Value 13)To have the correct start value for the next measurement with this configuration the last counter steps size and the counter start value should be saved from register Start Value Counter. On the next pages the configuration of the SFR register before starting the measurement is described. Step 1): To switch the analog part on after power down the bit 12 must be set to one. ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

10 AN 1 Register Measurement Configuration (x2): Value = x524h MSB Content Reset value Internal access External access Table 1: Measurement Configuration R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W Bit Value Bit Description 12 : AON: Control of analogue part ('' = off, '1' = on) LSB Step 2): To insure the correct operating point of the charge amplifier a circuit called capacitive gyrator is used. This circuit must be activated with the bits 9 and 1. The amplification factor of the third stage amplifier is switched to 64 by setting bit 8 to 1. In order to have a short settling time after switching on the analog part after power down the first stage amps should be configured as transimpedance amplifiers with the feedback resistor activated. This is done during step 2) by writing to the bits and 1. In step 9) these bits must be set to 1 in order to deactivate the feedback resitors to get the charge amplifier configuration for the capacitive measurement. Register Preamplifier Configuration (x12): Value = x83 MSB Content Reset value Internal access External access R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W Bit Value Bit Description 1 : Select between optical and capacitive gyrator at AN input: ('' = optical, '1' = capacitive) Note: not available in version 1 and version 3 9 : Select between optical and capacitive gyrator at KA input: ('' = optical, '1' = capacitive) Note: not available in version 1 and version 3 8:7 : Select amplification of 3. Stage AMP "1" 4; "1" 64; "11" 16; "" : 1. stage amplifier AN input: RF Feedback resistor deactivation ('' = on, '1' = off) : 1. stage amplifier KA input: RF Feedback resistor deactivation ('' = on, '1' = off) LSB Table 2: Preamplifier Configuration Step 3): After this the clock polarity of the modulators must be defined. If the default values are used A current outputs and B current outputs are assigned inverted clock signals. In our example of the differentially capacitive sensor non inverted clock phases are needed. To do this the clock signal of the A current output LED3 in this example must be inverted. This is done by setting the bit 2 of the following register: ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

11 AN 1 Register Measurement Configuration HALIOS Clock (x4): Value = x4 MSB Content Reset value Internal access R R R R R R R R R R R R/W R/W R/W R/W R/W External access R R R R R R R R R R R R/W R/W R/W R/W R/W Bit Value 1 1 Bit Description 4 : Polarity of LEDC Modulator clock ('' = normal, '1' = inverted) 3 : Polarity of LED4 Modulator clock ('' = normal, '1' = inverted) Note: not available in version 1 and version 2 2 : Polarity of LED3 Modulator clock ('' = normal, '1' = inverted) Note: not available in version 1 and version 2 1 : Polarity of LED2 Modulator clock ('' = normal, '1' = inverted) : Polarity of LED1 Modulator clock ('' = normal, '1' = inverted) Table 3: Measurement Configuration HALIOS Clock LSB Step 4) and 5): Next the current values for the A and B current sources are adjusted. If the sensor electrodes are symmetrically then the current values for both modulators can be assigned to the same value. In our example we choose medium sensitivity by using for the offset current 5mA and for the regulated current part we choose a range of 625µA. This leads to an amplification factor of I OFF / I RNG = 8. Register Current Configuration Phase A (x6): Value = x82 MSB Content : : Reset value Internal access R R R R R R R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W External access R R R R R R R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W Bit Value Bit Description Table 4: Current Configuration Phase A 9:5 : OFF: Offset current for A current sources. 4: : RNG: Range of regulated part of A current sources. LSB ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

12 AN 1 Register Current Configuration Phase B (x8): Value = x82 MSB Content : : Reset value Internal access R R R R R R R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W External access R R R R R R R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W Bit Value Bit Description Table 5: Current Configuration Phase B 9:5 : OFF: Offset current for B current sources. 4: : RNG: Range of regulated part of B current sources LSB Step 6): Before the measurement can be started the current source outputs LED2 and LED3 which should be used for the measurement must be activated. This is done by assigning the current amplitude information I A to one modulator and I B to the other modulator. The block diagram in figure 3 shows that this is done by defining the switches between modulator input and the functional unit where the current amplitude I A and I b are generated. In our case we assign LED2 to I B current and LED3 is assigned to I A current. Additionally the Bit which switches the analog part on should be kept activated. Register Measurement Configuration (x2): Value = x524h MSB Content Reset value Internal access External access Table 6: Measurement Configuration R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W Bit Value Bit Description 12 : AON: Control of analogue part ('' = off, '1' = on) 5 : LED 3 A: Decides if LED is active for the measurement ('' = off, '1' = on) 2 : LED 2 B: Decides if LED is active for the measurement ('' = off, '1' = on) LSB ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

13 AN Using firmware software to implement the application To simplify the usage of the E99.6 Sensor IC a firmware software package can be used. The structure and the relation to hardware and user software is shown in figure 1. The API of the firmware library makes available the HALIOS sensor function and the peripherals of the E99.6A for the application software engineer. Further more a communication protocol is implemented to afford the communication between the visualisation PC software called HACO and the E99.6A firmware. USER Application Software FIRMWARE API store HOST I²C 2 C SPI HALIOS measurement paramgetresult paramget/setvalue RAM SFR USERSPACE deviceflash/restoresfr I 2 C/SPI-handling (SLAVE) FLASH parameter CODE E99.6 Sensor IC hardware HALIOS Module I 2 C Module SPI Module GPIO Module TIMER Module RAM FLASH Figure 1: Layer view of E99.6 hardware, firmware software and user application software The flow chart of the main.c program of the firmware is shown in figure 11. After initialization of the E99.6 IC the different measurement configurations which should be used during the periodic measurement are defined in the SFR and users pace. The measurement of all defined configurations is activated with one function call. The result of the measurement can now be processed by the user application code. In order to reduce the current consumption the device can be put into sleep mode after the sensor data have been processed. Each measurement takes about 2µs. If two measurements are defined this takes about 5µs together with the warm up time after switching on the analog part from sleep mode. The advantage of using the wake up timer is a reduction in the current consumption of the IC. By using a wake up time of 1ms the power consumption can be reduced by a factor of about 2. For detailed information to the firmware please refer to the related documents. ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

14 AN 1 Initialize E99.6 Initialize SFR Userspace Watchdog Reset paramchecksfr Firmware functions Measurement User Application Code devicewaitfortimer Figure 11: Layer view of E99.6 hardware, firmware software and user application software 3.3 Using the PC software HAKO The HAKO software is a PC program which allows to configure the E99.6 IC for different measure ments and the results can be visualized graphically. The software can be connected via USB or serial port to the E99.6 EVA board or the user hardware. Figure 12: HAKO is a PC software which allows to configure different measurements and to visualize the measurement results. ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

15 AN 1 Figure 12 shows three windows of the software. The window on the left side allows to select different measurement configurations named LOOP1 to LOOP12. The selected measurements are repeated periodically. The window on the right side called Configuration E99.6A allows to define each of the selected measurement configurations. In this example the measurement called LOOP4 is configured and the output LED2 is assigned to B current and LED3 is assigned to A current with the pull down menu. Further the B current source is switched to 9,6875mA offset current and the regulated part is set to 2.5mA current range. For the A current source 1mA is selected for offset current and the range of the regulated part is also put to 2.5mA. Now the output ports and the modulator currents are defined. Below the area with the pull down menus several rows with radio buttons can be found. The first row allows to select the clock polarity for LED1 to LED5. As explained in chapter 2.4 the clock of the Phase A current must be inverted in our example of the differentially sensor. The next two rows of radio buttons allow to configure the preamplifier. To use the first stage amps as charge amplifier the internal feedback resistor must be switched off with the first two radio buttons. Additionally the gyrator for the capacitive measurement must be activated by turning on the two radio buttons below in the next row. On the right side the amplification factor of the third stage amp can be adjusted. A good choice is 16 or 64. For a detailed description of the HAKO software please refer to the related documents. ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

16 AN 1 4 Application diagram ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

17 AN 1 Contents 1 Block Diagram Operating Principle Differentially capacitive sensor Reduction of EMV noise Capacitive sensor for absolute measurements Programming the measurement and the application Controlling the measurement with special function registers Using firmware software to implement the application Using the PC software HAKO Application diagram List of Figures Figure 1: Typical application diagram Figure 2: Block diagram Figure 3: Block diagram of the sensor for differential measurements of CM1 to CM Figure 4: Timing diagram of the capacitive HALIOS sensor for ratiometric measurement of CM1 to CM Figure 5: Timing diagram of the capacitive HALIOS sensor for ratiometric measurement of CM1 to CM2 with EM noise... 5 Figure 6: Block diagram of the sensor for absolute measurements of CM1 to CM Figure 7: Timing diagram of the capacitive HALIOS sensor for ratiometric measurement of CM1 to CREF Figure 8: Timing diagram of the capacitive HALIOS sensor for ratiometric measurement of CM1 to CREF1 with EM noise... 7 Figure 9: Parasitic capacitances which influence the measurement Figure 1: Layer view of E99.6 hardware, firmware software and user application software Figure 11: Layer view of E99.6 hardware, firmware software and user application software Figure 12: HAKO is a PC software which allows to configure different measurements and to visualize the measurement results ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

18 AN 1 WARNING Life Support Applications Policy ELMOS Semiconductor AG is continually working to improve the quality and reliability of its products. Nevertheless, semiconductor devices in general can malfunction or fail due to their inherent electrical sensitivity and vulnerability to physical stress. It is the responsibility of the buyer, when utilizing ELMOS Semiconductor AG products, to observe standards of safety, and to avoid situations in which malfunction or failure of an ELMOS Semiconductor AG Product could cause loss of human life, body injury or damage to property. In development your designs, please ensure that ELMOS Semiconductor AG products are used within specified operating ranges as set forth in the most recent product specifications. General Disclaimer Information furnished by ELMOS Semiconductor AG is believed to be accurate and reliable. However, no responsibility is assumed by ELMOS Semiconductor AG for its use, nor for any infringements of patents or other rights of third parties, which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of ELMOS Semiconductor AG. ELMOS Semiconductor AG reserves the right to make changes to this document or the products contained therein without prior notice, to improve performance, reliability, or manufacturability. Application Disclaimer Circuit diagrams may contain components not manufactured by ELMOS Semiconductor AG, which are included as means of illustrating typical applications. Consequently, complete information sufficient for construction purposes is not necessarily given. The information in the application examples has been carefully checked and is believed to be entirely reliable. However, no responsibility is assumed for inaccuracies. Furthermore, such information does not convey to the purchaser of the semiconductor devices described any license under the patent rights of ELMOS Semiconductor AG or others. Copyright 29 ELMOS Semiconductor AG Reproduction, in part or whole, without the prior written consent of ELMOS Semiconductor AG, is prohibited. ELMOS Semiconductor AG Application Note QM-No.: 25AN1E /19

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