Application Note, Rev. 1.1, September 2008 Application Note TLE8110EE How to drive a unipolar stepper motor with the TLE8110EE By Max Bacher Automotive Power Application Note TLE8110EE driving a unipolar stepper motor Table of Contents Page 1 Abstract .......................................................................................................................................3 2 2.1 2.2 2.3 2.4 Introduction.................................................................................................................................3 Table of abbreviations ..................................................................................................................3 Comparison between bipolar and unipolar stepper motor.............................................................3 The Blind Time Functionality of the TLE8110EE...........................................................................5 The Reverse Current Protection Functionality of the TLE8110EE ................................................5 3 3.1 3.1.1 3.1.2 3.1.3 3.1.4 3.2 3.2.1 3.2.2 3.2.3 3.2.4 TLE8110EE behavior driving unipolar EGR stepper motor .....................................................7 Normal operating mode ................................................................................................................7 Circuit ...........................................................................................................................................7 Diagnosis......................................................................................................................................7 Analysis ........................................................................................................................................8 Conclusion..................................................................................................................................10 Stopping the stepper motor.........................................................................................................11 Circuit .........................................................................................................................................11 Diagnosis....................................................................................................................................11 Analysis ......................................................................................................................................12 Conclusion..................................................................................................................................14 4 4.1 4.2 4.3 4.4 Driving EGR stepper motor at battery voltages below 8V .....................................................15 Circuit .........................................................................................................................................15 Diagnosis....................................................................................................................................15 Analysis ......................................................................................................................................16 Conclusion..................................................................................................................................23 5 Conclusion ................................................................................................................................24 6 6.1 6.2 Additional Information .............................................................................................................24 Short product characteristics for the used stepper motor............................................................24 Table of Figures..........................................................................................................................25 Application Note 2 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor 1 Abstract This Application Note is intended to show the TLE8110EE behavior in interaction with a unipolar EGR stepper motor. The different operating modes of the stepper motor are described. The TLE8110EE must control the motor in each of these modes without setting unwanted diagnosis entries. The TLE8110EE has a unique diagnostic feature called Diagnosis Blind Time which enables the device to fulfill this requirement. To be familiar with the two main types of stepper motor the different between the two types are also illustrated. The TLE8110EE is a member of the Flex family and is a smart 10 channel low-side switch for engine management loads (injectors, coils, relays, stepper motors…). Please have also a look to the data sheet from the TLE8110EE to have a deeper understanding of the device. 2 Introduction Please be aware: • All measures in this application note are done with accuracy but we don’t guarantee the results. This application note can be changed without information. • Please refer to the official TLE8110EE data sheet for detailed technical description. 2.1 Table of abbreviations EGR Exhaust Gas Recirculation. RCP Reverse Current Protection. Special device setting for the TLE8110EE. DBTx Diagnosis Blind Time. Special device setting for the TLE8110EE. Two settings for 2.5ms (typical) or 5ms (typical). HVAC Heating, Ventilating and Air-Conditioning. 2.2 Comparison between bipolar and unipolar stepper motor The stepper motor is an electrically commutated motor. The basic operation principle is that of a synchronous machine, i.e. a magnetic rotor is moving synchronous to the rotating magnetic field. The key feature of a stepper motor is that it is driven pulse-wise, which leads to the following advantages and disadvantages: Advantages of a stepper motor • Precise positioning without feedback loop due to step-wise operation. • High torque at low speed or single steps. • High holding torque. • High reliability and life-time, no brushes. Disadvantages of a stepper motor • Driver electronics have to be adapted to specific motor type. • Step loss is possible at excessive torque. • Can oscillate. In automotive applications, stepper motors are mostly used for low- to medium power positioning applications like HVAC flaps, head light beam leveling, idle-speed bypass or EGR valves. Application Note 3 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor To specify a stepper motor, the following properties have to be taken into account. • Number of phases: Two phase motors are the most popular; however three or more phase motors are sometimes used. • Unipolar or bipolar drive - see Figure 1: Bipolar drive requires two H-bridges for driving, but uses the full amount of copper windings, so the motor delivers more torque. Unipolar drive only uses half of the winding, but only requires four low-side switches. • Current control or voltage control: Medium- and high-performance stepper motors have low-ohmic coils, so the coil current has to be controlled by the stepper-motor driver by means of chopper current control. Low-power stepper motors have coils with such high resistance that they are simply switched on, so no current control is necessary over a specified supply voltage range. • The TLE 8110EE is designed to support unipolar, constant voltage stepper motor applications. For more information on other stepper motor driver products, please visit www.infineon.com/motordrivers. Bipolar stepper motor Unipolar stepper motor Stepper_Motors.vsd Figure 1: Stepper motors Application Note 4 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor 2.3 The Blind Time Functionality of the TLE8110EE In specific application cases, such as driving a unipolar stepper motor, it is possible that reverse currents will flow through a channel. Reverse current occurs when there is a current out of the output instead into the output. This behavior could be when you have an application with inductive loads. This reverse current can disturb the diagnosis circuit in a neighboring channel, causing wrong diagnosis results. To reduce the possibility that this occurs, the fault filter times of channels 7 to 10 can be extended to 2.5ms (typical) or 5ms (typical) by setting the “Diagnosis Blind Time” - bits (DEV.DBTx). In Figure 2 we see the behavior for the DBT. For more details about this functionality please refer to the data sheet. Diagnosis Blind Time [DBT] activation DBT is triggered by Open Load [OL] or Short-to-Ground [SG] -detection during OFF-condition of CH7-10. DBT is activated by DEVS.DBT1, DEVS.DBT2 (see „Control of the device“). INx Signal Channel 7 - 10 OFF OL, SG -Diagnosis active ON Output Voltage (-> Diagn. Error) Threshold to detect an error (Open load or short to ground) Diagnosis Blind Time [DBT] triggered by Diagnostic Incident Diagnosis Blind Time [DBT] active DBT „Blind“ window finishes as soon as the error disappears within the DBT 1 1 terr< tDBT 1 1 terr< tDBT terr > tDBT 1 1 Diagnostic Register Entry, because Failure present after ending DBT Diagnosis Register: 11: No Error 10: Over Load 01: Open Load 00: Short to Ground 0 0 DBT.vsd Figure 2: Blind time functionality 2.4 The Reverse Current Protection Functionality of the TLE8110EE For failure cases that result in reverse currents, the device contains a "Reverse Current Protection Comparator" [RCP]. The RCP feature can be activated by setting the DEVS.RCP bit via the SPI interface. When the RCP feature is activated, a comparator monitors the output voltage. When the output voltage is below -0.3V, the output transistor is turned on to prevent unwanted substrate current flow. If the reverse current exceeds a certain value, the transistor is turned off, and the current will flow through the body diode of the output transistor. The RCP function will latch the transistor in the off state until the reverse current decays to zero again. Only then can the comparator be activated again after a delay time tRCP_on_delay. This function reduces the un-wanted influence of a reverse current to the analogue part of the circuit (such as the diagnosis). Application Note 5 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor In Figure 3 we see the behavior for the RCP. In Figure 4 we see the typical reverse current threshold over temperature for the three channel groups. For more details about this functionality please refer to the data sheet. Figure 3: RCP functionality Typical Reverse RevC Current vs. Threshold Channel vs. Temp. Groups Channel Groups Reverse Current forTemp. RCP vs. Temp. Channel Groups -0,1 -40 -20 0 20 40 60 80 100 120 140 ReverseCurrent Current[A] [A] Reverse -0,3 -0,3 -0,5 -0,5 -0,7 -0,7 -0,9 -0,9 -1,1 -1,1 Ch. 1-4 Ch. Ch. 1-4 5-6 Ch. Ch. 5-6 7-10 -1,3 -1,3 -1,5 -1,5-40 -20 0 20 40 60 80 100 120 140 Ch. 7-10 Temperature [°C] Figure 4: Typically values for the RCP current Application Note 6 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor 3 TLE8110EE behavior driving unipolar EGR stepper motor 3.1 Normal operating mode Several tests with different voltages and temperatures had been done with a unipolar stepper motor. The TLE8110EE controls the EGR stepper motor and no diagnosis errors are stored in the corresponding registers of the TLE8110EE. At least one coil from a coil couple (e.g. one couple is connected to Out7 and Out8) is turned on. Stopping the stepper motor is not a normal operating mode (no currents through all coils). This operating mode is descriped in chapter 3.2. 3.1.1 Circuit Figure 5 shows how the TLE8110EE is connected with the stepper motor. The red marked signals in Figure 5 are plotted in Figure 7 to Figure 9 (In7, Out7, Iout 7 and VDD). Vcc Vdd Vbat SPI_CS SPI_CLK Stepper motor TLE8110E Iout 7 SPI_SI L SPI_SO R µC R In7 L In8 Phase-A Out7 In9 Phase-B Out8 In10 GND L Phase-C Out9 R R L Phase-D Out10 GND GND Max Bacher Flex10_Stepper_Motor_P1.emf Figure 5: TLE8110EE with stepper motor 3.1.2 Diagnosis When the stepper is driven in normal operating mode there is no unwanted diagnosis entry. This means we need no special device settings just like DBT or RCB for this operating mode to avoid unwanted diagnosis entries. Normal operating mode is the mode when the coils are supplied with current shown in Figure 5 and Vbat is not below 8Volts. Application Note 7 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor 3.1.3 Analysis The stepper motor is driven with the pattern shown in Figure 6. This pattern is repeated continuously. There is always a current flow through one coil at least. Figure 6: Control sequence The Figure 7 to Figure 10 shows the unproblematic interaction of the TLE8110EE with the unipolar stepper motor. The test conditions are various voltages from VDD, VCC, VBat and various temperatures. We can see that there is no need for additional device settings to avoid unwanted diagnosis entries. TLE8110EE Tambient: -40°C EGR Tambient: -40°C VDD: 5.5V VCC: 5.5V Vbat: 24V Normal_Operation_-40C_24V.emf Figure 7: Normal operating mode at worst case boundary conditions (T=-40°C, Vbat=24V) Application Note 8 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor TLE8110EE Tambient: 25°C EGR Tambient: 25°C VDD: 4.5V VCC: 3V Vbat: 13.5V Normal_Operation_25C.emf Figure 8: Normal operating mode at low VCC and VDD (T=25°C, Vbat=13.5V) TLE8110EE Tambient: -40°C EGR Tambient: -40°C VDD: 4.5V VCC: 3V Vbat: 13.5V Normal_Operation_-40C.emf Figure 9: Normal operating mode at low VCC and VDD (T=-40°C, Vbat=13.5V) Application Note 9 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor TLE8110EE Tambient: 150°C EGR Tambient: 150°C VDD: 4.5V VCC: 3V Vbat: 13.5V Normal_Operation_150C.emf Figure 10: Normal operating mode at low VCC and VDD (T=150°C, Vbat=13.5V) 3.1.4 Conclusion The executed tests show no diagnosis failure with the EGR stepper motor. There is no need for additional device settings. Application Note 10 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor 3.2 Stopping the stepper motor As soon as the control sequence stops the TLE8110EE no current flows through the coils. After switching off all channels, low or negative voltage at the ouput is caused by demagnetization and magnetic coupling. 3.2.1 Circuit Figure 11 shows the connections between µController, TLE8110EE and the stepper motor. The red marked signals in Figure 11 are plotted in Figure 12 and in Figure 13 (OUT 7, OUT8, Iout 7 and Iout 8). Vbat 5V VDD Stepper motor 5V Iout 7 VCC L SPI_CS SPI_CLK SPI_SI µC A TLE8110E R OUT 7 OUT 8 SPI_SO R B L Iout 8 In 7 L R R L In 8 GND GND GND Flex10_Stepper_Motor_P2_mb.emf Figure 11: TLE8110EE with stepper motor and µC 3.2.2 Diagnosis When the motor is stopped (stopping the current flow through all coils) a diagnosis entry: 00 (Short to Ground in OFF-Mode) will be stored in the diagnosis register of the TLE8110EE. The unwanted diagnosis entry can be avoided by setting the diagnosis blind time to 2.5 ms. Application Note 11 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor 3.2.3 Analysis To analyse the unwanted behavior one coil of the motor is set to active for 10ms. We choose this time to be sure that the coil is driven to saturation. The same time is used for normal operation. If the TLE8110EE diagnosis blind time is set to default mode and the motor is stopped then there is a diagnosis entry set for “Short to Ground in OFF-Mode”. The default value for “Diagnosis-Blind-Time” is typically 150µs. Please note if the diagnosis blind time is set to 2.5ms then no unwanted error will be stored into the diagnosis register. Now have a look to Figure 12. Out from Figure 11 we see that the coil connected to “Out7” is called coil “A”. The coil connected to “Out8” is called coil “B”. In this figure we can see that the output voltage for channel 8 is below the open load threshold for about 0.8ms. In this case a diagnosis blind time of 2.5ms is enough to avoid an unwanted diagnosis entry. So we see that we have to use the diagnosis blind time functionality to avoid unwanted diagnosis entries. In this case the setting for the blind time with typical 2.5ms should be enough, but we will see in the next chapters that some applications needs a longer blind time for debouncing. Time (0.8ms) for Vout8 < Short to Ground Threshold Short to Ground Threshold 1.5 Volt Vout8 Stopping_Overview_mb.emf Figure 12: Stopping current flow through the stepper coils Application Note 12 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor In Figure 13 we can see that that the peak of the reverse current is in the range of 600mA. So we can not use the RCP functionality because it’s out of range as described in chapter 2.4. In Figure 14 we see the typical current for the outputs 7 to 10 for RCP functionality. Vout7 Peak of the reverse current (-600mA) Short to Ground Threshold 1.5 Volt Vout8 Stopping_Detail_mb.emf Figure 13: Detail of the foregoing Figure Reverse Current for RCP vs. Temp. Ch. 7-10 -0,1-40 -20 0 20 40 60 80 100 120 140 Reverse Current [A] -0,3 -0,5 -0,7 -0,9 -1,1 Ch. 7 Ch. 8 -1,3 Ch. 9 Ch. 10 -1,5 Temperature [°C] RCP_ChannelGroup-3.vsd Figure 14: RCP current for channels 7 to 10 Application Note 13 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor Coil “A” and coil “B” are magnetic linked. In principle both pairs of coils present a transformer with the translation 1:1. The strongly decreasing magnetic field induces a voltage into coil “B” when current flow through coil “A” is stopped. Because of this induced voltage a reverse current flows through coil “B” about 0.8ms and the output voltage for channel 8 gets below the threshold for short to ground detection. Because of this there is the diagnosis entry “Short to Ground in OFF-Mode” for channel 8. There is no diagnosis entry when the diagnosis blind time from the TLE8110EE is set to 2.5ms: “The diagnosis-logic is now ignoring potential register entries for typically 2.5 ms.” As long as the reverse current during remains < typically 2.5ms, no unwanted entry in the diagnosis register appears. During the normal operating mode there are no diagnosis entries because when an output changes the state from “ON” to “OFF” then the neighbor output changes the state from “OFF” to “ON” and the “Short to Ground” diagnosis is an “OFF-State” diagnosis. Figure 6 shows the control sequence for the stepper motor. 3.2.4 Conclusion The performed tests show no unwanted diagnosis failure with the unipolar EGR stepper motor when the diagnosis blind time is set to 2.5ms. The diagnosis is now debounced for typically 2.5ms. As long as the reverse current duration remains < typ. 2.5ms, no unwanted entry in the diagnosis register appears. Application Note 14 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor 4 Driving EGR stepper motor at battery voltages below 8V The stepper motor is driven with 6 Volt power supply on the outputs. A µController is controlling the TLE8110EE. The control sequence is shown in Figure 6. As an additional challenge we disconnect after some steps the Phase-C of the stepper motor from the output of the TLE8110EE (output 9). Please have a look to the Figure 15. 4.1 Circuit Figure 15 shows the circuit with the µController, the TLE8110EE and the EGR-Valve with the disconnected (opened) Phase-C. Vcc Vdd Vbat with 6 Volt SPI_CS SPI_CLK Stepper motor TLE8110E Iout 7 SPI_SI L SPI_SO R µC R In7 L In8 Phase-A Out7 In9 Out9 In10 GND Phase-B Out8 Opened ! L Phase-C R R L Phase-D Out10 GND GND Max Bacher Flex10_Stepper_Motor_6Volt Figure 15: Circuit with the µController, the TLE8100EE and the EGR-valve with the disconnected (opened) phase-C 4.2 Diagnosis The diagnosis system recognizes the open output and reacts with an “open load” entry for the output 9 of the TLE8110EE which is disconnected from the Phase-C of the stepper motor. After some steps the diagnostic system executes also an “open load” entry for the output 10 of the TLE8110EE which is still connected to Phase-D of the stepper motor. This additional diagnosis entry is unwanted. This behavior of the stepper motor is only seen when Vbat is below 8Volt. This behavior is a weakness of the stepper motor which loses steps when Vbat is below 8 Volts and a phase is disconnected. Application Note 15 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor 4.3 Analysis The Figure 16 shows the channels 9 and 10 of the TLE8110EE when the stepper motor is driven with 6 Volt power supply and all channels are connected. The red line in Figure 16 shows the threshold voltage of the open load detection for the channel 10. This threshold voltage should be in the range from 2.00 Volt to 3.20 voltages. As typical value we measured about 2.68 Volt. Open Load Threshold 2.68 Volt Max Bacher 6V_Normal.emf Figure 16: Stepper motor with 6Volt power supply Application Note 16 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor Figure 17 is from the characterization for the open load threshold of channel 10 for different temperatures and different voltages for VDDs and VCCs. Here we can see that this value is well centered in the allowed range and we can also see that this threshold is stable over temperature and variation of VCC and VCC. Out from the characterization we see a threshold about 2.68 Volt. Hint: The minimum and maximum thresholds (LSL and USL) in the Figure 17 are not the limits from the data sheet. Please have a look to the data sheet to get the thresholds. USER Thomas Salbrechter S1085/TLE8110EE: Temperature/VDD/VCC-Characterization DEPARTMENT Design step: B12 Devices: 40 systems on w afer RU802513V04 #6 (WAFER TEST!) Temperature: -40°C, 25°C, 85°C, 125°C, 150°C AIM AP D PD VI PTE TE INFINEON Page 131 BoxPlot 659;OUT10VOL;value grouped by Legend lo 2 hi 3.2 qty 2400/2400 mean 2.668 sigma 0.0227 cp 8.81 cpk 7.8 USL 3.4 3.2 3 T 659;OUT10VOL;value [V] LEGEND Legend VDD_4.5V / VCC_3V 2.8 VDD_4.5V / VCC_4V VDD_4.5V / VCC_5.5V VDD_4.5V / VCC_5V 2.6 VDD_5.5V / VCC_3V VDD_5.5V / VCC_4V VDD_5.5V / VCC_5.5V 2.4 VDD_5.5V / VCC_5V VDD_5V / VCC_3V VDD_5V / VCC_4V 2.2 VDD_5V / VCC_5.5V LSL VDD_5V / VCC_5V 2 1.8 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 temp 70 80 90 100 110 120 130 140 150 160 Figure 17: Characterization for open load threshold Application Note 17 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor In Figure 18 we see that the voltage on output 10 is below the open load threshold. The open load threshold is marked with a red line and is about 2.68 Volt. This behavior is seen when we drive the stepper motor with Vbat below 8 Volt and disconnecting the phase-C of the stepper motor from the output 9 of the TLE8110EE. In this case we have 6Volt for Vbat. Hint for the output voltage on the channel 9: On the output of channel 9 is always a LED connected. This is a special behavior of the lab board to see the state of the output. Because of this we see on the output of channel 9 always a voltage when the channel is switched off- even when the wire of the stepper motor is disconnected. Open Load Threshold 2.68 Volt Open Load Detection Max Bacher 6V_OL_ThrsH_CH10.emf Figure 18: Stepper motor with 6Volt power supply and disconnected phase-D Application Note 18 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor In Figure 19 we see red market the open load detection for output 10. Output 10 is connected with the phase-D of the stepper motor. When there are no special device settings for a longer blind time we have an unwanted open load diagnosis entry for channel 10. In the Figure 20 we discuss the behavior in detail. The blue line in the Figures is an external trigger signal to catch the right moment. Figure 19: Overview of the open load detection for channel 10 The Figure 20 shows the behavior from Figure 19 with a higher time resolution - 1ms against 10ms in the figure before. The green line is the voltage on channel 10. We see that the voltage is for a longer time than the DBT1 (Diagnosis Blind Time 1) below the open load threshold. Open Load Threshold 2.68 Volt > BT BT Max Bacher 6V_OL_CH10_BT25-F_Detail.emf Figure 20: Detail of the open load detection for channel 10 Application Note 19 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor DBT1 has a typical value of 2.5 ms and is in the range of 1.75 ms to 3.25 ms. Without setting the diagnosis blind time to a higher value we have an unwanted open load diagnosis entry for this special case. But we can also see that this diagnosis entry is no failure of the TLE8110EE. It’s the behavior of the stepper motor which is not able to drive without losing steppes when Vbat is 6 Volt and disconnecting one phase. The value of the voltage measured on the output is the superposition of: • Voltage caused by the resistive load. • Voltage induced by the inductive load. • Voltage caused by the transformer principle. In principle both pairs of coils present a transformer with the ratio 1:1. • Voltage induced by the rotating rotor with its magnetic field. The voltage induced by the rotating magnetic field could be measured in an indirect way: • The measured voltage on the output is the superposition of all voltages. • There is no rotating magnetic field when the stepper motor is disassembled (the rotor is removed from the stepper motor, so it could not rotate and generate the rotating magnetic field). • In this case there is no contribution to the superposition of the voltages. • Now the effect from the rotating magnetic field could be seen in an indirect way. Application Note 20 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor Figure 21 shows the output voltage form the channels 7 to 10 with the assembled and also with the disassembled stepper motor. On this channels are the coils from the stepper motor connected. Vbat for the stepper motor is 6 Volt. Assembled stepper motor Vout10 Vout10 Vout9 Vout9 Vout8 Vout8 Vout7 Vout7 Max Bacher 6V_Compare_Assemble.emf Disassembled stepper motor Max Bacher 6V_Compare_Disassemble.emf Figure 21: Output voltage for the assembled and disassembled stepper motor Figure 22 shows the output voltage form the channels 7 to 10 with the assembled and also with the disassembled stepper motor. Channel 9 is not connected to the phase-C of the stepper motor. All other channels are connected to the stepper motor. Vbat for the stepper motor is 6 Volt. Assembled stepper motor Vout10 Vout10 Vout9 Vout9 Vout8 Vout8 Vout7 Vout7 Max Bacher 6V_Compare_OPEN-Ch9_Assemble.emf Disassembled stepper motor Max Bacher 6V_Compare_OPEN-Ch9_Disassemble.emf Figure 22: Output voltage for the assembled and disassembled stepper motor with disconnected phase-C There are three effects because of the rotating magnetic field: • The amount of the induced voltage depends on the rotating speed (the absolute value). • There are two possibilities for the algebraic sign of the induced voltage: It could depend on the rotor rotation direction or it’s also possible that the magnetic field form the rotor is on the wrong position (one phase displaced). • The time stamp where the induced voltage appears depends on the position of the rotor (phase shifting) Application Note 21 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor The Figure 23 shows the influence of the speed from the magnetic field. The rotating of the magnetic field from the rotor induced a voltage into the coils. When the rotating speed of the magnetic field increases, the absolute value of the voltages also increases. When the rotating speed of magnetic field decreases, the absolute value of the voltage also decreases. Vout10 Vout9 Vout8 Vout7 Max Bacher 6V_Compare_OPEN-Ch9_P1.emf Figure 23: Influence of the speed from the magnetic field to the output voltages Figure 24 shows the influence of the induced voltage from the magnetic field. There are two possibilities for the algebraic sign: It could depend on the rotor rotation direction or it’s also possible that the magnetic field from the rotor is on the wrong position (one phase displaced). + Vout10 - Vout9 Vout8 Vout7 Max Bacher 6V_Compare_OPEN-Ch9_P2.emf Figure 24: Influence of the acceleration from the magnetic field to the output voltages Application Note 22 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor Figure 25 shows the influence of the time stamp from the induced voltage. The time where the induced voltage appears depends on the position of the rotor (phase shifting). The position of the rotor is a little different between the steps. This means that the position of the rotor is not always on the same position when the output is turned on. Vout10 Vout9 Vout8 Vout7 Max Bacher 6V_Compare_OPEN-Ch9_P3.emf Figure 25: Influence of the induced voltage regarding the time 4.4 Conclusion The operation mode of the stepper motor is with Vbat 6 Volt near the limit (maybe losing steps). In 6 Volt operations mode the stepper motor loses steps when disconnecting an output. The stepper motor doesn’t work proper now. This losing of steps occurs in a change of the speed and the phase from the rotor. With the rotor also the magnetic field (from the rotors permanent magnets) is changed very fast. So it’s possible that the magnetic field is some times on the wrong position. And so the voltage on the neighbor channel could be below the threshold of the OFF-mode diagnosis detection. Hint: The descript loosing of steps behavior is from the mathematical point of view a not linear and also a random behavior. So we could not calculate in easy mathematical terms when the descript behavior for the neighbor channels appear. Application Note 23 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor 5 Conclusion The Flex TLE8110EE is able to drive a unipolar stepper motor in a large number of operations modes. With the special feature of the diagnosis blind time it’s also possible to drive the stepper motor with a Vbat below 8 Volt and with a disconnected phase. With special feature the Flex TLE8110EE provides no unwanted diagnosis entries to the µController. So we can say: The Flex TLE8110EE is able to recognize the weakness of external devices and protects in this way the µController. We recommend enabling the DBT and RCP functions for unipolar stepper motor applications. In normal operation (without an open connection or short circuit), the TLE8110EE diagnostics function properly when Vbatt is greater than 6V. An open circuit between the TLE8110EE and the stepper motor may cause a wrong diagnostic result when Vbatt is less than 8V (two open faults set instead of one). 6 Additional Information 6.1 Short product characteristics for the used stepper motor Figure 26 shows the electrical connections for the unipolar stepper motor and Table 1 shows the short product characteristics. Please note: “The stepper motor was not disassembled for these measurements”. 2 1 4 5 1: Phase A 2: VB 3: Phase B 4: Phase C 5: VB 6: Phase D 3 6 Phase A VB Phase B Phase C VB Phase D Figure 26: Electrical connections of the stepper motor Table 1: Characteristics for stepper motor Phase A-B Phase A-VB Phase B-VB Phase C-D Phase C-VB Phase D-VB L = 56.5 mH L = 14 mH L = 13.9 mH L = 55.9 mH L = 13.8 mH L = 13.8 mH R = 45 Ω R = 22.5 Ω R = 22.5 Ω R = 44.9 Ω R = 22.4 Ω R = 22.5 Ω Application Note 24 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor 6.2 Table of Figures Figure 1: Stepper motors..........................................................................................4 Figure 2: Blind time functionality...............................................................................5 Figure 3: RCP functionality.......................................................................................6 Figure 4: Typically values for the RCP current .........................................................6 Figure 5: TLE8110EE with stepper motor.................................................................7 Figure 6: Control sequence ......................................................................................8 Figure 7: Normal operating mode at worst case boundary conditions (T=-40°C, Vbat=24V) ................................................................................................................8 Figure 8: Normal operating mode at low VCC and VDD (T=25°C, Vbat=13.5V).......9 Figure 9: Normal operating mode at low VCC and VDD (T=-40°C, Vbat=13.5V) .....9 Figure 10: Normal operating mode at low VCC and VDD (T=150°C, Vbat=13.5V).10 Figure 11: TLE8110EE with stepper motor and µC ................................................11 Figure 12: Stopping current flow through the stepper coils.....................................12 Figure 13: Detail of the foregoing Figure ................................................................13 Figure 14: RCP current for channels 7 to 10 ..........................................................13 Figure 15: Circuit with the µController, the TLE8100EE and the EGR-valve with the disconnected (opened) phase-C ............................................................................15 Figure 16: Stepper motor with 6Volt power supply .................................................16 Figure 17: Characterization for open load threshold ...............................................17 Figure 18: Stepper motor with 6Volt power supply and disconnected phase-D ......18 Figure 19: Overview of the open load detection for channel 10..............................19 Figure 20: Detail of the open load detection for channel 10....................................19 Figure 21: Output voltage for the assembled and disassembled stepper motor ....21 Figure 22: Output voltage for the assembled and disassembled stepper motor with disconnected phase-C............................................................................................21 Figure 23: Influence of the speed from the magnetic field to the output voltages ...22 Figure 24: Influence of the acceleration from the magnetic field to the output voltages..................................................................................................................22 Figure 25: Influence of the induced voltage regarding the time ..............................23 Figure 26: Electrical connections of the stepper motor ...........................................24 • For further information you may contact http://www.infineon.com/ Application Note 25 2008-September-08 Application Note TLE8110EE driving a unipolar stepper motor AP Number Revision History: 2008-09-01; Rev. 1.1 Previous Version: Rev. 1.0 Page 24 Subjects (major changes since last revision) Add text in chapter 5: We recommend enabling the DBT and RCP functions for unipolar stepper motor applications. In normal operation (without an open connection or short circuit), the TLE8110EE diagnostics function properly when Vbatt is greater than 6V. An open circuit between the TLE8110EE and the stepper motor may cause a wrong diagnostic result when Vbatt is less than 8V (two open faults set instead of one). AP Number Revision History: 2008-04-24; Rev. 1.0 Previous Version: none Page Application Note Subjects (major changes since last revision) 26 2008-September-08 Edition 2006-02-01 Published by Infineon Technologies AG 81726 Munich, Germany © Infineon Technologies AG 2008. All Rights Reserved. LEGAL DISCLAIMER THE INFORMATION GIVEN IN THIS APPLICATION NOTE IS GIVEN AS A HINT FOR THE IMPLEMENTATION OF THE INFINEON TECHNOLOGIES COMPONENT ONLY AND SHALL NOT BE REGARDED AS ANY DESCRIPTION OR WARRANTY OF A CERTAIN FUNCTIONALITY, CONDITION OR QUALITY OF THE INFINEON TECHNOLOGIES COMPONENT. THE RECIPIENT OF THIS APPLICATION NOTE MUST VERIFY ANY FUNCTION DESCRIBED HEREIN IN THE REAL APPLICATION. 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