ATA6830-PKH

Features • • • • • • 2-Phase 1 A Stepping Motor Driver Compensated Half Step Operation Chopper Current Control Unidirectional Single Wire Bus Interface with Error Feedback Intelligent Travel Operation Control Referencing by Extending or Retracting Application • Dynamic Headlamp Adjustment Benefits • • • • Error Recognition with Feedback Short Circuit Protected Outputs Overtemperature Warning and Shut Off Supply Voltage Supervision Intelligent Stepper Motor Driver ATA6830 Electrostatic sensitive device. Observe precautions for handling. Description The circuit serves to control a stepping motor for dynamic headlamp beam adjustment in automobiles. Two chopper-controlled H-bridges serve as the stepping motor driver. The circuit receives the commands to control the stepping motor by means of a unidirectional serial single-wire bus. An integrated process control independently moves the stepping motor into the new desired position. This allows it to be automatically accelerated and slowed down. The stepping motor is operated in compensated half-step operation. The maximum clock frequency at which the stepping motor is operated depends on the supply voltage, the chip temperature, the operating mode, and position difference. Rev. 4575C–BCD–05/03 1 Voltage Regulator VSS Supply Monitor COS Oscillator VDD Temperature Monitor RSET Biasing AGND Figure 1. Block Diagram BUS UART VBAT1A VBAT1B Command Interpreter SM1B SRA Driver Logic Driver Logic Cruising Service Control SM1A SRB SM2A SM2B VBAT2A VBAT2B Test Logic ATA6830 Pin Configuration n.c. COS RSET AGND VSS VDD BUS Figure 2. Pinning QFN 28 28 27 26 25 24 23 22 VBAT1A 1 21 VBAT1B n.c. 2 20 n.c. SM1A 3 19 SM1B SRA 4 18 SRB SM2A 5 17 SM2B n.c. 6 16 n.c. VBAT2A 7 15 VBAT2B MLP 7x7mm 2 9 10 11 12 13 14 SCI1 SCI2 SCO2 TA TTEMP n.c. 8 SCO1 0.8mm pitch ATA6830 28 lead ATA6830 4575C–BCD–05/03 ATA6830 Pin Description Pin Symbol Function 1 VBAT1A Battery voltage 2 n.c. Not connected 3 SM1A 4 SRA 5 SM2A 6 n.c. 7 VBAT2A Battery voltage 8 n.c. Not connected 9 SCI1 Test pin, please connect to ground for EMC reasons 10 SCO1 Test pin, please connect to ground for EMC reasons Connection for stepping motor winding A Sense resistor A connection Connection for stepping motor winding A Not connected 11 SCI2 Test pin, please connect to ground for EMC reasons 12 SCO2 Test pin, please connect to ground for EMC reasons 13 TA Test pin, please connect to ground for EMC reasons 14 TTEMP Test pin, please connect to ground for EMC reasons 15 VBAT2B Battery voltage 16 n.c. Not connected 17 SM2B 18 SRB 19 SM1B 20 n.c. Not connected 21 VBAT1B Battery voltage 22 BUS Receives the control instructions via the single wire bus from the controller 23 VDD 5 V supply voltage output 24 VSS Digital signal ground 25 AGND Analog signal ground 26 RSET Reference current setting. Connected externally with a resistor to AGND. The value of the resistor determines all internal current sources and sinks. 27 COS Oscillator pin, connected externally with a capacitor to AGND. The value of the capacitance determines the chopper frequency and the baud rate for data reception. 28 n.c. Not connected Connection for stepping motor winding B Sense resistor B connection Connection for stepping motor winding B 3 4575C–BCD–05/03 Functional Description Analog Part Figure 3. Analog Blocks VBAT VDD Supply Bias Oscillator Bias Generator Bandgap Voltage Regulator Voltage Supervisor Temperature Supervisor Voltage Levels Temperature Levels Clock Reset COS RSET AGND VSS The circuit contains an integrated 5 V regulator to supply the internal logic and analog circuit blocks. The regulator uses an adjusted bandgap as voltage reference. Also all other parts that require an excellent voltage reference, such as the voltage monitoring block refer to the bandgap. The bias generator derives its accurate currents from an external reference resistor. The oscillator is used for clocking the digital system. All timings like the baud rate, the step duration and the chopper frequency are determined from it. An external capacitor is used for generating the frequency. The voltage monitoring enables the circuit to drive the stepping motor at different battery voltage levels. According to the battery voltage the stepping motor will be accelerated to a maximum step velocity. In case of under or over voltage the motor will shut off. A temperature monitoring is used for shut off at overtemperature conditions and current boost in case of low temperature. 4 ATA6830 4575C–BCD–05/03 ATA6830 Digital Part Figure 4. Digital Blocks Clk Step Time Memory Reset Voltage Levels Maximum Step Time Temperature Signals New Step Time Actual Step Time Error Signals UART BUS VREF shiftclk Clock Recovery bitstream Bitstream Recovery rxd reference run Data Recognition & Parity-Check new position Cruise Control Stepper Motor Control Desired Position Instantaneous Position Error Timer Error Signals Figure 4 shows all digital blocks of the circuit. The stepping motor will be controlled by commands via the bus input pin. An analog comparator is used as a level shifter at the input. There is also a possibility of clamping the bus pin to ground. This will be used after detecting an error to feedback this to the microcontroller. The next block is a UART. Its task is clock recovery and data recognition of the incoming bit stream. For clock recovery a special bitstream is used after each power on. The generated bitstream will be analyzed and after a correct parity check interpreted for execution. A sophisticated cruise control generates all control signals for the two H-bridge drivers. It uses an internal step-time table for accelerating and decelerating the stepping motor depending on the actual and desired position and the temperature and voltage levels. Exception handling is integrated to interpret and react on the temperature, supply voltage, and coil-current signals from the analog part. 5 4575C–BCD–05/03 Stepping Motor Driver Figure 5. H-bridge Driver Stage Stepper Motor Control Driver Logic Error Signals VBAT SM1x SM2x Temperature Shutdown Temp. Shutdown Temperature Warning Temp. Warning Clk SRx Vref Reset Shunt Figure 5 shows the diagram of one H-bridge driver stage. It consists of two NMOS and two PMOS power transistors. An external shunt is used for measuring the current flowing through the motor coil. Additional comparators and current sensing circuitry is integrated for error detection. Data Communication The circuit receives all commands for the stepping motor via a single wire bus. In idle mode the bus pin is pulled up by an internal current source near to VBAT voltage. During the transmission the external transmitter has to pull down the bus level to send information about data and clock timing. The used baud rate has to be about 2400 baud. Because of oscillator tolerances a synchronization sequence has to be sent at the beginning of data transfer. Figure 6 shows the pattern used for this sequence. The circuit uses the 1-0-1-0 sequences for adjusting the internal bit time. Later on during data transfer every 1-0-1-0 sequence coming up randomly is used for resynchronization. Thus all tolerances that occur during operation will be eliminated. To obtain a synchronization of up to 15% oscillator tolerance the pattern has to be sent at least 4 times. 6 ATA6830 4575C–BCD–05/03 ATA6830 Figure 6. Synchronization Sequence SYNCHRONIZATION PATTERN PARITY BIT START BIT START BIT PARITY BIT STOP BIT STOP BIT Between two commands a pause has to be included. This is necessary for a clear recogition of a new message frame (command). Figure 7 shows the timing diagram of two commands. Figure 7. Message Frame and Space MESSAGE FRAME HIGH BYTE SPACE LOW BYTE Every command consists of 16 bits. They will be sent with two bytes. Figure 8 shows the message frame. The high byte is sent first, immediately followed by the low byte. Every byte starts with a start bit and ends with a parity bit and a stop bit. The first start bit (level 0) after a pause (level 1) indicates the beginning of a new message frame. The value of the parity bit has to be odd, i.e., the crossfooting of the byte including the parity bit is odd. If a data packet is not recognized due to a transmission error (parity error), the entire command is rejected. Figure 8. Command Bits MESSAGE FRAME HIGH BYTE LOW BYTE PARITY BIT 7 START BIT 6 5 4 3 8 DATA BITS 2 1 0 7 STOP BIT PARITY BIT START BIT 6 5 4 3 8 DATA BITS 2 1 0 STOP BIT 7 4575C–BCD–05/03 Bus Commands There are different commands for controlling the stepping motor. Table 1 shows a list of all implemented commands and their meanings. The first command, the synchronization sequence, is described above. The second group of commands are the reference commands. A reference run command causes the stepping motor to make an initial run. It is used to establish a defined start position for the following position commands. The way the reference run is executed will be described later. There are two reference run commands. The difference is the turn direction of the stepping motor. This makes the circuit more flexible for different applications. The turn direction is coded in the 4 identifier bits. Table 1. Bus Commands High Byte Data Mode Low Byte Identifier Data Bus Command 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 Synchronization 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 Reference run (extend) 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 0 Reference run (retract) 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 New position (0 = full extension) D8 D9 0 0 1 0 0 1 D0 D1 D2 D3 D4 D5 D6 D7 New position (0 = full retraction) D8 D9 0 0 0 1 1 0 D0 D1 D2 D3 D4 D5 D6 D7 New position (testmode, 0 = full extension) D8 D9 1 1 1 0 0 1 D0 D1 D2 D3 D4 D5 D6 D7 New position (testmode, 0 = full retraction) D8 D9 1 1 0 1 1 0 D0 D1 D2 D3 D4 D5 D6 D7 The last class of commands are the position commands. Every new position will be sent as an absolute value. This makes the transmission more safe in terms of losing a position command. The next received command tells the stepping motor the right position again. For the position data there are 10 bits available (D0 to D9). The maximum possible step count to be coded with 10 bit is 1024. Though position commands up to 1024 will be executed, it´s prohibited to use values higher than 698, as this is the step count of the reference run. For details see chapter “Reference Run”. There are 4 new position commands. They differ in the identifier and in the modus bits. The identifier fixes the turn direction. For test purposes there are new position commands with a different mode. In this mode the stepping motor works with a reduced coil current. This may be used for end tests in the production of the application. Any command with modus or identifier different to the first reference run will be ignored. Thus it is also not possible to change modus or identifier by performing a second reference run. 8 ATA6830 4575C–BCD–05/03 ATA6830 Power-up Sequence After power-up the circuit has to be synchronized and a reference run has to be executed before a position command can be carried out. Figure 9 shows a timing diagram on how the necessary sequences follow each other. Figure 9. Necessary Commands after Power-up POWER UP SYNCHRONIZATION SEQUENCE REFERENCE RUN SEQUENCE POSITION 1 POSITION 2 1 2 4 1 2 10 MESSAGE FRAME The first sequence is the synchronization sequence. Its pattern (Figure 6) should be sent at least 4 times to be sure that the following commands will be recognized. If there are distortions on the bus it is helpful to send this sequence more than 4 times. A RC lowpass filter at the bus pin (Figure 16) helps to reduce distortsions. After synchronization the stepping motor has to make the reference run to initialize its zero position. The first reference run will only be executed if the circuit recognizes this command three times in series. This function is implemented contributing to the importance of the reference run. After the reference run the circuit will switch to normal operation. To perform a reference run during normal operation, the command has to be sent only once. Figure 10 shows the state diagram for the implemented sequence processor. 9 4575C–BCD–05/03 Figure 10. Flow Diagram for the Power-up Sequence reset state N synchronization Y idle state N 3 successive reference run commands Y reference run Y cruise control 10 new position? N idle state ATA6830 4575C–BCD–05/03 ATA6830 Reference Run In normal operation, new position commands are transmitted as absolute values. To drive the stepping motor to these absolute positions, the circuit has to know the motor’s zero position. Therefore, the stepping motor has to perform a reference run after each power-up in which it is extended or retracted to its limit stop. Before the execution of the reference run, the motor is supplied with hold current. As the actual position is not known at the beginning of the reference run the whole position range has to be passed. To optimize performance for smaller actuators, the reference run has been reduced to 698 steps. Therefore, it is prohibited to access positions higher than 698, because in a following reference run the stepping motor would not reach its zero position. If it is necessary that the entire range up to position 1024 can be used, the reference run has to be executed twice. Since any command during reference run is ignored, the second reference command has to be sent about 2.4 s after the first command. To avoid any possible mistake, e.g., the loss of a step during the reference run or the bouncing at the limit stop, there is a special run to be executed. This is shown in Table 2. Table 2. Reference Run Course Phase Action Ramp up to 446 Hz step frequency Drive through I Drive at constant speed Ramp down to minimum step frequency (303 Hz) the whole range (698 steps) II III Cruise Control Int. Counter Steptime 704 3300 µs 703 2895 µs 702 2540 µs 701 2240 µs 700 to 11 2240 µs 10 2240 µs 9 2549 µs 8 2895 µs 7 to 6 3300 µs 6 3300 µs 5 to 0 3300 µs IV Wait for 6 ´ 3300 µs with the last coil current V Perform another 6 steps with 3300 µs VI Wait for 5 ´ 3300 µs with the last coil current 0 3300 µs VII Set current to hold current; normal operation varied varied The travel operation control independently moves the stepping motor into its new position. To reach the new position as fast as possible but without abrupt velocity changes, the stepping motor is accelerated or slowed down depending on the difference between actual and nominal position. If this difference is huge the stepping frequency will increase (acceleration). When the new position is nearly reached, the frequency will decrease again (deceleration). In the case of a new nominal position opposite to the direction of the motion being from the microcontroller, the stepping frequency will decrease to its starting value (300 Hz) before the direction can turn. The cruise control is shown in Figure 11. The possible stepping frequencies for velocity control are shown in Table 3. 11 4575C–BCD–05/03 Figure 11. Dynamic Frequency Adaption frequency present frequency minimum frequency (300 Hz) present position nominal position time t+1 nominal positon time t position Table 3. Frequency Ramp Number Step Frequency (Hz) Step Time (µs) 1 303 3300 2 345 2895 3 394 2540 4 446 2240 5 493 2030 6 538 1860 7 575 1740 8 613 1630 9 649 1540 10 680 1470 11 714 1400 12 741 1350 13 769 1300 14 800 1250 15 826 1210 16 855 1170 17 877 1140 18 901 1110 19 926 1080 20 952 1050 21 980 1020 22 1000 1000 In addition to the actual step frequency there is a maximum step frequency up to which the actual step frequency can rise. To secure a correct operation at low supply voltages the maximum value for the stepping frequency is smaller at low voltages. If the supply voltage falls below the 9 V threshold, travel operation will suspend. To restart operation, the supply voltage has to rise above 10.5 V. The relation of the maximum step frequency and the supply voltage during operation is shown in Table 4. 12 ATA6830 4575C–BCD–05/03 ATA6830 If the chip temperature exceeds the overtemperature warning threshold, the step speed is reduced to 300 Hz. If the chip temperature rises further the output driver is shut off. Table 4. Maximum Step Frequency Step Operation VBAT Maximum Step Frequency at Rising Voltage Maximum Step Frequency (VBAT once > 10.5 V) 11 V 1000 Hz (1 ms) 1000 Hz (1 ms) > 20 V No operation No operation The stepping motor is operated in halfstep-compensation mode. The current for both coils is shown in Figure 12. The current levels are increased when the temperature is below 0°C to secure operation. For final tests at the end of the application production line the currents are reduced. Figure 12. Compensated Halfstep Operation coil A 700mA 500mA half steps -500mA -700mA coil B 1 2 3 4 5 6 7 8 700mA 500mA half steps -500mA -700mA Bridge Current Control The bridge current is controlled by a chopper current control, shown in Figure 13. The current is turned on every 40 µs (25 kHz chopper frequency). The current flow in the Hbridge is shown in Figure 14a. After a blanking time of 2.5 µs to suppress turn-on peaks the current is measured via the shunt voltage. As soon as the current has reached its nominal value it is turned off again. The current flow in this state is shown in Figure 14b. 13 4575C–BCD–05/03 Figure 13. Chopper Current Control turn on signal Imax coil current flyback comparator shunt resistor voltage blanking time Figure 14. Current Flow in Halfbridge ON OFF ON ON OFF ON OFF OFF a) Exception Handling b) During operation, different exceptional states or errors can arise to which the circuit must correspondingly react. These are described below: • Supply voltage below 9 V Travel operation is suspended for the duration of the undervoltage. The output current will be set to zero. When the supply voltage rises above 10.5 V, travel operation restarts. • Supply voltage above 20 V Travel operation is suspended for the duration of the undervoltage. The output current will be set to zero. When the supply voltage falls below 20 V, travel operation restarts. • Overtemperature warning The maximum stepping speed is reduced to 300 Hz. This ensures a safe shut-off procedure if the temperature increases to shut-off temperature. • 14 Overtemperature shut-off ATA6830 4575C–BCD–05/03 ATA6830 Travel operation is suspended when overtemperature is detected. An error signal is sent to the bus master via the bus. Operation can only restart after the supply voltage is shut off. • Interruption of a stepping motor winding The motor windings are only checked for interruption when supplied with hold current, not during drive operation. The corresponding output is shut off. The other coil winding is supplied with hold current. An error signal is sent. Operation can only restart after the supply voltage is shut off. • Short circuit of a stepping motor winding The corresponding output is shut off. The other coil winding is supplied with hold current. An error signal is sent. Operation can only restart after the supply voltage is shut off. • Short circuit of an output to ground or VBAT The corresponding output is shut off. The other coil winding is supplied with hold current. An error signal is sent. Operation can only restart after the supply voltage is shut off. An error signal is sent to the microcontroller by clamping the bus to ground for 3 seconds. If the error should occur during a data transmission, the above described reactions will happen immediately except for the clamping. This will take place about 200 µs after the end of the stopbit of the lowbyte to guarantee a correct command recognintion in the second headlamp. The error signal timing is shown in Figure 15. Figure 15. Error Signal Timing MESSAGE FRAME ERROR RESPONSE ca. 9.2 ms 3s 1 Buslevel 0 Absolute Maximum Ratings Parameters Symbol Value Unit Power supply (t < 400 ms) VBAT -0.3 to +45 V DC power supply VBAT -0.3 to +28 V DC output current IOUT ±1.1 A BUS input voltage VBUS -0.3 to VBAT +0.3 V Human body model ESD 2 kV Charged device model ESD 500 V Storage temperature TStg -55 to +150 °C Operating temperature Top -40 to +105 °C Tjmax +150 °C Maximum junction temperature 15 4575C–BCD–05/03 Thermal Resistance Parameters Symbol Value Unit Thermal resistance junction-case RthJC 5 K/W Thermal resistance junction-ambient RthJA 35 K/W Symbol Value Unit Operating Range Parameters Power supply range Operating temperature range VBAT 7 to 20 V Top -40 to +105 °C Electrical Characteristics No. 1 1.1 1.2 Parameters Test Conditions Pin Symbol Supply current VBAT = 14 V (no motor current) 1, 7, 15, 21 I_total Supply voltage Normal operation 1, 7, 15, 21 VBATsup 7.0 23 VVDD_13V 4.9 VBAT = 7.0 V 23 VVDD_7V Threshold voltage VBAT = 12.0 V, rising edge 22 Threshold voltage VBAT = 12 V, falling edge VDD voltage 1.4 VDD voltage 2.1 2.2 Typ. Max. Unit Type* 4 7 mA A 20 V C 5.0 5.1 V A 4.8 5.0 5.1 V A VLH_BUS_12 5.5 6.5 7.5 V A 22 VHL_BUS_12 4.5 5.5 6.5 V A V A -400 -300 -220 µA A 0.5 V A mA A Supply 1.3 2 Min. Bus Port 2.3 Hysteresis 22 VHYS_BUS12 2.4 Input current VBUS = 0 V 22 IOUT_BUS_8 Saturation voltage IBUS = 2 mA, bus clamping 22 VSAT_BUS_7 Pulldown current At error condition 22 IPulldwn_7 2 COS = 100 pF ±5% RSET = 20 kW ±1% 27 FOSC_13 340 400 460 kHz A Reference voltage RSET = 20 kW ±1% 26 VRSET_13V 2.4 2.5 2.6 V A Reference voltage VBAT = 7 V 26 VRSET_7V 2.3 2.5 2.6 V A 3, 5, 17, 20 RDSon 1.2 1.7 W B 2.5 2.6 3 3.1 4 4.1 4.2 5 5.1 1 Oscillator Frequency Reference Full Bridges RDSON RDSON of half-bridge *) Type means: A = 100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter Note: 1. cmd = command 16 ATA6830 4575C–BCD–05/03 ATA6830 Electrical Characteristics (Continued) No. Parameters Test Conditions Pin Symbol Max. Unit Type* 5.2 Output current Output stage off 3, 5, 17, 20 ILEAK 10 µA A 5.3 Output current Hold mode RSHUNT = 240 mW 3, 5, 17, 20 VSHUNT18 40 55 200 mA B 5.4 Output current Test mode RSHUNT = 240 mW 3, 5, 17, 20 VSHUNT99 240 300 360 mA B 5.5 Output current Normal mode RSHUNT = 240 mW 3, 5, 17, 20 VSHUNT182 500 550 600 mA B 5.6 Output current Normal mode (T