TMC2300-LA-T

POWER DRIVER FOR STEPPER MOTORS INTEGRATED CIRCUITS TMC2300 Datasheet Low Voltage Driver for Two-Phase Stepper Motors up to 1.2A RMS - StealthChop™ for Quiet Movement - UART Interface Option. With StallGuard Sensorless Homing and CoolStep Energy Saving. APPLICATIONS 4 FEATURES AND BENEFITS Voltage Range 2V (1.8V) … 11V DC Battery Operation min. 2 AA / NiMh cells, or 1-2 Li-Ion cells 2-phase Stepper Motors up to 1.2A RMS, 2A peak Standby 100µF electrolytic / depending on supply resistance and motor current OA1 Stand Still Current Reduction Step Pulse Generator STEPPER +VM VS Step&Dir input DIR AD0 UART Address setting 1n-100n 10V TMC2300 MicroPlyer Step and Direction motion control VCP 100n Optional external capacitor 1.8VOUT Place near IC with short path to die pad StealthChop2 current controller S N stepper motor RSA BRA Connect directly to GND plane BRB Use low inductivity SMD type for R SA and RSB OB1 CoolStep Full Bridge B OB2 StallGuard4 STANDBY BRB 500k RSB CLK oscillator GND +VIO DIE PAD EN Connect directly to GND plane opt. driver enable Figure 1.1 TMC2300 basic application block diagram for stepper motors MODES OF OPERATION: OPTION 1: Standalone stepper STEP/DIR Driver (Legacy Mode) A CPU (µC) generates step & direction signals. The TMC2300 operates the motor as commanded by the configuration pins and STEP/DIR signals. Motor run current is fixed by sense resistor setting. The pin PDN_UART selects automatic standstill current reduction. Feedback from the driver to the CPU is granted by the DIAG output signal. Enable or disable the motor using the EN pin and VIO/NSTANDBY pin. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 5 STANDALONE STEP/DIR STEPPER DRIVER OA1 S/D ERROR TMC2300 S OA2 N OB1 OB2 Figure 1.2 Stand-alone driver OPTION 2: STEP/DIR Driver with Full Diagnostics and Control Similar to Option 1, but pin PDN_UART is connected to the CPU UART interface. UART Additional options (label UART): + + + + + + + CoolStep energy saving StallGuard sensorless homing Detailed diagnostics and thermal management Passive braking and freewheeling for flexible, lowest power stop modes More options for microstep resolution setting (fullstep to 256 microstep) Software controlled motor current setting and more chopper options Option for motion using internal pulse generator (no STEP/DIR signals required) UART INTERFACE FOR FULL DIAGNOSTICS AND CONTROL OA1 S/D High-Level Interface CPU UART TMC2300 OA2 S N OB1 OB2 Figure 1.3 STEP/DIR Driver with UART This mode allows replacing all control lines like ENN, DIAG, MS1, MS2 by a single interface line. This way, only three signals are required for full control: STEP, DIR and PDN_UART. Even motion without external STEP pulses is provided by an internal programmable step pulse generator: Just set the desired motor velocity. However, no ramping is provided by the TMC2300. Access to multiple driver ICs is possible using 4 different address settings or via an analog multiplexer IC. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 6 1.1 Key Concepts The TMC2300 implements advanced features which are exclusive to TRINAMIC products. These features contribute toward greater precision, greater energy efficiency, higher reliability, smoother motion, and cooler operation in many stepper motor applications. StealthChop2™ No-noise, high-precision chopper algorithm for inaudible motion and inaudible standstill of the motor. Allows faster motor acceleration and deceleration than StealthChop™ and extends StealthChop to low stand still motor currents. StallGuard™ Sensorless motor load measurement. It allows sensorless homing of a drive by sensing mechanical obstacles. Further, mechanics can be validated by monitoring motor load. MicroPlyer™ Microstep interpolator for obtaining full 256 microstep smoothness with lower resolution step inputs starting from fullstep CoolStep™ Uses StallGuard measurement in order to adapt the motor current for best efficiency and lowest heat-up of motor and driver In addition to these performance enhancements, TRINAMIC motor drivers offer safeguards to detect and protect against shorted outputs, output open-circuit, overtemperature, and undervoltage conditions for enhancing safety and recovery from equipment malfunctions. 1.2 Control Interfaces The TMC2300 supports both, discrete control lines for basic mode selection and a UART based single wire interface with CRC checking. 1.2.1 UART Interface UART The single wire interface allows unidirectional operation (for parameter setting only), or bi-directional operation for full control and diagnostics. It can be driven by any standard microcontroller UART or even by bit banging in software. Baud rates from 9600 Baud to 500k Baud may be used. No baud rate configuration is required, as the TMC2300 automatically adapts to the masters’ baud rate. The frame format is identical to the intelligent TRINAMIC controller & driver ICs TMC51XX and TMC22XX. A CRC checksum allows data transmission over longer distance. For fixed initialization sequences, store the data including CRC into the µC, thus consuming only a few 100 bytes of code for a full initialization. CRC may be ignored during read access, if not desired. This makes CRC use an optional feature! The IC has a fixed address selected by 2 pins. Multiple drivers can be programmed in parallel by tying together all interface pins, in case no read access is required. An optional addressing can be provided by analog multiplexers, like 74HC4066. From a software point of view the TMC2300 is a peripheral with a number of control and status registers. Most of them can either be written only or are read only. Some of the registers allow both, read and write access. In case read-modify-write access is desired for a write only register, a shadow register can be realized in master software. 1.3 Moving and Controlling the Motor 1.3.1 STEP/DIR Interface The motor is controlled by a step and direction input. Active edges on the STEP input can be rising edges or both rising and falling edges as controlled by a special mode bit (DEDGE). Using both edges cuts the toggle rate of the STEP signal in half, which is useful for communication over slow interfaces such as optically isolated interfaces. The state sampled from the DIR input upon an active STEP edge determines whether to step forward or back. Each step can be a fullstep or a microstep, in which there are 2, 4, 8, 16, 32, 64, 128, or 256 microsteps per fullstep. A step impulse with a low state on DIR increases the microstep counter and a high state decreases the counter by an amount controlled www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 7 by the microstep resolution. An internal table translates the counter value into the sine and cosine values which control the motor current for microstepping. 1.3.2 Internal Step Pulse Generator UART Some applications do not require a precisely co-ordinated motion – the motor just is required to move until a certain event occurs, or a certain distance is passed. The TMC2300 comes with an internal pulse generator for these applications: Just provide the velocity via UART interface to move the motor. The velocity sign automatically controls the direction of the motion. This way, the motor will move without processor pulse generation. The processor just needs to terminate motion, when the target is reached, e.g. by polling the microstep counter. However, the pulse generator does not integrate a ramping function. Motion at higher velocities will require ramping up and ramping down the velocity value via software. STEP/DIR mode and internal pulse generator mode can be mixed in an application! 1.4 StealthChop2 Driver StealthChop is a voltage chopper-based principle. It is optimum especially for low voltage operation, because microstepping sine waves are generated even at 100% duty cycle. It especially guarantees that the motor is absolutely quiet in standstill and in slow motion, except for noise generated by bearings. Unlike other voltage mode choppers, StealthChop2 does not require any configuration. It automatically learns the best settings during the first motion after power up and further optimizes the settings in subsequent motions. An initial homing sequence is sufficient for learning. StealthChop2 allows high motor dynamics, by reacting at once to a change of motor velocity. Benefits of using StealthChop2: - Significantly improved microstepping with low cost motors - Motor runs smooth and quiet - Absolutely no standby noise - Reduced mechanical resonance yields improved torque 1.5 StallGuard4 – Load Sensing UART StallGuard4 provides an accurate measurement of the load on the motor. It can be used for stall detection as well as other uses at loads below those which stall the motor, such as CoolStep loadadaptive current reduction. This gives more information on the drive, allowing functions like sensorless homing and diagnostics of the drive mechanics. 1.6 CoolStep – Load Adaptive Current UART CoolStep drives the motor at the optimum current. It uses the StallGuard4 load measurement information to adjust the motor current to the minimum amount required in the actual load situation. This saves energy and keeps the components cool. Benefits are: - Energy efficiency - Motor generates less heat - Less or no cooling - Use of smaller motor - Less motor noise power consumption decreased up to 90% (w. no load on motor) improved mechanical precision improved reliability less torque reserve required → cheaper motor does the job Due to less energy exciting motor resonances Figure 1.4 shows the efficiency gain of a 42mm stepper motor when using CoolStep compared to standard operation with 50% of torque reserve. coolStep is enabled above 60RPM in the example. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 8 0,9 Efficiency with coolStep 0,8 Efficiency with 50% torque reserve 0,7 0,6 0,5 Efficiency 0,4 0,3 0,2 0,1 0 0 50 100 150 200 250 300 350 Velocity [RPM] Figure 1.4 Energy efficiency with coolStep (example) 1.7 Automatic Standstill Power Down An automatic current reduction drastically reduces application power dissipation and cooling requirements. Per default, the stand still current reduction is enabled by pulling PDN_UART input to GND. It reduces standstill power dissipation to less than 33% by going to slightly more than half of the run current. Modify stand still current, delay time and decay via UART. Automatic freewheeling and passive motor braking are provided as an option for stand still. Passive braking reduces motor standstill power consumption to zero, while still providing effective dampening and braking! STEP CURRENT IRUN IHOLD RMS motor current trace with pin PDN=0 TPOWERDOWN IHOLDDELAY power down power down ramp time delay time t Figure 1.5 Automatic Motor Current Power Down 1.8 Index Pulse UART The index output gives one pulse per electrical rotation, i.e. one pulse per each four fullsteps. It shows the internal sequencer microstep 0 position (MSTEP near 0). This is the power on position. In combination with a mechanical home switch, a more precise homing is enabled. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 2 9 Pin Assignments The TMC2300 comes in a tiny package in order to fit miniaturized devices. For the ease of use, pinning is shown separately for both function-modes. 11 12 13 17 16 TMC2300 (Standalone Stepper) © B. Dwersteg, TRINAMIC PAD 6 7 8 9 14 14 MS2_AD1 EN STEPPER MODE PDN_UART 10 5 9 4 5 8 3 4 7 2 3 6 OA2 VCP DIR STEP MS1 18 1 2 TMC2300 (UART Stepper) © B. Dwersteg, TRINAMIC PAD OB2 GND 1.8VOUT DIAG VIO/NSTDBY 19 15 20 13 16 12 17 OB2 GND 1.8VOUT DIAG VIO/NSTDBY 10 MS2 EN STEPPER MODE PDN 18 1 OA2 VCP DIR STEP MS1_AD0 19 15 20 11 BRA OA1 VS OB1 BRB BRA OA1 VS OB1 BRB 2.1 Package Outline TMC2300 Figure 2.1 TMC2300 Pinning Top View Stepper Driver – QFN20, 3x3mm², 0.4mm pitch 2.2 Signal Descriptions / Stepper modes Pin OA2 Number 1 VCP 2 DIR 3 DI STEP MS1_AD0 4 5 DI DI MS2_AD1 6 DI EN 7 DI STEPPER 8 DI MODE 9 DI PDN_UART 10 DIO VIO/NSTDBY 11 DIAG 12 www.trinamic.com Type DO Function Motor coil A output 2 Charge pump voltage. Optionally tie to VS using 1nF to 100nF capacitor. May be left unconnected. DIR input (Analog test output in factory test mode) STEP input Microstep resolution configuration MS2, MS1: 00: 1/8, 01: 1/32, 10: 1/64, 11: 1/16 For UART based configuration selection of UART Address 0…3 (AD0=LSB, AD1=MSB) Enable input. The power stage becomes switched off (all motor outputs floating) when this pin becomes driven to a low level. Also used to clear error flags. Mode selection input. STEPPER, MODE: 00: do not use 01: do not use 10: Stepper 11: Standalone Stepper (CLK, TST input in factory test mode) UART Input/Output. In standalone mode: Inverted power-down control input (low = automatic standstill current reduction). 1.8V to 5V IO supply voltage for all digital pins. IC goes to standby mode and resets, when this pin is pulled to GND. Diagnostic output. High level upon driver error or stall. Reset by EN=low. TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) Pin Number 1.8VOUT 13 GND OB2 14 15 BRB 16 OB1 17 VS 18 OA1 19 BRA 20 Exposed die pad - www.trinamic.com Type 10 Function Output of internal 1.8V regulator. Attach 100nF ceramic capacitor to GND near to pin for best performance. Provide the shortest possible loop to the GND pad. GND. Connect to GND plane near pin. Motor coil B output 2 Sense resistor connection for coil B. Place sense resistor to GND near pin. Motor coil B output 1 Motor supply voltage. Provide filtering capacity >10µF near pin with shortest possible loop to GND pad. Motor coil A output 1 Sense resistor connection for coil A. Place sense resistor to GND near pin. Connect the exposed die pad to a GND plane. Provide as many as possible vias for heat transfer to GND plane. TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 3 11 Sample Circuits The sample circuits show the connection of external components in different operation and supply modes. The connection of the bus interface and further digital signals is left out for clarity. The TMC2300 is configured for different application modes by two pins, as well as by settings available via the UART interface. STEPPER/MODE: CONFIGURATION OF OPERATION MODE STEPPER VCC_IO VCC_IO MODE GND VCC_IO Operation Mode UART controlled stepper driver, MS1 and MS2 select the UART address. Standalone Stepper. Set power down mode using PDN, and microstep resolution using MS1 and MS2. 3.1 Standard Application Circuit STEP AD1 Configuration Interface STEPPER MODE UART interface Driver error / Index pulse / Stall 1.8V to 5V I/O voltage / standby B. Dwersteg, © TRINAMIC 2016 UART UART interface + Register Block DIAG Programmable Diagnostic Output VIO/ NSTDBY 100n Standby detector +VM 100n Internal charge pump STANDBY Full Bridge A OA2 BRA 256 Microstep Sequencer 10µ Or low ESR >100µF electrolytic / depending on supply resistance and motor current OA1 Stand Still Current Reduction Step Pulse Generator AD0 UART Address setting 1.8V Voltage regulator Step&Dir input DIR 1n-100n 10V VS TMC2300 MicroPlyer Step and Direction motion control VCP 100n Optional external capacitor 1.8VOUT Place near IC with short path to die pad StealthChop2 current controller S N stepper motor RSA BRA Connect directly to GND plane BRB Use low inductivity SMD type for R SA and RSB OB1 CoolStep Full Bridge B OB2 StallGuard4 STANDBY BRB 500k RSB CLK oscillator GND +VIO DIE PAD EN Connect directly to GND plane opt. driver enable Figure 3.1 Standard Application Circuit for 2V to 11V Supply The standard application circuit uses a minimum set of additional components to operate a stepper motor. Two sense resistors set the motor coil current. See chapter 8 to choose the right sense resistors. Take care to keep power supply ripple due to chopper operation at a few 100mV, max., especially when low voltage operation is desired. Use a ceramic, or low ESR capacitors for filtering the power supply. The capacitors need to cope with the current ripple caused by chopper operation. A minimum capacity of 100µF electrolytic, or 10µF ceramic capacitor near the driver is recommended to keep ripple low. Actual demand will depend on the internal power supply resistance and the desired motor current. VCC_IO can be supplied from a separate supply, e.g. a 3.3V regulator, or be driven by a microcontroller port pin. AD0 and AD1 set the UART address. A charge pump capacitor can be added for slightly reduced power dissipation when operating near the lower voltage limit of roughly 2V. Basic layout and component hints Place sense resistors and all filter capacitors as close as possible to the related IC pins. Use a solid common GND for all GND connections, also for sense resistor GND. Connect 1.8VOUT filtering capacitor directly to 1.8VOUT and the GND pin. See layout hints for more details. Low ESR electrolytic capacitors are recommended for VS filtering unless supply resistance is very low. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 12 3.2 Standalone Stepper STEP Step and Direction motion control VCP 100n 1.8VOUT Place near IC with short path to die pad 1.8V Voltage regulator Step&Dir input 100n Internal charge pump STANDBY 10µ Full Bridge A OA2 S MS1 MS2 MODE Disable standstill current reduction B. Dwersteg, © TRINAMIC 2016 PDN StealthChop2 current controller Standby detector N stepper motor RSA BRA Connect directly to GND plane BRB Use low inductivity SMD type for R SA and RSB OB1 Driver Error VIO/ NSTDBY 100n 256 Microstep Sequencer Power down DIAG Driver error BRA Configuration Interface STEPPER MicroPlyer Microstep Resolution (GND or VIO) Or low ESR >100µF electrolytic / depending on supply resistance and motor current OA1 Stand Still Current Reduction 1.8V to 5V I/O voltage / standby +VM VS TMC2300 DIR No capacitor required Full Bridge B OB2 STANDBY BRB 500k RSB CLK oscillator GND +VIO DIE PAD EN Connect directly to GND plane opt. driver enable Figure 3.2 Standalone Stepper Operation The standalone stepper application uses just three interface lines, to operate the stepper: STEP, DIR and DIAG for feedback. Microstep resolution and standstill power down become pre-configured by tying MS1, MS2 and PDN to VIO or GND. The motor current is determined by the choice of sense resistors. 3.2.1 Configuration Pins The TMC2300 provides three configuration pins. These pins allow quick configuration for standalone operation. PDN_UART: CONFIGURATION OF STANDSTILL POWER DOWN (STANDALONE STEPPER MODE) PDN_UART GND VIO UART interface Current Setting Enable automatic power down in standstill periods Disable automatic power down When using the UART interface, the power-down configuration pin is automatically disabled. Program IHOLD as desired for standstill periods. MS1/MS2: CONFIGURATION OF MICROSTEP RESOLUTION FOR STEP INPUT (STANDALONE STEPPER MODE) MS2 GND GND VIO VIO MS1 GND VIO GND VIO www.trinamic.com Microstep Setting 8 microsteps 32 microsteps 64 microsteps 16 microsteps TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 13 3.3 Highly Efficient Driver The TMC2300 integrates a highly efficient power stage, offering low RDSon even at low supply voltages, due to its internal charge pump. This enables high motor current drive capability and low power dissipation for battery powered applications. RDSon vs. VS 400,00 350,00 300,00 250,00 200,00 150,00 100,00 50,00 0,00 1,5 2,0 2,5 RDSon (LS) [mOhm] 3,0 3,5 4,0 RDSon(HS) [mOhm] Figure 3.3 RDSon Variation over Supply Voltage When operating at a high motor current, the driver power dissipation due to MOSFET switch onresistance significantly heats up the driver. This power dissipation will significantly heat up the PCB cooling infrastructure, if operated at an increased duty cycle. This in turn leads to a further increase of driver temperature. An increase of temperature by about 100°C increases MOSFET resistance by roughly 50%. This is a typical behavior of MOSFET switches. Therefore, under high duty cycle, high load conditions, thermal characteristics have to be carefully taken into account, especially when increased environment temperatures are to be supported. Refer the thermal characteristics and the layout hints for more information. As a thumb rule, thermal properties of the PCB design become critical for the tiny QFN 3mm x 3mm package at or above 0.8A RMS motor current for increased periods of time. For currents above 0.8A, a 4-layer PCB layout with 5 via contact of the die attach pad to the GND plane is required. Keep in mind that resistive power dissipation raises with the square of the motor current. On the other hand, this means that a small reduction of motor current significantly saves heat dissipation and energy. Pay special attention to good thermal properties of your PCB layout, when going for 0.8A RMS current or more. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 14 3.4 Low Power Standby Battery powered applications, as well as mains powered applications conforming to EU energy saving regulations, often require a standby mode, where the power-supply remains on. Current consumption in this mode must be minimized. Control near zero power TMC2300 standby operation by switching off the I/O supply voltage on VIO_NSTDBY pin. At the same time make sure, that no digital input pin is at a high level. An input level above VIO_NSTDBY would hinder pulling down VIO_NSTDBY, due to the ESD protection diodes in each digital I/O pin. These diodes clamp each input to a level between GND and the IO supply voltage VIO_NSTDBY. Therefore, stop the motor first, and allow sufficient time for the motor to come to a standstill, pull the enable input EN low, and also all other input pins, to switch off the motor completely before switching off VIO voltage. All driver registers are reset to their power-up defaults after leaving standby mode. See Figure 3.4. Operation Actual Power Draw Low current standby Standstill 0) %01: Freewheeling %10: Coil shorted using LS drivers (passive braking) %11: Coil shorted using HS drivers (passive braking) 0 Fixed value for PWM_GRAD (PWM_GRAD_AUTO = PWM_GRAD) 1 Automatic tuning (only with pwm_autoscale=1) PWM_GRAD_AUTO is initialized with PWM_GRAD and becomes optimized automatically during motion. Preconditions 1. PWM_OFS_AUTO has been automatically initialized. This requires standstill at IRUN for >130ms in order to a) detect standstill b) wait > 128 chopper cycles at IRUN and c) regulate PWM_OFS_AUTO so that -1 < PWM_SCALE_AUTO < 1 2. Motor running and 1.5 * PWM_OFS_AUTO < PWM_SCALE_SUM < 4* PWM_OFS_AUTO and PWM_SCALE_SUM < 255. Time required for tuning PWM_GRAD_AUTO About 8 fullsteps per change of +/-1. 0 User defined feed forward PWM amplitude. The current settings IRUN and IHOLD have no influence! The resulting PWM amplitude (limited to 0…255) is: PWM_OFS * ((CS_ACTUAL+1) / 32) + PWM_GRAD * 256 / TSTEP TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 30 0X70: PWMCONF – VOLTAGE MODE PWM STEALTHCHOP Bit Name Function 17 16 pwm_freq1 pwm_freq0 PWM frequency selection 15 14 13 12 11 10 9 8 PWM_ GRAD User defined amplitude gradient 7 6 5 4 3 2 1 0 PWM_ OFS User defined amplitude (offset) Comment 1 Enable automatic current control (Reset default) Set to zero (for a short time) in order to force a new initialization of PWM_OFS_AUTO=PWM_OFS and PWM_GRAD_AUTO=PWM_GRAD. %00: fPWM=2/1024 fCLK %01: fPWM=2/683 fCLK %10: fPWM=2/512 fCLK %11: fPWM=2/410 fCLK Velocity dependent gradient for PWM amplitude: PWM_GRAD * 256 / TSTEP This value is added to PWM_AMPL to compensate for the velocity-dependent motor back-EMF. (Reset default=16) With automatic scaling (pwm_autoscale=1) the value is used for first initialization, only. Set PWM_GRAD to the application specific value (it can be read out from PWM_GRAD_AUTO) to speed up the automatic tuning process. User defined PWM amplitude offset (0-255) related to full motor current (CS_ACTUAL=31) in stand still. (Reset default=36) When using automatic scaling (pwm_autoscale=1) the value is used for initialization, only. The autoscale function starts with PWM_SCALE_AUTO=PWM_OFS and finds the required offset to yield the target current automatically. PWM_OFS = 0 will disable scaling down motor current below a motor specific lower measurement threshold. This setting should only be used under certain conditions, i.e. when the power supply voltage can vary up and down by a factor of two or more. It prevents the motor going out of regulation, but it also prevents power down below the regulation limit. PWM_OFS > 0 allows automatic scaling to low PWM duty cycles even below the lower regulation threshold. This allows low (standstill) current settings based on the actual (hold) current scale (register IHOLD_IRUN). www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 5.5.3 31 DRV_STATUS – Driver Status Flags 0X6F: DRV_STATUS – DRIVER STATUS FLAGS AND CURRENT LEVEL READ BACK Bit 31 Name stst Function standstill indicator 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 - reserved Comment This flag indicates motor stand still in each operation mode. This occurs 2^20 clocks after the last step pulse. Ignore these bits - reserved Ignore these bits CS_ ACTUAL actual motor current / smart energy current Actual current control scaling, for monitoring the function of the automatic current scaling. - reserved Ignore these bits - 0 Ignore these bits t150 t120 olb 6 ola 5 s2vsb 4 s2vsa 150°C comparator 120°C comparator open load indicator phase B open load indicator phase A low side short indicator phase B low side short indicator phase A 3 s2gb 2 s2ga 1 ot 0 otpw 1: Temperature threshold is exceeded, driver is off 1: Temperature prewarning threshold is exceeded 1: Open load detected on phase A or B. Hint: This is just an informative flag. The driver takes no action upon it. False detection may occur in fast motion and standstill. Check during slow motion, only. 1: Short on low-side MOSFET detected on phase A or B. The driver becomes disabled. The flags stay active, until the driver is disabled by software (enabledrv=0) or by the ENN input. Flags are separate for both chopper modes. 1: Short to GND detected on phase A or B. The driver becomes disabled. The flags stay active, until the driver is disabled by software (enabledrv=0) or by the ENN input. 1: The overtemperature limit has been reached. Drivers become disabled until otpw is also cleared due to cooling down of the IC. The overtemperature flag is common for both bridges. 1: The overtemperature pre-warning threshold is exceeded. The overtemperature pre-warning flag is common for both bridges. www.trinamic.com short to ground indicator phase B short to ground indicator phase A overtemperature flag overtemperature prewarning flag TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 6 32 StealthChop™ StealthChop is an extremely quiet mode of operation for stepper motors. It is based on a voltage mode PWM. In case of standstill and at low velocities, the motor is absolutely noiseless. Thus, StealthChop operated stepper motor applications are very suitable for indoor or home use. The motor operates absolutely free of vibration at low velocities. With StealthChop, the motor current is applied by driving a certain effective voltage into the coil, using a voltage mode PWM. With the enhanced StealthChop2, the driver automatically adapts to the application for best performance. No more configurations are required. Optional configuration allows for tuning the setting in special cases, or for storing initial values for the automatic adaptation algorithm. Figure 6.1 Motor coil sine wave current with StealthChop (measured with current probe) 6.1 Automatic Tuning StealthChop2 integrates an automatic tuning procedure (AT), which adapts the most important operating parameters to the motor automatically. This way, StealthChop2 allows high motor dynamics and supports powering down the motor to very low currents. Just two steps have to be respected by the motion controller for best results: Start with the motor in standstill, but powered with nominal run current (AT#1). Move the motor at a medium velocity, e.g. as part of a homing procedure (AT#2). Figure 6.2 shows the tuning procedure. Border conditions in for AT#1 and AT#2 are shown in the following table: AUTOMATIC TUNING TIMING AND BORDER CONDITIONS Step AT#1 Parameter PWM_ OFS_AUTO AT#2 PWM_ GRAD_AUTO www.trinamic.com Conditions - Motor in standstill and actual current scale (CS) is identical to run current (IRUN). - If standstill reduction is enabled (pin PDN_UART=0), an initial step pulse switches the drive back to run current. - Pin VS at operating level. - Motor must move at a velocity, where a significant amount of back EMF is generated and where the full run current can be reached. Conditions: - 1.5 * PWM_OFS_AUTO < PWM_SCALE_SUM < 4 * PWM_OFS_AUTO - PWM_SCALE_SUM < 255. Hint: A typical range is 60-300 RPM. Determine best conditions with the evaluation board and monitor PWM_SCALE_AUTO going down to zero during tuning. Duration ≤ 2^20+2*2^18 tCLK, ≤ 130ms (with internal clock) 8 fullsteps are required for a change of +/-1. For a typical motor with PWM_GRAD_AUTO optimum at 64 or less, up to 400 fullsteps are required. TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 33 Power Up PWM_GRAD_AUTO becomes initialized with 16 Driver Enabled? N Y Stand still N Y N AT#1 Driver Enabled? Standstill reduction enabled? Y Issue (at least) a single step pulse and stop again, to power motor to run current stealthChop2 regulates to nominal current and stores result to PWM_OFS_AUTO (Requires stand still for >130ms) Move the motor, e.g. for homing. Include a constant, medium velocity ramp segment. AT#2 Homing Ready stealthChop2 regulates to nominal current and optimizes PWM_GRAD_AUTO (requires 8 fullsteps per change of 1, typically a few 100 fullsteps in sum) stealthChop2 settings are optimized! Option with UART Store PWM_GRAD_AUTO for faster tuning procedure stealthChop2 keeps tuning during subsequent motion and stand still periods adapting to motor heating, supply variations, etc. Figure 6.2 StealthChop2 automatic tuning procedure Attention with varying supply voltage: Modifying the supply voltage VS invalidates the result of the automatic tuning process. However, automatic tuning adapts to changed conditions whenever AT#1 and AT#2 conditions are fulfilled. This is no problem with sinking supply voltage, i.e. due to the battery running low, as the regulator corrects by increasing the PWM value. However, with an increasing supply voltage, motor current rises, as the lower regulator limit is given by the result of the las AT#1 phase. Take this into account, when experimenting with a lab supply and modifying supply voltage. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 34 6.2 StealthChop Options UART In order to match the motor current to a certain level, the effective PWM voltage becomes scaled depending on the actual motor velocity. Several additional factors influence the required voltage level to drive the motor at the target current: The motor resistance, its back EMF (i.e. directly proportional to its velocity) as well as the actual level of the supply voltage. Two modes of PWM regulation are provided: The automatic tuning mode (AT) using current feedback (pwm_autoscale = 1, pwm_autograd = 1) and a feed forward velocity-controlled mode (pwm_autoscale = 0). The feed forward velocitycontrolled mode will not react to a change of the supply voltage or to events like a motor stall, but it provides very stable amplitude. It does not use nor require any means of current measurement. This is perfect when motor type and supply voltage are well known. Therefore, we recommend the automatic mode, unless current regulation is not satisfying in the given operating conditions. It is recommended to operate in automatic tuning mode. Non-automatic mode (pwm_autoscale=0) should be taken into account only with well-known motor and operating conditions. In this case, programming via the UART interface is required. The operating parameters PWM_GRAD and PWM_OFS can be determined in automatic tuning mode initially. The StealthChop PWM frequency can be chosen in four steps in order to adapt the chopper frequency to the motor inductance. It balances low current ripple and good higher velocity performance vs. increased dynamic power dissipation at higher frequency. CHOICE OF PWM FREQUENCY Clock frequency fCLK PWM_FREQ=%00 fPWM=2/1024 fCLK 12MHz (typ. value) 23.4kHz PWM_FREQ=%01 fPWM=2/683 fCLK (default) 35.1kHz PWM_FREQ=%10 fPWM=2/512 fCLK PWM_FREQ=%11 fPWM=2/410 fCLK 46.9kHz 58.5kHz Table 6.1 Choice of PWM frequency – green / light green: recommended 6.3 StealthChop Current Regulator In StealthChop voltage PWM mode, the autoscaling function (pwm_autoscale = 1, pwm_auto_grad = 1) regulates the motor current to the desired current setting. Automatic scaling is used as part of the automatic tuning process (AT), and for subsequent tracking of changes within the motor parameters. The driver measures the motor current during the chopper on time and uses a proportional regulator to regulate PWM_SCALE_AUTO in order match the motor current to the target current. PWM_REG is the proportionality coefficient for this regulator. Basically, the proportionality coefficient should be as small as possible in order to get a stable and soft regulation behavior, but it must be large enough to allow the driver to quickly react to changes caused by variation of the motor target current (e.g. change of VREF). During initial tuning step AT#2, PWM_REG also compensates for the change of motor velocity. Therefore, a high acceleration during AT#2 will require a higher setting of PWM_REG. With careful selection of homing velocity and acceleration, a minimum setting of the regulation gradient often is sufficient (PWM_REG=1). PWM_REG setting should be optimized for the fastest required acceleration and deceleration ramp (compare Figure 6.3 and Figure 6.4). The quality of the setting PWM_REG in phase AT#2 and the finished automatic tuning procedure (or non-automatic settings for PWM_OFS and PWM_GRAD) can be examined when monitoring motor current during an acceleration phase Figure 6.5. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 35 Figure 6.3 Scope shot: good setting for PWM_REG Figure 6.4 Scope shot: too small setting for PWM_REG during AT#2 Motor Current PWM scale Motor Velocity PWM reaches max. amplitude RMS current constant (IRUN) PW M_ Nominal Current (sine wave RMS) Stand still PWM scale PWM_OFS_(AUTO) ok ok O) UT (_A AD GR M_ PW GR (P AD W M_ (_A RE UT G O) du ok rin g AT #2 ok ) 255 Current may drop due to high velocity IHOLD PWM_OFS_(AUTO) ok 0 0 Figure 6.5 Successfully determined PWM_GRAD(_AUTO) and PWM_OFS(_AUTO) www.trinamic.com Time TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 36 Quick Start For a quick start, see the Quick Configuration Guide in chapter 15. 6.3.1 Lower Current Limit The StealthChop current regulator imposes a lower limit for motor current regulation. As the coil current can be measured in the shunt resistor during chopper on phase only, a minimum chopper duty cycle allowing coil current regulation is given by the blank time as set by TBL and by the chopper frequency setting. Therefore, the motor specific minimum coil current in StealthChop autoscaling mode rises with the supply voltage and with the chopper frequency. A lower blanking time allows a lower current limit. It is important for the correct determination of PWM_OFS_AUTO, that in AT#1 the run current set by the sense resistor and IRUN is well within the regulation range. Lower currents (e.g. for standstill power down) are automatically realized based on PWM_OFS_AUTO and PWM_GRAD_AUTO respectively based on PWM_OFS and PWM_GRAD with non-automatic current scaling. The freewheeling option allows going to zero motor current. Lower motor coil current limit for StealthChop2 automatic tuning: 𝐼𝐿𝑜𝑤𝑒𝑟 𝐿𝑖𝑚𝑖𝑡 = 𝑡𝐵𝐿𝐴𝑁𝐾 ∗ 𝑓𝑃𝑊𝑀 ∗ 𝑉𝑀 𝑅𝐶𝑂𝐼𝐿 With VM the motor supply voltage and RCOIL the motor coil resistance. ILower Limit can be treated as a thumb value for the minimum nominal IRUN motor current setting. EXAMPLE: A motor has a coil resistance of 5Ω, the supply voltage is 8.4V. With TBL=%01 and PWM_FREQ=%00, tBLANK is 24 clock cycles, fPWM is 2/(1024 clock cycles): 𝐼𝐿𝑜𝑤𝑒𝑟 𝐿𝑖𝑚𝑖𝑡 = 24 𝑡𝐶𝐿𝐾 ∗ 2 8.4𝑉 24 8.4𝑉 ∗ = ∗ = 78𝑚𝐴 1024 𝑡𝐶𝐿𝐾 5Ω 512 5Ω This means, the motor target current for automatic tuning must be 78mA or more, taking into account all relevant settings. Attention For automatic tuning, a lower coil current limit applies. The motor current in automatic tuning phase AT#1 must exceed this lower limit. ILOWER LIMIT can be calculated or measured using a current probe. Setting the motor run-current or hold-current below the lower current limit during operation by modifying IRUN and IHOLD is possible after successful automatic tuning. The lower current limit also limits the capability of the driver to respond to changes of VREF. 6.4 Velocity Based Scaling UART Velocity based scaling scales the StealthChop amplitude based on the time between each two steps, i.e. based on TSTEP, measured in clock cycles. This concept basically does not require a current measurement, because no regulation loop is necessary. A pure velocity-based scaling is available via UART programming, only, when setting pwm_autoscale = 0. The basic idea is to have a linear approximation of the voltage required to drive the target current into the motor. The stepper motor has a certain coil resistance and thus needs a certain voltage amplitude to yield a target current based on the basic formula I=U/R. With R being the coil resistance, U the supply voltage scaled by the PWM value, the current I results. The initial value for PWM_AMPL can be calculated: www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 𝑃𝑊𝑀_𝐴𝑀𝑃𝐿 = 37 374 ∗ 𝑅𝐶𝑂𝐼𝐿 ∗ 𝐼𝐶𝑂𝐼𝐿 𝑉𝑀 With VM the motor supply voltage and ICOIL the target RMS current The effective PWM voltage UPWM (1/SQRT(2) x peak value) results considering the 8 bit resolution and 248 sine wave peak for the actual PWM amplitude shown as PWM_SCALE: 𝑈𝑃𝑊𝑀 = 𝑉𝑀 ∗ 𝑃𝑊𝑀_𝑆𝐶𝐴𝐿𝐸 248 1 𝑃𝑊𝑀_𝑆𝐶𝐴𝐿𝐸 ∗ ∗ = 𝑉𝑀 ∗ 256 256 √2 374 With rising motor velocity, the motor generates an increasing back EMF voltage. The back EMF voltage is proportional to the motor velocity. It reduces the PWM voltage effective at the coil resistance and thus current decreases. The TMC2300 provides a second velocity dependent factor (PWM_GRAD) to compensate for this. The overall effective PWM amplitude (PWM_SCALE_SUM) in this mode automatically is calculated in dependence of the microstep frequency as: 𝑓𝑆𝑇𝐸𝑃 𝑓𝐶𝐿𝐾 With fSTEP being the microstep frequency for 256 microstep resolution equivalent and fCLK the clock frequency supplied to the driver or the actual internal frequency 𝑃𝑊𝑀_𝑆𝐶𝐴𝐿𝐸_𝑆𝑈𝑀 = 𝑃𝑊𝑀_𝑂𝐹𝑆 + 𝑃𝑊𝑀_𝐺𝑅𝐴𝐷 ∗ 256 ∗ As a first approximation, the back EMF subtracts from the supply voltage and thus the effective current amplitude decreases. This way, a first approximation for PWM_GRAD setting can be calculated: 𝑃𝑊𝑀_𝐺𝑅𝐴𝐷 = 𝐶𝐵𝐸𝑀𝐹 [ 𝑉 𝑓𝐶𝐿𝐾 ∗ 1.46 ] ∗ 2𝜋 ∗ 𝑟𝑎𝑑 𝑉𝑀 ∗ 𝑀𝑆𝑃𝑅 𝑠 CBEMF is the back EMF constant of the motor in Volts per radian/second (See chapter 7). MSPR is the number of microsteps per rotation, e.g. 51200 = 256µsteps multiplied by 200 fullsteps for a 1.8° motor. Motor current PWM scaling (PWM_SCALE_SUM) 255 PWM reaches max. amplitude Constant motor RMS current Nominal current (e.g. sine wave RMS) M_ PW AD GR Cur r (de ent dr p en ops mo d tor s on loa d) PWM_OFS 0 0 VPWMMAX Figure 6.6 Velocity based PWM scaling (pwm_autoscale=0) www.trinamic.com Velocity TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 38 Hint The values for PWM_OFS and PWM_GRAD can easily be optimized by tracing the motor current with a current probe on the oscilloscope. Alternatively, automatic tuning determines these values and they can be read out from PWM_OFS_AUTO and PWM_GRAD_AUTO. Hint Start the motor from standstill when switching on StealthChop the first time and keep it stopped for at least 128 chopper periods to allow StealthChop to do initial standstill current control. 6.5 Flags in StealthChop UART As StealthChop uses voltage mode driving, status flags based on current measurement respond slower, respectively the driver reacts delayed to sudden changes of back EMF, like on a motor stall. Attention A motor stall, or abrupt stop of the motion during operation in StealthChop can trigger an overcurrent condition. Depending on the previous motor velocity, and on the coil resistance of the motor, it significantly increases motor current for a time of several 10ms. With low velocities, where the back EMF is just a fraction of the supply voltage, there is no danger of triggering the short detection. When homing using StallGuard4 to stop the motor upon stall, this is basically avoided. 6.5.1 Open Load Flags In StealthChop mode, OLA and OLB show if the current regulation sees that the nominal current can be reached on both coils. - A flickering OLA or OLB can result from asymmetries in the sense resistors or in the motor coils. An interrupted motor coil leads to a continuously active open load flag for the coil. One or both flags are active, if the current regulation did not succeed in scaling up to the full target current within the last few fullsteps (because no motor is attached or a high velocity exceeds the PWM limit). With StealthChop, PWM_SCALE_SUM can be checked to detect the correct coil resistance. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 6.5.2 39 PWM_SCALE_SUM Informs about the Motor State Information about the motor state is available with automatic scaling by reading out PWM_SCALE_SUM. As this parameter reflects the actual voltage required to drive the target current into the motor, it depends on several factors: motor load, coil resistance, supply voltage, and current setting. Therefore, an evaluation of the PWM_SCALE_SUM value allows checking the motor operation point. When reaching the limit (255), the current regulator cannot sustain the full motor current, e.g. due to a drop in supply voltage. 6.6 Freewheeling and Passive Braking UART StealthChop provides different options for motor standstill. These options can be enabled by setting the standstill current IHOLD to zero and choosing the desired option using the FREEWHEEL setting. The desired option becomes enabled after a time period specified by TPOWERDOWN and IHOLD_DELAY. Current regulation becomes frozen once the motor target current is at zero current in order to ensure a quick startup. With the freewheeling options, both freewheeling and passive braking can be realized. Passive braking is an effective eddy current motor braking, which consumes a minimum of energy, because no active current is driven into the coils. However, passive braking will allow slow turning of the motor when a continuous torque is applied. Hint Operate the motor within your application when exploring StealthChop. Motor performance often is better with a mechanical load, because it prevents the motor from stalling due mechanical oscillations which can occur without load. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 40 PARAMETERS RELATED TO STEALTHCHOP Parameter PWM_LIM pwm_ autoscale pwm_ autograd Description Limiting value for limiting the current jerk when switching on StealthChop following a disable condition. Reduce the value to yield a lower current peak. Enable automatic current scaling using current measurement or use forward controlled velocity based mode. Enable automatic tuning of PWM_GRAD_AUTO Setting 0 … 15 Comment Upper four bits of 8 bit amplitude limit (Default=12) 0 1 Forward controlled mode Automatic scaling with current regulator disable, use PWM_GRAD from register instead enable fPWM=2/1024 fCLK fPWM=2/683 fCLK fPWM=2/512 fCLK fPWM=2/410 fCLK Results in 0.5 to 7.5 steps for PWM_SCALE_AUTO regulator per fullstep PWM_OFS=0 disables linear current scaling based on current setting 0 1 0 1 2 3 PWM_REG User defined PWM amplitude (gradient) for 1 … 15 velocity-based scaling or regulation loop gradient when pwm_autoscale=1. PWM_OFS User defined PWM amplitude (offset) for velocity- 0 … 255 based scaling and initialization value for automatic tuning of PWM_OFFS_AUTO. PWM_GRAD User defined PWM amplitude (gradient) for 0 … 255 velocity-based scaling and initialization value for automatic tuning of PWM_GRAD_AUTO. FREEWHEEL Stand still option when motor current setting is 0 zero (I_HOLD=0). The freewheeling option makes 1 the motor easy movable, while both coil short 2 options realize a passive brake. 3 PWM_SCALE Read back of the actual StealthChop voltage PWM -255 … _AUTO scaling correction as determined by the current 255 regulator. PWM_SCALE Allow monitoring of the automatic tuning and 0 … 255 _AUTO determination of initial values for PWM_OFS and PWM_OFS PWM_GRAD. _AUTO enabledrv General enable for the motor driver 0 1 TBL Comparator blank time. This time needs to safely 0 cover the switching event and the duration of the 1 ringing on the sense resistor. Choose a setting of 2 1 or 2 for typical applications. For higher 3 capacitive loads, 3 may be required. Lower settings allow StealthChop to regulate down to lower coil current values. PWM_FREQ PWM frequency selection. Use the lowest setting giving good results. The frequency measured at each of the chopper outputs is half of the effective chopper frequency fPWM. www.trinamic.com Normal operation Freewheeling Coil short via LS drivers Coil short cia HS drivers (read only) Scaling value becomes frozen when driver is disabled (read only) Driver off, all outputs hi-Z Driver enabled 16 tCLK 24 tCLK 32 tCLK 40 tCLK TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 7 41 Fitting the Motor Especially for low voltage operation, the motor should be carefully selected to give a good fit to the application’s mechanics, as well as available supply voltage and current. Therefore, it is important to understand the supply voltage requirement for a given motor. Both, the generation of a certain torque, and the ability to provide this torque at a desired velocity, require a motor specific voltage. These two components add up. Main relevant parameters for a stepper motor: Nominal (RMS) coil current Nominal coil resistance Rated coil voltage Holding torque at ICOILNOM ICOILNOM [A] RCOIL [Ω] UN = RCOIL * ICOILNOM [V] HoldingTorque [Nm] (sometimes specified instead of ICOILNOM) The specified motor torque is reached with the RMS ICOIL current in both motor coils, in order to build up the required magnetic field strength. A lower current will basically proportionally generate a lower torque, e.g. 70% of torque at 70% current. Even a reduction to 70% saves a lot of energy, because power dissipation goes with the square of the current. Thus, a motor with more reserves can offer better efficiency! With this, calculate the required supply voltage UBAT for motor stand still and slow motion, taking into account the driver’s power stage resistance plus 0.3V loss in the sense resistor: 𝑈𝐵𝐴𝑇 = (𝑅𝐶𝑂𝐼𝐿 + 2 ∗ 0.17Ω) ∗ 𝐼𝐶𝑂𝐼𝐿 ∗ √2 + 0.3𝑉 ICOIL is the RMS motor current which gives the desired torque. For higher velocity operation (more than a few electrical rotations per second), the motor specific back EMF constant CBEMF should be additionally taken into account (see below explanation). With this, the lowest feasible supply voltage for a given motor and a maximum velocity [RPM] calculates to: 𝑈𝐵𝐴𝑇 = 0.3𝑉 + ((𝑅𝐶𝑂𝐼𝐿 + 2 ∗ 0.17Ω) ∗ 𝐼𝐶𝑂𝐼𝐿 + 𝐻𝑜𝑙𝑑𝑖𝑛𝑔𝑇𝑜𝑟𝑞𝑢𝑒[𝑁𝑚] 2𝜋 ∗ 𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦[𝑅𝑃𝑀] ∗ ) ∗ √2 2 ∗ 𝐼𝐶𝑂𝐼𝐿𝑁𝑂𝑀 60 Adapt your motor to battery operation With most motor suppliers you have the chance to adapt the coil winding. This allows to trade in a lower motor voltage for battery operation versus higher motor current. E.g. a motor with a short, thick coil wire can work at a lower voltage, than the same motor with a long, thin coil wire, but it needs a higher current for the same torque. UNDERSTANDING THE BACK EMF CONSTANT OF A MOTOR The back EMF constant is the voltage a motor generates when turned with a certain velocity. Often motor datasheets do not specify this value, as it can be deducted from motor torque and coil current rating. Within SI units, the back EMF constant CBEMF has the same numeric value as the torque constant. For example, a motor with a torque constant of 1 Nm/A would have a CBEMF of 1V/rad/s. Turning such a motor with 1 rps (1 rps = 1 revolution per second = 6.28 rad/s) generates a back EMF voltage of 6.28V. Thus, the back EMF constant can be calculated as: 𝐶𝐵𝐸𝑀𝐹 [ 𝑉 𝐻𝑜𝑙𝑑𝑖𝑛𝑔𝑇𝑜𝑟𝑞𝑢𝑒[𝑁𝑚] ]= 𝑟𝑎𝑑/𝑠 2 ∗ 𝐼𝐶𝑂𝐼𝐿𝑁𝑂𝑀 [𝐴] ICOILNOM is the motor’s rated phase current for the specified holding torque HoldingTorque is the motor specific holding torque, i.e. the torque reached at ICOILNOM on both coils. The torque unit is [Nm] where 1Nm = 100Ncm = 1000mNm. The BEMF voltage is valid as RMS voltage per coil, thus the nominal current has a factor of 2 in this formula. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 8 42 Selecting Sense Resistors Set the desired maximum motor current by selecting an appropriate value for the sense resistor. The following table shows the RMS current values which can be reached using standard resistors and motor types fitting without additional motor current scaling. Additional 15mΩ PCB resistance are included in the calculation. CHOICE OF RSENSE AND RESULTING MAX. MOTOR CURRENT RSENSE [Ω] RMS current [A] IRUN=31 1.50 1.20 1.00 0.82 0.75 0.68 0.50 470m 390m 330m 270m 220m 180m 150m 0.15 0.18 0.22 0.27 0.29 0.32 0.42 0.45 0.53 0.61 0.73 0.87 1.02 1.18 Fitting motor type at max. current setting (examples) 150mA motor 200mA motor 300mA motor 400mA motor 500mA 600mA 700mA 800mA motor motor motor motor 1A motor *) 1.2A motor *) *) At high currents, duty cycle restriction for motion might apply, due to heat up of IC and board. Sense resistors should be carefully selected. The full motor current flows through the sense resistors. Due to chopper operation the sense resistors see pulsed current from the MOSFET bridges. Therefore, a low-inductance type such as film or composition resistors is required to prevent voltage spikes causing ringing on the sense voltage inputs leading to unstable measurement results. Also, a lowinductance, low-resistance PCB layout is essential. Any common GND path for the two sense resistors must be avoided, because this would lead to coupling between the two current sense signals. A massive ground plane is best. Please also refer to layout considerations in chapter 20. The sense resistor needs to be able to conduct the peak motor coil current in motor standstill conditions, unless standby power is reduced. Under normal conditions, the sense resistor conducts less than the coil RMS current, because no current flows through the sense resistor during the slow decay phases. A 0.25W type is sufficient for most applications up to 800mA RMS. Attention Be sure to use a symmetrical sense resistor layout and short and straight sense resistor traces of identical length. Well matching sense resistors ensure best performance. A compact layout with massive ground plane is best to avoid parasitic resistance effects. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 9 43 Motor Current Control The basic motor current is set by the value of the sense resistors. Several possibilities allow scaling down motor current, e.g. to adapt for different motors, or to reduce motor current in standstill or low load situations. METHODS FOR SCALING MOTOR CURRENT Method Pin EN Pin PDN_UART UART interface Parameters Disable / enable driver stage Disable / enable standstill current reduction to IHOLD IHOLD_IRUN TPOWERDOWN Range 1: Motor enable 0: Motor disable 0: Standstill current reduction enabled. 1: Disable IRUN, IHOLD: 1/32 to 32/32 of full scale current. Primary Use - Disable motor to allow freewheeling or power saving - Enable current reduction to reduce heat up in stand still - Fine programming of run and hold (stand still) current Change IRUN for situation specific motor current (range 8 to 31) Select the sense resistor to deliver enough current for the motor at full current scale. This is the default current scaling (IRUN = 31). STANDALONE MODE RMS RUN CURRENT CALCULATION: 𝐼𝑅𝑀𝑆 = 325𝑚𝑉 1 ∗ 𝑅𝑆𝐸𝑁𝑆𝐸 + 30𝑚Ω √2 IRUN and IHOLD allow for scaling of the actual current scale (CS) from 9/32 (IRUN, minimum value), resp. 1/32 to 32/32 when using UART interface, or via automatic standstill current reduction: RMS CURRENT CALCULATION WITH UART CONTROL OPTIONS OR HOLD CURRENT SETTING: 𝐼𝑅𝑀𝑆 = 𝐶𝑆 + 1 𝑉𝐹𝑆 1 ∗ ∗ 32 𝑅𝑆𝐸𝑁𝑆𝐸 + 30𝑚Ω √2 CS is the current scale setting as set by the IHOLD and IRUN. VFS is the full-scale voltage (please refer to electrical characteristics, VSRT). Default is 325mV. Hint For best precision of current setting, measure and fine tune the current in the application. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 44 PARAMETERS FOR MOTOR CURRENT CONTROL Parameter IRUN IHOLD IHOLD DELAY TPOWER DOWN Description Setting Current scale when motor is running. Scales coil 8 … 31 current values as taken from the internal sine wave table. For proper operation, do not set values lower than 8. Optimum range is 16 to 32. Identical to IRUN, but for motor in stand still. 0 … 31 Allows smooth current reduction from run current 0 to hold current. IHOLDDELAY controls the number 1 … 15 of clock cycles for motor power down after TPOWERDOWN in increments of 2^18 clocks: 0=instant power down, 1..15: Current reduction delay per current step in multiple of 2^18 clocks. Example: When using IRUN=31 and IHOLD=16, 15 current steps are required for hold current reduction. A IHOLDDELAY setting of 4 thus results in a power down time of 4*15*2^18 clock cycles, i.e. roughly one second at 16MHz clock frequency. Sets the delay time from stand still (stst) detection 0 … 255 to motor current power down. Time range is about 0 to 5.6 seconds. www.trinamic.com Comment scaling factor 0: 1/32, …, 8: 9/32 … 31: 32/32 IRUN is full scale (setting 31) in standalone mode. instant IHOLD 1*218 … 15*218 clocks per current decrement 0…((2^8)-1) * 2^18 tCLK A minimum setting of 2 is required to allow automatic tuning of PWM_OFFS_AUTO TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 45 10 StallGuard4 Load Measurement UART StallGuard4 provides an accurate measurement of the load on the motor. It is developed for operation in conjunction with StealthChop. StallGuard can be used for stall detection as well as other uses at loads below those which stall the motor, such as CoolStep load-adaptive current reduction. The StallGuard4 measurement value changes linearly over a wide range of load, velocity, and current settings, as shown in Figure 10.1. When approaching maximum motor load, the value goes down to a motor-specific lower value. This corresponds to a load angle of 90° between the magnetic field of the coils and magnets in the rotor. This also is the most energy-efficient point of operation for the motor. 500 StallGuard4 reading SG_RESULT 450 Start value depends on motor, velocity and operating current 400 350 SG_RESULT reaches compare value and indicates danger of stall. This point is set by stallGuard threshold value SGTHRS. 300 100% load value depends on motor, operating current and velocity 250 200 Stall detection 150 threshold SGTHRS*2 high 100 Stall Output low 50 0 Motor stalls above this point. Load angle exceeds 90° and available torque sinks. 10 20 30 40 50 60 70 80 90 100 motor load (% max. torque) Figure 10.1 Function principle of StallGuard4 Parameter SGTHRS Status word SG_RESULT Description This value controls the StallGuard4 threshold level for stall detection. It compensates for motor specific characteristics and controls sensitivity. A higher value gives a higher sensitivity. A higher value makes StallGuard4 more sensitive and requires less torque to indicate a stall. Description This is the StallGuard4 result. A higher reading indicates less mechanical load. A lower reading indicates a higher load and thus a higher load angle. Setting 0… 255 Comment The double of this value is compared to SG_RESULT. The stall output becomes active if SG_RESULT fall below this value. Range 0… 510 Comment Low value: highest load High value: high load In order to use StallGuard4, check the sensitivity of the motor at border conditions. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 46 10.1 Tuning StallGuard4 The StallGuard4 value SG_RESULT is affected by motor-specific characteristics and application-specific demands on load, coil current, and velocity. Therefore, the easiest way to tune the StallGuard4 threshold SGTHRS for a specific motor type and operating conditions is interactive tuning in the actual application. INITIAL PROCEDURE FOR TUNING STALLGUARD SGTHRS 1. 2. 3. 4. Operate the motor at the normal operation velocity for your application and monitor SG_RESULT. Apply slowly increasing mechanical load to the motor. Check the lowest value of SG_RESULT before the motor stalls. Use this value as starting value for SGTHRS (apply half of the value). Now monitor the StallGuard output signal via DIAG output (configure properly, also set TCOOLTHRS) and stop the motor when a pulse is seen on the respective output. Make sure, that the motor is safely stopped whenever it is stalled. Increase SGTHRS if the motor becomes stopped before a stall occurs. The optimum setting is reached when a stall is safely detected and leads to a pulse at DIAG in the moment where the stall occurs. SGTHRS in most cases can be tuned for a certain motion velocity or a velocity range. Make sure, that the setting works reliable in a certain range (e.g. 75% to 150% of desired velocity) and also under extreme motor conditions (lowest and highest applicable temperature). DIAG is pulsed by StallGuard, when SG_RESULT falls below SGTHRS. It is only enabled in StealthChop mode, and when TCOOLTHRS ≥ TSTEP The external motion controller should react to a single pulse by stopping the motor if desired. Set TCOOLTHRS to match the lower velocity threshold where StallGuard delivers a good result. SG_RESULT measurement has a high resolution, and there are a few ways to enhance its accuracy, as described in the following sections. 10.2 StallGuard4 Update Rate The StallGuard4 measurement value SG_RESULT is updated with each full step of the motor. This is enough to safely detect a stall, because a stall always means the loss of four full steps. 10.3 Detecting a Motor Stall To safely detect a motor stall, the stall threshold must be determined using a specific SGTHRS setting and a specific motor velocity or velocity range. Further, the motor current setting has a certain influence and should not be modified, once optimum values are determined. Therefore, the maximum load needs to be determined that the motor can drive without stalling. At the same time, monitor SG_RESULT at this load. The stall threshold should be a value safely within the operating limits, to allow for parameter stray. More refined evaluation may also react to a change of SG_RESULT rather than comparing to a fixed threshold. This will rule out certain effects which influence the absolute value. 10.4 Limits of StallGuard4 Operation StallGuard4 does not operate reliably at extreme motor velocities: Very low motor velocities (for many motors, less than one revolution per second) generate a low back EMF and make the measurement unstable and dependent on environment conditions (temperature, etc.). Other conditions will also lead to a poor response of the measurement value SG_RESULT to the motor load. Very high motor velocities, in which the full sinusoidal current is not driven into the motor coils also leads to poor response. These velocities are typically characterized by the motor back EMF exceeding the supply voltage. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 47 11 CoolStep Operation UART CoolStep is an automatic smart energy optimization for stepper motors based on the motor mechanical load, making them “green”. 11.1 User Benefits Energy efficiency Motor generates less heat Less cooling infrastructure Cheaper motor – – – – consumption decreased up to 90% improved mechanical precision for motor and driver does the job! CoolStep allows substantial energy savings, especially for motors which see varying loads or operate at a high duty cycle. Because a stepper motor application needs to work with a torque reserve of 30% to 50%, even a constant-load application allows significant energy savings because CoolStep automatically enables torque reserve when required. Reducing power consumption keeps the system cooler, increases motor life, and allows reducing cost in the power supply and cooling components. Reducing motor current by half results in reducing power by a factor of four. 11.2 Setting up for CoolStep CoolStep is controlled by several parameters, but two are critical for understanding how it works: Parameter Description SEMIN 4-bit unsigned integer that sets a lower threshold. 0 If SG_RESULT goes below this threshold, CoolStep 1…15 increases the current to both coils. The 4-bit SEMIN value is scaled by 32 to cover the lower half of the range of the 10-bit SG value. (The name of this parameter is derived from SmartEnergy, which is an earlier name for CoolStep.) 4-bit unsigned integer that controls an upper 0…15 threshold. If SG is sampled equal to or above this threshold enough times, CoolStep decreases the current to both coils. The upper threshold is (SEMIN + SEMAX + 1)*32. SEMAX Figure - Range Comment disable CoolStep threshold is SEMIN*32 Once SGTHRS has been determined, use 1/16*SGTHRS+1 as a starting point for SEMIN. threshold is (SEMIN+SEMAX+1)*32 0 to 2 recommended 11.1 shows the operating regions of CoolStep: The black line represents the SG_RESULT measurement value. The blue line represents the mechanical load applied to the motor. The red line represents the current into the motor coils. When the load increases, SG_RESULT falls below SEMIN, and CoolStep increases the current. When the load decreases, SG_RESULT rises above (SEMIN + SEMAX + 1) * 32, and the current is reduced. www.trinamic.com stallGuard2 reading mechanical load 48 motor current TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) current setting I_RUN (upper limit) motor current reduction area SEMAX+SEMIN+1 SEMIN ½ or ¼ I_RUN (lower limit) motor current increment area 0=maximum load load angle optimized Zeit slow current reduction due to reduced motor load load angle optimized current increment due to increased load stall possible load angle optimized Figure 11.1 CoolStep adapts motor current to the load Five more parameters control CoolStep and one status value is returned: Parameter SEUP SEDN SEIMIN TCOOLTHRS Status word CSACTUAL Description Range Sets the current increment step. The current 0…3 becomes incremented for each measured StallGuard2 value below the lower threshold. Sets the number of StallGuard2 readings above 0…3 the upper threshold necessary for each current decrement of the motor current. Sets the lower motor current limit for CoolStep operation by scaling the IRUN current setting. Operate well above the minimum motor current as determined for StealthChop current regulation. Lower velocity threshold for switching on CoolStep and stall output. Below this velocity CoolStep becomes disabled (not used in STEP/DIR mode). Adapt to the lower limit of the velocity range where StallGuard2 gives a stable result. Description 0 1 number of StallGuard2 measurements per decrement: 32, 8, 2, 1 0: 1/2 of IRUN 1: 1/4 of IRUN IRUN ≥ 16 recommended 1… 2^20-1 Specifies lower CoolStep velocity by comparing the threshold value to TSTEP Range Comment This status value provides the actual motor 0…31 current scale as controlled by CoolStep. The value goes up to the IRUN value and down to the portion of IRUN as specified by SEIMIN. www.trinamic.com Comment step width is 1, 2, 4, 8 1/32, 2/32, … 32/32 TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 49 11.3 Tuning CoolStep CoolStep uses SG_RESULT to operate the motor near the optimum load angle of +90°. The basic setting to be tuned is SEMIN. Set SEMIN to a value which safely activates CoolStep current increment before the motor stalls. In case SGTHRS has been tuned before, a lower starting value is SEMIN = 1+SGTHRS/16. The current increment speed is specified in SEUP, and the current decrement speed is specified in SEDN. They can be tuned separately because they are triggered by different events that may need different responses. The encodings for these parameters allow the coil currents to be increased much more quickly than decreased, because crossing the lower threshold is a more serious event that may require a faster response. If the response is too slow, the motor may stall. In contrast, a slow response to crossing the upper threshold does not risk anything more serious than missing an opportunity to save power. CoolStep operates between limits controlled by the current scale parameter IRUN and the seimin bit. Attention When CoolStep increases motor current, spurious detection of motor stall may occur. For best results, disable CoolStep during StallGuard based homing. In case StallGuard is desired in combination with CoolStep, try increasing coolStep lower threshold SEMIN as required. 11.3.1 Response Time For fast response to increasing motor load, use a high current increment step SEUP. If the motor load changes slowly, a lower current increment step can be used to avoid motor oscillations. Hint The most common and most beneficial use is to adapt CoolStep for operation at the typical system target operation velocity and to set the velocity thresholds according. As acceleration and decelerations normally shall be quick, they will require the full motor current, while they have only a small contribution to overall power consumption due to their short duration. 11.3.2 Low Velocity and Standby Operation Because CoolStep is not able to measure the motor load in standstill and at very low RPM, a lower velocity threshold is provided for enabling CoolStep. It should be set to an application specific default value. Below this threshold the normal current setting via IRUN respectively IHOLD is valid. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 50 12 STEP/DIR Interface The STEP and DIR inputs provide a simple, standard interface compatible with many existing motion controllers. The microPlyer step pulse interpolator brings the smooth motor operation of highresolution microstepping to applications originally designed for coarser stepping. 12.1 Timing Figure 12.1 shows the timing parameters for the STEP and DIR signals, and the table below gives their specifications. Only rising edges are active. STEP and DIR are sampled and synchronized to the system clock. If the signal source is far from the chip, and especially if the signals are carried on cables, the signals should be filtered or differentially transmitted. +VCC_IO DIR SchmittTrigger tSH tDSU tSL tDSH STEP or DIR Input STEP 0.56 VCC_IO Internal Signal 0.44 VCC_IO Active edge (DEDGE=0) Active edge (DEDGE=0) Figure 12.1 STEP and DIR timing, Input pin filter STEP and DIR interface timing Parameter step frequency (at maximum microstep resolution) fullstep frequency STEP input minimum low time STEP input minimum high time DIR to STEP setup time DIR after STEP hold time www.trinamic.com AC-Characteristics (taking into account possible lowest internal clock generator frequency) Symbol fSTEP fFS tSL tSH tDSU tDSH Conditions Min 120 120 20 20 Typ Max 4 Unit MHz 8 kHz ns ns ns ns TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 51 12.2 Changing Resolution The TMC2300 includes an internal microstep table with 1024 sine wave entries to generate sinusoidal motor coil currents. These 1024 entries correspond to one electrical revolution or four fullsteps. The microstep resolution setting determines the step width taken within the table. Depending on the DIR input, the microstep counter is increased (DIR=0) or decreased (DIR=1) with each STEP pulse by the step width. The microstep resolution determines the increment respectively the decrement. At maximum resolution, the sequencer advances one step for each step pulse. At half resolution, it advances two steps. Increment is up to 256 steps for fullstepping. The sequencer has special provision to allow seamless switching between different microstep rates at any time. When switching to a lower microstep resolution, it calculates the nearest step within the target resolution and reads the current vector at that position. This behavior especially is important for low resolutions like fullstep and halfstep, because any failure in the step sequence would lead to asymmetrical run when comparing a motor running clockwise and counterclockwise. EXAMPLES: Fullstep: Cycles through table positions: 128, 384, 640 and 896 (45°, 135°, 225° and 315° electrical position, both coils on at identical current). The coil current in each position corresponds to the RMS-Value (0.71 * amplitude). Step size is 256 (90° electrical) Half step: The first table position is 64 (22.5° electrical), Step size is 128 (45° steps) Quarter step: The first table position is 32 (90°/8=11.25° electrical), Step size is 64 (22.5° steps) This way equidistant steps result and they are identical in both rotation directions. Some older drivers also use zero current (table entry 0, 0°) as well as full current (90°) within the step tables. This kind of stepping is avoided because it provides less torque and has a worse power dissipation in driver and motor. Step position Half step 0 Full step 0 Half step 1 Half step 2 Full step 1 Half step 3 Half step 4 Full step 2 Half step 5 Half step 6 Full step 3 Half step 7 table position 64 128 192 320 384 448 576 640 704 832 896 960 current coil A 38.3% 70.7% 92.4% 92.4% 70.7% 38.3% -38.3% -70.7% -92.4% -92.4% -70.7% -38.3% current coil B 92.4% 70.7% 38.3% -38.3% -70.7% -92.4% -92.4% -70.7% -38.3% 38.3% 70.7% 92.4% See chapter 3.2.1 for resolution settings available in stand-alone mode. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 52 12.3 MicroPlyer Step Interpolator and Stand Still Detection For each active edge on STEP, MicroPlyer produces microsteps at 256x resolution, as shown in Figure 12.2. It interpolates the time in between of two step impulses at the step input based on the last step interval. This way, from 2 microsteps (128 microstep to 256 microstep interpolation) up to 256 microsteps (full step input to 256 microsteps) are driven for a single step pulse. The step rate for the interpolated 2 to 256 microsteps is determined by measuring the time interval of the previous step period and dividing it into up to 256 equal parts. The maximum time between two microsteps corresponds to 220 (roughly one million system clock cycles), for an even distribution of 256 microsteps. At 12 MHz system clock frequency, this results in a minimum step input frequency of roughly 12 Hz for MicroPlyer operation. A lower step rate causes a standstill event to be detected. At that frequency, microsteps occur at a rate of (system clock frequency)/216 ~ 256 Hz. When a stand still is detected, the driver automatically begins standby current reduction if selected by pin PDN. Active edge (dedge=0) Active edge (dedge=0) Active edge (dedge=0) Active edge (dedge=0) Attention MicroPlyer only works perfectly with a jitter-free STEP frequency. STEP Interpolated microstep 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 Motor angle 2^20 tCLK STANDSTILL (stst) active Figure 12.2 microPlyer microstep interpolation with rising STEP frequency (Example: 16 to 256) In Figure 12.2, the first STEP cycle is long enough to set the stst bit standstill. Detection of standstill will enable the standby current reduction. This bit is cleared on the next STEP active edge. Then, the external STEP frequency increases. After one cycle at the higher rate microPlyer adapts the interpolated microstep rate to the higher frequency. During the last cycle at the slower rate, microPlyer did not generate all 16 microsteps, so there is a small jump in motor angle between the first and second cycles at the higher rate. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 53 12.4 Index Signal An active index output (enable diag_index) signals that the sine curve of motor coil A is at its positive zero transition. This correlates to the zero point of the microstep sequence. Usually, the cosine curve of coil B is at its maximum at the same time. Thus, the index signal is active once within each electrical period, and corresponds to a defined position of the motor within a sequence of four fullsteps. The index output this way allows the detection of a certain microstep pattern, and thus helps to detect a position with more precision than a stop switch can do. Current COIL A 0 COIL B Time INDEX Current Time STEPS Time Figure 12.3 Index signal at positive zero transition of the coil A sine curve Hint The index output allows precise detection of the microstep position within one electrical wave, i.e. within a range of four fullsteps. With this, homing accuracy and reproducibility can be enhanced to microstep accuracy, even when using an inexpensive home switch. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 54 13 Internal Step Pulse Generator UART The TMC2300 integrates a high-resolution step pulse generator, allowing motor motion via the UART interface. However, no velocity ramping is provided. Ramping is not required, if the target motion velocity is smaller than the start & stop frequency of the motor. For higher velocities, ramp up the frequency in small steps to accelerate the motor, and ramp down again to decelerate the motor. Figure 13.1 shows an example motion profile ramping up the motion velocity in discrete steps. Choose the ramp velocity steps considerably smaller than the maximum start velocity of the motor, because motor torque drops at higher velocity, and motor load at higher velocity typically increases. motor stop v acceleration constant velocity deceleration Th eo re t ica l pr of ile Target Velocity Stop velocity Start velocity 0 t VACTUAL Figure 13.1 Software generated motion profile PARAMETER VS. UNITS Parameter / Symbol fCLK[Hz] Unit [Hz] µstep velocity v[Hz] µsteps / s USC microstep count counts rotations per second v[rps] rotations / s TSTEP, TCOOLTHRS - VACTUAL Two’s complement signed internal velocity calculation / description / comment clock frequency of the TMC2300 in [Hz] v[Hz] = VACTUAL[2300] * ( fCLK[Hz] / 2^24 ) With nominal oscillator: v[Hz] = VACTUAL[2300] * 0.715Hz microstep resolution in number of microsteps (i.e. the number of microsteps between two fullsteps – normally 256) v[rps] = v[Hz] / USC / FSC FSC: motor fullsteps per rotation, e.g. 200 TSTEP = fCLK / fSTEP The time reference for velocity threshold is referred to the actual microstep frequency of the step input respectively velocity v[Hz]. VACTUAL[2300] = ( fCLK[Hz]/2 / 2^23 ) / v[Hz] With nominal oscillator: VACTUAL[2300] = 0.715Hz / v[Hz] Hint To monitor internal step pulse execution, program the DIAG output to provide step pulses (GCONF.diag_step). It toggles upon each step and thus shows half the microstep frequency. Use a timer input on your CPU to count pulses. Alternatively, regularly poll MSCNT to grasp steps done in the previous polling interval. It wraps around from 1023 to 0. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 55 14 Driver Diagnostic Flags The TMC2300 drivers supply a complete set of diagnostic and protection capabilities, like short to GND protection, short to VS protection and undervoltage detection. A detection of an open load condition allows testing if a motor coil connection is interrupted. See the DRV_STATUS table for details. 14.1 Temperature Measurement The driver integrates a two-level temperature sensor (pre-warning and thermal shutdown) for diagnostics and for protection of the IC against excess heat. Heat is mainly generated by the motor driver stages. Most critical situations, where the driver MOSFETs could be overheated, are avoided by the short to GND protection. For many applications, the overtemperature pre-warning will indicate an abnormal operation situation and can be used to initiate user warning or power reduction measures like motor current reduction. The thermal shutdown is just an emergency measure and temperature rising to the shutdown level should be prevented by design. TEMPERATURE THRESHOLDS Temperature Level 150°C 120°C Comment This value is relatively safe to switch off the driver stage before the IC can be destroyed by overheating. On a large PCB, the power MOSFETs reach roughly 150°C peak temperature when the temperature detector is triggered with this setting. Temperature level for pre-warning. In most applications, reaching this level is a sign for abnormal heat accumulation. The overtemperature pre-warning threshold of 120°C gives lots of headroom to react to high driver temperature, e.g. by reducing motor current, or increasing waiting-time in between of two motions. Attention Overtemperature protection cannot in all cases avoid thermal destruction motor current is exceed, e.g. by operating a motor in StealthChop with automatic tuning parameters not fitting the operating conditions, excess heat up the driver before the overtemperature sensor can react. This conduction over the IC die. of the IC. In case the rated wrong parameters, or with heat generation can quickly is due to a delay in heat After triggering the overtemperature sensor (ot flag), the driver remains switched off until the system temperature falls below the pre-warning level (otpw) to avoid continuous heating to the shutdown level. 14.2 Short Protection The TMC2300 power stages are protected against a short circuit condition by an additional measurement of the current flowing through each of the power stage MOSFETs. This is important, as most short circuit conditions result from a motor cable insulation defect, e.g. when touching the conducting parts connected to the system ground. The short detection is protected against spurious triggering, e.g. by ESD discharges, by retrying three times before switching off the motor. Once a short condition is safely detected, the both driver bridges become switched off, and the s2ga or s2gb flag, respectively s2vsa or s2vsb becomes set. In order to restart the motor, disable and reenable the driver. Note, that short protection cannot protect the system and the power stages for all possible short events, as a short event is rather undefined and a complex network of external components may be involved. Therefore, short circuits should basically be avoided. www.trinamic.com TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 56 14.3 Open Load Diagnostics UART Interrupted cables are a common cause for systems failing, e.g. when connectors are not firmly plugged. The TMC2300 detects open load conditions by checking, if it can reach the desired motor coil current. This way, also undervoltage conditions, high motor velocity settings or short and overtemperature conditions may cause triggering of the open load flag, and inform the user, that motor torque may suffer. In motor stand still, open load cannot always be measured, as the coils might eventually have zero current. Open load detection is provided for system debugging. In order to safely detect an interrupted coil connection, read out the open load flags at low or nominal motor velocity operation, only. A flicker may occur with asymmetric sense resistors and does not harm. However, the ola and olb flags have just informative character and do not cause any action of the driver. 14.4 Diagnostic Output drv_err The diagnostic output DIAG provides important status information. An active DIAG output shows that the driver cannot work normally. The index output signals the microstep counter zero position, to allow referencing (homing) a drive to a certain current pattern. The function set of the DIAG output can be modified by UART. Figure 14.1 shows the available signals and control bits. Q S R Short circuit (s2vs, s2g) over temperature (ot) Power stage disable (e.g. pin EN, STANDBY) DIAG MUX Power-on reset Overtemperature (ot) StallDetection (gated by TSTEP