TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 1 TMC 246/A – DATA SHEET High Current Microstep Stepper Motor Driver with sensorless stall detection, protection / diagnosis and SPI Interface TRINAMIC® Motion Control GmbH & Co KG Sternstraße 67 D – 20357 Hamburg GERMANY T +49 - (0) 40 - 51 48 06 - 0 F +49 - (0) 40 - 51 48 06 - 60 WWW.TRINAMIC.COM [email protected] Features The TMC246 / TMC246A (1) is a dual full bridge driver IC for bipolar stepper motor control applications. The integrated unique sensorless stall detection (pat. pend.) StallGuard™ makes it a good choice for applications, where a reference point is needed, but where a switch is not desired. Its ability to predict an overload makes the TMC246 an optimum choice for drives, where a high reliability is desired. The TMC246 is realized in a HVCMOS technology combined with Low-RDS-ON high efficiency MOSFETs (pat. pend.). It allows to drive a coil current of up to 1500mA even at high environment temperatures. Its low current consumption and high efficiency together with the miniature package make it a perfect solution for embedded motion control and for battery powered devices. Internal DACs allow microstepping as well as smart current control. The device can be controlled by a serial interface (SPI™i) or by analog / digital input signals. Short circuit, temperature, undervoltage and overvoltage protection are integrated. • • • • • • • • • • • • • • Sensorless stall detection StallGuard™ and load measurement integrated Control via SPI with easy-to-use 12 bit protocol or external analog / digital signals Short circuit, overvoltage and overtemperature protection integrated Status flags for overcurrent, open load, over temperature, temperature pre-warning, undervoltage Integrated 4 bit DACs allow up to 16 times microstepping via SPI, any resolution via analog control Mixed decay feature for smooth motor operation Slope control user programmable to reduce electromagnetic emissions Chopper frequency programmable via a single capacitor or external clock Current control allows cool motor and driver operation 7V to 34V motor supply voltage (A-type) Up to 1500mA output current and more than 800mA at 105°C 3.3V or 5V operation for digital part Low power dissipation via low RDS-ON power stage Standby and shutdown mode available (1) The term TMC246 in this datasheet always refers to the TMC246A and the TMC246. The major differences in the older TMC246 are explicitly marked with “non-A-type”. The TMC246A brings a number of enhancements and is fully backward compatible to the TMC246. Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 2 FEATURES ............................................................................................................................................1 PINNING.................................................................................................................................................5 PACKAGE CODES ...................................................................................................................................5 PQFP44 DIMENSIONS ..........................................................................................................................6 APPLICATION CIRCUIT / BLOCK DIAGRAM .....................................................................................7 PIN FUNCTIONS .....................................................................................................................................7 LAYOUT CONSIDERATIONS ...............................................................................................................8 CONTROL VIA THE SPI INTERFACE ..................................................................................................9 SERIAL DATA WORD TRANSMITTED TO TMC246 ......................................................................................9 SERIAL DATA WORD TRANSMITTED FROM TMC246..................................................................................9 TYPICAL WINDING CURRENT VALUES .....................................................................................................10 BASE CURRENT CONTROL VIA INA AND INB IN SPI MODE ......................................................................10 CONTROLLING THE POWER DOWN MODE VIA THE SPI INTERFACE ...........................................................10 OPEN LOAD DETECTION .......................................................................................................................11 STANDBY AND SHUTDOWN MODE ..........................................................................................................11 POWER SAVING ...................................................................................................................................11 STALL DETECTION ............................................................................................................................12 USING THE SENSORLESS LOAD MEASUREMENT .....................................................................................12 IMPLEMENTING SENSORLESS STALL DETECTION ....................................................................................12 PROTECTION FUNCTIONS................................................................................................................13 OVERCURRENT PROTECTION AND DIAGNOSIS ........................................................................................13 OVERTEMPERATURE PROTECTION AND DIAGNOSIS ................................................................................13 OVERVOLTAGE PROTECTION AND ENN PIN BEHAVIOR ...........................................................................13 CHOPPER PRINCIPLE........................................................................................................................14 CHOPPER CYCLE / USING THE MIXED DECAY FEATURE ...........................................................................14 BLANK TIME ........................................................................................................................................14 BLANK TIME SETTINGS .........................................................................................................................14 CLASSICAL NON-SPI CONTROL MODE (STAND ALONE MODE) ................................................15 PIN FUNCTIONS IN STAND ALONE MODE .................................................................................................15 INPUT SIGNALS FOR MICROSTEP CONTROL IN STAND ALONE MODE ..........................................................15 CALCULATION OF THE EXTERNAL COMPONENTS......................................................................16 SENSE RESISTOR ................................................................................................................................16 EXAMPLES FOR SENSE RESISTOR SETTINGS ..........................................................................................16 HIGH SIDE OVERCURRENT DETECTION RESISTOR RSH ............................................................................16 MAKING THE CIRCUIT SHORT CIRCUIT PROOF.........................................................................................17 OSCILLATOR CAPACITOR .....................................................................................................................18 TABLE OF OSCILLATOR FREQUENCIES ...................................................................................................18 PULLUP RESISTORS ON UNUSED INPUTS ...............................................................................................18 SLOPE CONTROL RESISTOR ................................................................................................................19 EXAMPLE FOR SLOPE SETTINGS ...........................................................................................................19 ABSOLUTE MAXIMUM RATINGS......................................................................................................20 ELECTRICAL CHARACTERISTICS ...................................................................................................20 OPERATIONAL RANGE .........................................................................................................................20 DC CHARACTERISTICS ........................................................................................................................21 AC CHARACTERISTICS ........................................................................................................................22 THERMAL PROTECTION ........................................................................................................................22 THERMAL CHARACTERISTICS ...............................................................................................................23 TYPICAL POWER DISSIPATION AT HIGH LOAD / HIGH TEMPERATURE ........................................................23 Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 3 SPI INTERFACE TIMING.....................................................................................................................24 PROPAGATION TIMES ..........................................................................................................................24 USING THE SPI INTERFACE ..................................................................................................................24 SPI FILTER .........................................................................................................................................24 ESD PROTECTION..............................................................................................................................25 APPLICATION NOTE: EXTENDING THE MICROSTEP RESOLUTION ...........................................26 Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) Life support policy TRINAMIC Motion Control GmbH & Co KG does not authorize or warrant any of its products for use in life support systems, without the specific written consent of TRINAMIC Motion Control GmbH & Co KG. Life support systems are equipment intended to support or sustain life, and whose failure to perform, when properly used in accordance with instructions provided, can be reasonably expected to result in personal injury or death. © TRINAMIC Motion Control GmbH & Co KG 2005 Information given in this data sheet is believed to be accurate and reliable. However no responsibility is assumed for the consequences of its use nor for any infringement of patents or other rights of third parties, which may result form its use. Specifications subject to change without notice. Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG 4 TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 5 ANN AGND SLP INA INB VCC GND - - VS VT - 44 43 42 41 40 39 38 37 36 35 34 Pinning 1 33 2 32 3 31 4 30 5 29 OA1 VSA OB1 TMC 246 / 236A QFP44 OA2 6 7 VSB OB2 28 27 OA1 BRA BL2 OB1 8 26 9 25 10 24 11 23 13 14 15 16 17 18 19 20 21 22 SDO SDI SCK GND CSN ENN SPE BL1 SRB SRA 12 OB2 OSC OA2 BRB Package codes Type TMC246A TMC246 Package PQFP44 PQFP44 Temperature range automotive (1) automotive (1) Lead free (ROHS) Yes From date code 30/04 Code/marking TMC246A-PA TMC246-PA (1) ICs are not tested according to automotive standards, but are usable within the complete automotive temperature range. Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 6 E F G PQFP44 Dimensions I D C REF A C D E F G H I K L MIN. MAX. 12 10 1 0.09 0.05 0.30 0.45 1.6 0.2 0.15 0.45 0.75 0.8 0 0.08 A All dimensions are in mm. L: Co-planarity of pins H K Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 7 Application Circuit / Block Diagram +VM BL1 BL2 220nF VS TMC246 OSC 100µF RSH VT VSA OSC Current Controlled Gate Drivers Undervoltage VCC PWM-CTRL +VCC 1nF 100nF Temperature P P OA1 Coil A OA2 N N BRA SDI [PHB] SDO Parallel Control [ERR] CSN SRA 0 Load mesurement [PHA] Control & Diagnosis SCK SPIInterface RS [MDBN] DAC 4 1 INA REFSEL VREF DAC INB 4 1 SRB 0 RS PWM-CTRL Current Controlled Gate Drivers BRB ENN VCC/2 REFSEL N N OB1 OB2 P Coil B P VSB SPE ANN AGND GND SLP [MDAN] stand alone mode RSLP [...]: function in stand alone mode Pin Functions Pin Function Pin Function VS Motor supply voltage VT Short to GND detection comparator – connect to VS if not used VCC 3.0-5.5V supply voltage for analog GND and logic circuits Digital / Power ground AGND Analog ground (Reference for SRA, OSC SRB, OSC, SLP, INA, INB, SLP) Oscillator capacitor or external clock input for chopper INA Analog current control phase A INB Analog current control input phase B SCK Clock input of serial interface SDO Data output of serial interface (tristate) SDI Data input of serial interface CSN Chip select input of serial interface ENN Device enable (low active), and SPE overvoltage shutdown input Enable SPI mode (high active). Tie to GND for non-SPI applications ANN Enable analog current control via SLP INA and INB (low active) Slope control resistor. BL1, BL2 Digital blank time select SRA, SRB Bridge A/B current sense resistor input OA1, OA2 Output of full-bridge A OB1, OB2 Output of full-bridge B VSA, VSB Supply voltage for bridge A/B BRA, BRB Bridge A/B sense resistor Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 8 Layout Considerations For optimal operation of the circuit a careful board layout is important, because of the combination of high current chopper operation coupled with high accuracy threshold comparators. Please pay special attention to a massive grounding. Depending on the required motor current, either a single massive ground plane or a ground plane plus star connection of the power traces may be used. The schematic shows how the high current paths can be routed separately, so that the chopper current does not flow through the system’s GND-plane. Tie the TMC246’s AGND and GND to the GND plane. Additionally, use enough filtering capacitors located near to the board’s power supply input and small ceramic capacitors near to the power supply connections of the TMC246. Use low inductance sense resistors, or add a ceramic capacitor in parallel to each resistor to avoid high voltage spikes. In some applications it may become necessary to introduce additional RC-filtering into the VT and SRA / SRB line, as shown in the schematic, to prevent spikes from triggering the short circuit protection or the chopper comparator. Be sure to connect all pins of the PQFP package for each of the double/quad output pins externally. Each two of these output pins should be treated as if they were fused to a single wide pin (as shown in the drawing). Each two pins are used as cooling fin for one of the eight integrated output power transistors. Use massive motor current traces on all these pins and multiple vias, if the output trace is changed to a different layer near the package. A symmetrical layout on all of the OA and OB pins is required, to ensure proper heat dissipation on all output transistors. Otherwise proper function of the thermal protection can not be guaranteed! A multi-layer PCB shows superior thermal performance, because it allows usage of a massive GND plane, which will act as a heat spreader. The heat will be coupled vertically from the output traces to the GND plane, since vertical heat distribution in PCBs is quite effective. Heat dissipation can be improved by attaching a heat sink to the package directly. Please be aware, that long or thin traces to the sense resistors may add substantial resistance and thus reduce output current. The same is valid for the high side shunt resistor. Use short and straight traces to avoid parasitic inductivities, because these can generate large voltage spikes and EMV problems. optional voltage divider VS RDIV RSH 100nF VT +VM 100R GND VSA TMC236/ TMC246 VSB BRA CVM BRB SRA optional filter 100R SRB 100R 3.3 10nF RSA RSB GND AGND GNDPlane Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 9 Control via the SPI Interface The SPI data word sets the current and polarity for both coils. By applying consecutive values, describing a sine and a cosine wave, the motor can be driven in microsteps. Every microstep is initiated by its own telegram. Please refer to the description of the analog mode for details on the waveforms required. The SPI interface timing is described in the timing section. We recommend the TMC428 to automatically generate the required telegrams and motor ramps for up to three motors. Serial data word transmitted to TMC246 (MSB transmitted first) Bit Name Function Remark 11 MDA mixed decay enable phase A “1” = mixed decay 10 CA3 current bridge A.3 MSB 9 CA2 current bridge A.2 8 CA1 current bridge A.1 7 CA0 current bridge A.0 LSB 6 PHA polarity bridge A “0” = current flow from OA1 to OA2 5 MDB mixed decay enable phase B “1” = mixed decay 4 CB3 current bridge B.3 MSB 3 CB2 current bridge B.2 2 CB1 current bridge B.1 1 CB0 current bridge B.0 LSB 0 PHB polarity bridge B “0” = current flow from OB1 to OB2 Serial data word transmitted from TMC246 (MSB transmitted first) Bit Name Function Remark 11 LD2 load indicator bit 2 MSB 10 LD1 load indicator bit 1 9 LD0 load indicator bit 0 8 1 always “1” 7 OT overtemperature 6 OTPW temperature prewarning “1” = prewarning temperature exceeded 5 UV driver undervoltage “1” = undervoltage on VS 4 OCHS overcurrent high side 3 PWM cycles with overcurrent within 63 PWM cycles 3 OLB open load bridge B no PWM switch off for 14 oscillator cycles 2 OLA open load bridge A no PWM switch off for 14 oscillator cycles 1 OCB overcurrent bridge B low side 3 PWM cycles with overcurrent within 63 PWM cycles 0 OCA overcurrent bridge A low side 3 PWM cycles with overcurrent within 63 PWM cycles LSB “1” = chip off due to overtemperature Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 10 Typical winding current values Current setting Percentage of CA3..0 / CB3..0 current Typical trip voltage of the current sense comparator (internal reference or analog input voltage of 2V is used) 0000 0% 0V 0001 6.7% 23 mV 0010 13.3% 45 mV ... (bridge continuously in slow decay condition) ... 1110 93.3% 317 mV 1111 100% 340 mV The current values correspond to a standard 4 Bit DAC, where 100%=15/16. The contents of all registers is cleared to “0” on power-on reset or disable via the ENN pin, bringing the chip to a low power standby mode. All SPI inputs have Schmitt-Trigger function. Base current control via INA and INB in SPI mode In SPI mode, the IC can use an external reference voltage for each DAC. This allows the adaptation to different motors. This mode is enabled by tying pin ANN to GND. A 2.0V input voltage gives full scale current of 100%. In this case, the typical trip voltage of the current sense comparator is determined by the input voltage and the DAC current setting (see table above) as follows: VTRIP,A = 0.17 VINA × “percentage SPI current setting A” VTRIP,B = 0.17 VINB × “percentage SPI current setting B” A maximum of 3.0V VIN is possible. Multiply the percentage of base current setting and the DAC table to get the overall coil current. It is advised to operate at a high base current setting, to reduce the effects of noise voltages. This feature allows a high resolution setting of the required motor current using an external DAC or PWM-DAC (see schematic for examples). using PWM signal 8 level via R2R-DAC 2 level control INA µCPort .2 100K R1 51K 47K R2 INB 100nF µCPort .1 10nF 100K 51K AGND +VCC µCPWM µCPort .0 100K µCPort 51K ANN Controlling the power down mode via the SPI interface Bit Standard function Control word function 11 10 9 8 7 6 5 4 3 2 1 0 MxA CA3 CA2 CA1 CA0 PhA MxB CB3 CB2 CB1 CB0 PhB - 0 0 0 0 - - 0 0 0 0 - Enable standby mode and clear error flags Programming current value “0000” for both coils at a time clears the overcurrent flags and switches the TMC246 into a low current standby mode with coils switched off. Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 11 Open load detection Open load is signaled, whenever there are more than 14 oscillator cycles without PWM switch off. Note that open load detection is not possible while coil current is set to “0000”, because the chopper is off in this condition. The open load flag will then always be read as inactive (“0”). During overcurrent and undervoltage or overtemperature conditions, the open load flags also become active! Due to their principle, the open load flags not only signal an open load condition, but also a torque loss of the motor, especially at high motor velocities. To detect only an interruption of the connection to the motor, it is advised to evaluate the flags during stand still or during low velocities only (e.g. for the first or last steps of a movement). Standby and shutdown mode The circuit can be put into a low power standby mode by the user, or, automatically goes to standby on Vcc undervoltage conditions. Before entering standby mode, the TMC246 switches off all power driver outputs. In standby mode the oscillator becomes disabled and the oscillator pin is held at a low state. The standby mode is available via the interface in SPI-mode and via the ENN pin in non-SPI mode. The shutdown mode even reduces supply current further. It can only be entered in SPI-mode by pulling the ENN pin high. In shutdown additionally all internal reference voltages become switched off and the SPI circuit is held in reset. Power saving The possibility to control the output current can dramatically save energy, reduce heat generation and increase precision by reducing thermal stress on the motor and attached mechanical components. Just reduce motor current during stand still: Even a slight reduction of the coil currents to 70% of the current of the last step of the movement, halves power consumption! In typical applications a 50% current reduction during stand still is reasonable. Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 12 Stall Detection Using the sensorless load measurement The TMC246 provides a patented sensorless load measurement, which allows a digital read out of the mechanical load on the motor via the serial interface. To get a readout value, just drive the motor using sine commutation and mixed decay switched off. The load measurement then is available as a three bit load indicator during normal motion of the motor. A higher mechanical load on the motor results in a lower readout value. The value is updated once per fullstep. The load detection is based on the motor’s back EMF, thus the level depends on several factors: - Motor velocity: A higher velocity leads to a higher readout value - Motor resonance: Motor resonances cause a high dynamic load on the motor, and thus measurement may give unsatisfactory results. - Motor acceleration: Acceleration phases also produce dynamic load on the motor. - Mixed decay setting: For load measurement mixed decay has to be off for some time before the zero crossing of the coil current. If mixed decay is used, and the mixed decay period is extended towards the zero crossing, the load indicator value decreases. Implementing sensorless stall detection The sensorless stall detection typically is used, to detect the reference point without the usage of a switch or photo interrupter. Therefore the actuator is driven to a mechanical stop, e.g. one end point in a spindle type actuator. As soon as the stop is hit, the motor stalls. Without stall detection, this would give an audible humming noise and vibrations, which could damage mechanics. To get a reliable stall detection, follow these steps: 1. Choose a motor velocity for reference movement. Use a medium velocity which is far enough away from mechanical resonance frequencies. In some applications even motor start / stop frequency may be used. With this the motor can stop within one fullstep if a stall is detected. 2. Use a sine stepping pattern and switch off mixed decay (at least 1 to 3 microsteps before zero crossing of the wave). Monitor the load indicator during movement. It should show a stable readout value in the range 3 to 7 (LMOVE). If the readout is high (>5), the mixed decay portion may be increased, if desired. 3. Choose a threshold value LSTALL between 0 and LMOVE - 1. 4. Monitor the load indicator during each reference search movement, as soon as the desired velocity is reached. Readout is required at least once per fullstep. If the readout value at one fullstep is below or equal to LSTALL, stop the motor. Attention: Do not read out the value within one chopper period plus 8 microseconds after toggling one of the phase polarities! 5. If the motor stops during normal movement without hitting the mechanical stop, decrease LSTALL. If the stall condition is not detected at once, when the motor stalls, increase LSTALL. v(t) a_ m ax v_max t load indicator acceleration constant velocity max stall LMOVE LSTALL stall threshold min t acceleration jerk stall detected! vibration Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 13 Protection Functions Overcurrent protection and diagnosis The TMC246 uses the current sense resistors on the low side to detect an overcurrent: Whenever a voltage above 0.61V is detected, the PWM cycle is terminated at once and all transistors of the bridge are switched off for the rest of the PWM cycle. The error counter is increased by one. If the error counter reaches 3, the bridge remains switched off for 63 PWM cycles and the error flag is read as “active”. The user can clear the error condition in advance by clearing the error flag. The error counter is cleared, whenever there are more than 63 PWM cycles without overcurrent. There is one error counter for each of the low side bridges, and one for the high side. The overcurrent detection is inactive during the blank pulse time for each bridge, to suppress spikes which can occur during switching. The high side comparator detects a short to GND or an overcurrent, whenever the voltage between VS and VT becomes higher than 0.15 V at any time, except for the blank time period which is logically ORed for both bridges. Here all transistors become switched off for the rest of the PWM cycle, because the bridge with the failure is unknown. The overcurrent flags can be cleared by disabling and re-enabling the chip either via the ENN pin or by sending a telegram with both current control words set to “0000”. In high side overcurrent conditions the user can determine which bridge sees the overcurrent, by selectively switching on only one of the bridges with each polarity (therefore the other bridge should remain programmed to “0000”). Overtemperature protection and diagnosis The circuit switches off all output power transistors during an overtemperature condition. The overtemperature flag should be monitored to detect this condition. The circuit resumes operation after cool down below the temperature threshold. However, operation near the overtemperature threshold should be avoided, if a high lifetime is desired. Overvoltage protection and ENN pin behavior During disable conditions the circuit switches off all output power transistors and goes into a low current shutdown mode. All register contents is cleared to “0”, and all status flags are cleared. The circuit in this condition can also stand a higher voltage, because the voltage then is not limited by the maximum power MOSFET voltage. The enable pin ENN provides a fixed threshold of ½ VCC to allow a simple overvoltage protection up to 40V using an external voltage divider (see schematic). +VM R1 for switch off at 26 - 29V: at VCC=5V: R1=100K; R2=10K at VCC=3.3V: R1=160K; R2=10K ENN R2 µC-Port (opt.) low=Enable, high=Disable Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 14 Chopper Principle Chopper cycle / Using the mixed decay feature The TMC246 uses a quiet fixed frequency chopper. Both coils are chopped with a phase shift of 180 degrees. The mixed decay option is realized as a self stabilizing system (pat. fi.), by shortening the fast decay phase, if the ON phase becomes longer. It is advised to enable the mixed decay for each phase during the second half of each microstepping half-wave, when the current is meant to decrease. This leads to less motor resonance, especially at medium velocities. With low velocities or during standstill mixed decay should be switched off. In applications requiring high resolution, or using low inductivity motors, the mixed decay mode can also be enabled continuously, to reduce the minimum motor current which can be achieved. When mixed decay mode is continuously on or when using high inductivity motors at low supply voltage, it is advised to raise the chopper frequency to 36kHz, because the half chopper frequency could be audible under these conditions. target current phase A actual current phase A on slow decay on fast decay slow decay oscillator clock resp. external clock mixed decay disabled mixed decay enabled When polarity is changed on one bridge, the PWM cycle on that bridge becomes restarted at once. Fast decay switches off both upper transistors, while enabling the lower transistor opposite to the selected polarity. Slow decay always enables both lower side transistors. Blank Time The TMC246 uses a digital blanking pulse for the current chopper comparators. This prevents current spikes, which can occur during switching action due to capacitive loading, from terminating the chopper cycle. The lowest possible blanking time gives the best results for microstepping: A long blank time leads to a long minimum turn-on time, thus giving an increased lower limit for the current. Please remark, that the blank time should cover both, switch-off time of the lower side transistors and turn-on time of the upper side transistors plus some time for the current to settle. Thus the complete switching duration should never exceed 1.5µs. The TMC246 allows to adapt the blank time to the load conditions and to the selected slope in four steps (the effective resulting blank times are about 200ns shorter in the non-A-type): Blank time settings BL2 BL1 Typical blank time GND GND 0.6 µs GND VCC 0.9 µs VCC GND 1.2 µs VCC VCC 1.5 µs Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 15 Classical non-SPI control mode (stand alone mode) The driver can be controlled by analog current control signals and digital phase signals. To enable this mode, tie pin SPE to GND. In this mode, the SPI interface is disabled and the SPI input pins have alternate functions. The internal DACs are forced to “1111”. Pin functions in stand alone mode Pin Stand alone mode name Function in stand alone mode SPE (GND) Tie to GND to enable stand alone mode ANN MDAN Enable mixed decay for bridge A (low = enable) SCK MDBN Enable mixed decay for bridge B (low = enable) SDI PHA Polarity bridge A (low = current flow from output OA1 to OA2) CSN PHB Polarity bridge B (low = current flow from output OB1 to OB2) SDO ERR Error output (high = overcurrent on any bridge, or overtemperature). In this mode, the pin is never tristated. ENN ENN Standby mode (high active), high causes a low power mode of the device. Setting this pin high also resets all error conditions. INA, INB INA, INB Current control for bridge A, resp. bridge B. Refer to AGND. The sense resistor trip voltage is 0.34V when the input voltage is 2.0V. Maximum input voltage is 3.0V. Input signals for microstep control in stand alone mode Attention: When transferring these waves to SPI operation, please remark, that the mixed decay bits are inverted when compared to stand alone mode. INA INB 90° 180° 270° 360° PHA (SDI) PHB (CSN) MDAN (ANN) MDBN (SCK) Use dotted line to improve performance at medium velocities Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 16 Calculation of the external components Sense Resistor Choose an appropriate sense resistor (RS) to set the desired motor current. The maximum motor current is reached, when the coil current setting is programmed to “1111”. This results in a current sense trip voltage of 0.34V when the internal reference or a reference voltage of 2V is used. When operating your motor in fullstep mode, the maximum motor current is as specified by the manufacturer. When operating in sinestep mode, multiply this value by 1.41 for the maximum current (Imax). RS = VTRIP / Imax In a typical application: RS = 0.34V / Imax RS: VTRIP: Imax: Current sense resistor of bridge A, B Programmed trip voltage of the current sense comparators Desired maximum coil current Examples for sense resistor settings Imax 723mA 790mA 870mA 1030mA 1259mA 1545mA RS 0.47Ω 0.43Ω 0.39Ω 0.33Ω 0.27Ω 0.22Ω High side overcurrent detection resistor RSH The TMC246 detects an overcurrent to ground, when the voltage between VS and VT exceeds 150mV. The high side overcurrent detection resistor should be chosen in a way that 100mV voltage drop are not exceeded between VS and VT, when both coils draw the maximum current. In a sinestep application, this is when sine and cosine wave have their highest sum, i.e. at 45 degrees, corresponding to 1.41 times the maximum current setting for one coil. In a fullstep application this is the double coil current. In a microstep application: RSH = 0.1V / (1.41 × Imax) In a fullstep application: RSH = 0.1V / (2 × Imax) RSH: Imax: High side overcurrent detection resistor Maximum coil current However, if the user desires to use higher resistance values, a voltage divider in the range of 10Ω to 100Ω can be used for VT. This might also be desired to limit the peak short to GND current, as described in the following chapter. Attention: A careful PCB layout is required for the sense resistor traces and for the RSH traces. Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 17 Making the circuit short circuit proof In practical applications, a short circuit does not describe a static condition, but can be of very different nature. It typically involves inductive, resistive and capacitive components. Worst events are unclamped switching events, because huge voltages can build up in inductive components and result in a high energy spark going into the driver, which can destroy the power transistors. The same is true when disconnecting a motor during operation: Never disconnect the motor during operation! There is no absolute protection against random short circuit conditions, but pre-cautions can be taken to improve robustness of the circuit: In a short condition, the current can become very high before it is interrupted by the short detection, due to the blanking during switching and internal delays. The high-side transistors allows up to 10A flowing for the selected blank time. The lower the external inductivity, the faster the current climbs. If inductive components are involved in the short, the same current will shoot through the low-side resistor and cause a high negative voltage spike at the sense resistor. Both, the high current and the voltage spikes are a danger for the driver. Thus there are a two things to be done, if short circuits are expected: 1. Protect SRA/SRB inputs using a series resistance 2. Increase RSH to limit maximum transistor current: Use same value as for sense resistors 3. Use as short as possible blank time The second measure effectively limits short circuit current, because the upper driver transistor with its fixed ON gate voltage of 7V forms a constant current source together with its internal resistance and RSH. A positive side effect is, that only one type of low ohmic resistor is required. The drawback is, that power dissipation increases slightly. A high side short detection resistor of 0.33 Ohms limits maximum high side transistor current to typically 4A. The schematic shows the modifications to be done. However, the effectiveness of these measures should be tested in the given application. VS RDIV RSH 100nF VT +VM 100R GND RSH=RSA=RSB RDIV values for Microstep: Fullstep: internal reference 27R 18R INA/INB up to3V 18R 12R CVM SRA 100R SRB 100R RSA RSB GND Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 18 Oscillator Capacitor The PWM oscillator frequency can be set by an external capacitor. The internal oscillator uses a 28kΩ resistor to charge / discharge the external capacitor to a trip voltage of 2/3 Vcc respectively 1/3 Vcc. It can be overdriven using an external CMOS level square wave signal. Do not set the frequency higher than 100kHz and do not leave the OSC terminal open! The two bridges are chopped with a phase shift of 180 degrees at the positive and at the negative edge of the clock signal. 1 fOSC ≈ 40 µs × COSC [nF] fOSC: COSC: PWM oscillator frequency Oscillator capacitor in nF Table of oscillator frequencies fOSC typ. 16.7kHz 20.8kHz 25.0kHz 30.5kHz 36.8kHz 44.6kHz COSC 1.5nF 1.2nF 1.0nF 820pF 680pF 560pF Please remark, that an unnecessary high frequency leads to high switching losses in the power transistors and in the motor. For most applications a chopper frequency slightly above audible range is sufficient. When audible noise occurs in an application, especially with mixed decay continuously enabled, the chopper frequency should be two times the audible range. For most applications we recommend a frequency of 36.8kHz. Pullup resistors on unused inputs The digital inputs all have integrated pull-up resistors, except for the ENN input, which is in fact an analog input. Thus, there are no external pull-up resistors required for unused digital inputs which are meant to be positive. Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 19 Slope Control Resistor The output-voltage slope of the full bridge outputs can be controlled to reduce noise on the power supply and on the motor lines and thus electromagnetic emission of the circuit. It is controlled by an external resistor at the SLP pin. Operational range: 0kΩ ≤ RSLP ≤ 100kΩ The SLP-pin can directly be connected to AGND for the fastest output-voltage slope (respectively maximum output current). In most applications a minimum external resistance of 10 KΩ is recommended to avoid unnecessary high switching spikes. Only for non-A-types the slope on the lower transistors is fixed (corresponding to a 5KΩ to 10KΩ slope control resistor). For applications where electromagnetic emission is very critical, it might be necessary to add additional LC (or capacitor only) filtering on the motor connections. For these applications emission is lower, if only slow decay operation is used. Please remark, that there is a trade off between reduced electromagnetic emissions (slow slope) and high efficiency because of low dynamic losses (fast slope). The following table and graph depict typical behavior measured from 15% of output voltage to 85% of output voltage. However, the actual values measured in an application depend on multiple parameters and may stray in a user application. Example for slope settings tSLP [ns] @ 10V tSLP [ns] @ 24V tSLP typ. 30ns 60ns 110ns 245ns 460ns RSLP 2.2KΩ 10KΩ 22KΩ 51KΩ 100KΩ 500 200 100 50 20 10 0 1 2 5 10 RSLP in KOhm Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG 20 50 100 TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 20 Absolute Maximum Ratings The maximum ratings may not be exceeded under any circumstances. Symbol Parameter Min Max Unit VS Supply voltage (A-type) 36 V VS Supply voltage (non-A-type) 30 V VMD Supply and bridge voltage max. 20000s (non-A-type: device disabled) 40 V VTR Power transistor voltage VOA-VBRA, VOBVBRB, VSA-VOA, VSB-VOB (A-type) 40 V VTR Power transistor voltage VOA-VBRA, VOBVBRB, VSA-VOA, VSB-VOB (non-A-type) 30 V VCC Logic supply voltage 6.0 V IOP Output peak current (10µs pulse) +/-7 A IOC Output current (continuous, one bridge) TA ≤ 85°C 1500 mA TA ≤ 105°C 1000 TA ≤ 125°C 800 -0.5 VI Logic input voltage -0.3 VCC+0.3V V VIA Analog input voltage -0.3 VCC+0.3V V IIO Maximum current to / from digital pins +/-10 mA VS-1V VS+0.3V V and analog inputs VVT Short-to-ground detector input voltage TJ Junction temperature -40 150 (1) °C TSTG Storage temperature -55 150 °C (1) Internally limited Electrical Characteristics Operational Range Symbol Parameter Min Max Unit TAI Ambient temperature industrial (1) -25 125 °C TAA Ambient temperature automotive -40 125 °C TJ Junction temperature -40 140 °C VS Bridge supply voltage (A-type) 7 34 V VS Bridge supply voltage (non-A-type) 7 28.5 V VCC Logic supply voltage 3.0 5.5 V fCLK Chopper clock frequency 50 kHz RSLP Slope control resistor 110 KΩ 0 (1) The circuit can be operated up to 140°C, but output power derates. Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 21 DC Characteristics DC characteristics contain the spread of values guaranteed within the specified supply voltage and temperature range unless otherwise specified. Typical characteristics represent the average value of all parts. Logic supply voltage: VCC = 3.0 V ... 5.5 V, Junction temperature: TJ = -40°C … 150°C, Bridge supply voltage : VS = 7 V … 34 V (unless otherwise specified) Symbol Parameter Conditions ROUT,Sink RDSON of sink-transistor Typ Max Unit TJ = 25°C VS ≥ 8V 0.12 0.19 Ω ROUT,Source RDSON of source-transistor TJ = 25°C VS ≥ 8V 0.22 0.36 Ω ROUT,Sink TJ =150°C VS ≥ 8V 0.20 0.26 Ω TJ =150°C VS ≥ 8V 0.37 0.47 Ω TJ = 25°C IOXX = 1.05A 0.84 1.12 V RDSON of sink-transistor max. ROUT,Source RDSON of source-transistor max. VDIO Diode forward voltages of Oxx MOSFET diodes Min VCCUV VCC undervoltage 2.5 2.7 2.9 V VCCOK VCC voltage o.k. 2.7 2.9 3.0 V 0.85 1.35 mA 0.45 0.75 mA 37 70 µA ICC VCC supply current fosc = 25 kHz ICCSTB VCC supply current standby ICCSD VCC supply current shutdown VSUV VS undervoltage 5.5 5.9 6.2 V VCCOK VS voltage o.k. 6.1 6.4 6.7 V ISSM ENN = 1 VS supply current with fastest slope setting (static state) VS = 14V, ISSD VS supply current shutdown or standby VS = 14V VIH High input voltage (SDI, SCK, CSN, BL1, BL2, SPE, ANN) VIL 6 mA RSLP = 0K 50 µA 2.2 VCC + 0.3 V V Low input voltage (SDI, SCK, CSN, BL1, BL2, SPE, ANN) -0.3 0.7 V VIHYS Input voltage hysteresis (SDI, SCK, CSN, BL1, BL2, SPE, ANN) 100 300 500 mV VOH High output voltage (output SDO) -IOH = 1mA VCC – 0.6 VCC – 0.2 VCC V VOL Low output voltage (output SDO) IOL = 1mA 0 0.1 0.4 V -IISL Low input current (SDI, SCK, CSN, BL1, BL2, SPE, ANN) VI = 0 VCC = 3.3V VCC = 5.0V 2 70 µA µA µA VENNH High input voltage threshold (input ENN) VEHYS Input voltage hysteresis Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG 28 10 25 1/2 VCC 0.1 TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 22 (input ENN) VENNH VOSCH High input voltage threshold (input OSC) tbd 2/3 VCC tbd V VOSCL Low input voltage threshold (input OSC) tbd 1/3 VCC tbd V VVTD VT threshold voltage (referenced to VS) -130 -155 -180 mV VTRIP SRA / SRB voltage at DAC=”1111” 315 350 385 mV VSRS SRA / SRB overcurrent detection threshold 570 615 660 mV SRA / SRB comparator offset voltage -10 0 10 mV 175 264 300 kΩ VSROFFS RINAB INA / INB input resistance internal ref. or 2V at INA / INB Vin ≤ 3 V AC Characteristics AC characteristics contain the spread of values guaranteed within the specified supply voltage and temperature range unless otherwise specified. Typical characteristics represent the average value of all parts. Bridge supply voltage: VS = 14.0V, Logic supply voltage: VCC = 5.0V, Ambient temperature: TA = 27°C Symbol Parameter fOSC Oscillator frequency using internal oscillator tRS, tFS tRS, tFS tRS, tFS TBL TONMIN Rise and fall time of outputs Oxx with RSLP=0 Rise and fall time of outputs Oxx with RSLP = 25KΩ Rise and fall time of outputs Oxx with RSLP = 50KΩ Conditions Min Typ Max Unit COSC = 1nF ±1% 20 25 31 kHz Vo 15% to 85% 25 ns 125 ns 250 ns IOXX = 800mA Vo 15% to 85% IOXX = 800mA Vo 15% to 85% IOXX = 800mA Effective Blank time BL1, BL2 = VCC Minimum PWM on-time BL1, BL2 = GND 1.35 1.5 1.65 0.7 µs µs Thermal Protection Symbol TJOT TJOTHYS TJWT TJWTHYS Parameter Conditions Thermal shutdown Min Typ Max Unit 145 155 165 °C TJOT hysteresis Prewarning temperature TJWT hysteresis Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG 15 135 145 15 °C 155 °C °C TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 23 Thermal Characteristics Symbol Parameter Conditions Typ Unit RTHA12 Thermal resistance bridge transistor junction to ambient, one bridge chopping, fixed polarity soldered to 2 layer PCB 88 °K/W RTHA22 Thermal resistance bridge transistor junction to ambient, two bridges chopping, fixed polarity soldered to 2 layer PCB 68 °K/W RTHA14 Thermal resistance bridge transistor junction to ambient, one bridge chopping, fixed polarity soldered to 4 layer PCB (pessimistic) 84 °K/W RTHA24 Thermal resistance bridge transistor junction to ambient, two bridges chopping, fixed polarity soldered to 4 layer PCB (pessimistic) 51 °K/W Typical Power Dissipation at high load / high temperature Coil: Chopping with: LW = 10mH, RW = 5.0Ω tDUTY = 33% ON, only slow decay Current Current Ambient both brid- one bridge temperature ges on on TA Motor supply Slope voltage tSLP VM Chopper frequency fCHOP Typ total power dissipation PD 560 mA 560 mA 16 V 16 V 14 V 14 V 28 V 28 V 25 KHz 25 KHz 20 KHz 20 KHz 25 KHz 25 KHz 490 mW 450 mW 350 mW 340 mW 1000 mW 1100 mW 1000 mA - 800 mA 800 mA 1500 mA 105 °C 105 °C 125 °C 125 °C 70 °C 70 °C 400 ns 400 ns 60ns 60ns 60ns 60ns Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 24 SPI Interface Timing tES ENN CSN t1 tCL tCH t1 t1 SCK tDU bit11 SDI tDH bit10 bit0 tD SDO tZC bit11 bit10 bit0 Propagation Times (3.0 V ≤ VCC ≤ 5.5 V, -40°C ≤ Tj ≤ 150°C; VIH = 2.8V, VIL = 0.5V; tr, tf = 10ns; CL = 50pF, unless otherwise specified) Symbol fSCK Parameter SCK frequency Conditions Min ENN = 0 DC Typ Max Unit 4 MHz t1 SCK stable before and after CSN change 50 ns tCH Width of SCK high pulse 100 ns tCL Width of SCK low pulse 100 ns tDU SDI setup time 40 ns tDH SDI hold time 50 ns tD SDO delay time tZC CSN high to SDO high impedance tES ENN to SCK setup time tPD CSN high to OA / OB output polarity change delay tLD Load indicator valid after OA / OB output polarity change CL = 50pF *) **) 40 100 ns 50 ns 30 ns 3 tOSC + 4 µs 5 7 µs *) SDO is tristated whenever ENN is inactive (high) or CSN is inactive (high). **) Whenever the PHA / PHB polarity is changed, the chopper is restarted for that phase. However, the chopper does not switch on, when the SRA resp. SRB comparator threshold is exceeded upon the start of a chopper period. Using the SPI interface The SPI interface allows either cascading of multiple devices, giving a longer shift register, or working with a separate chip select signal for each device, paralleling all other lines. Even when there is only one device attached to a CPU, the CPU can communicate with it using a 16 bit transmission. In this case, the upper 4 bits are dummy bits. SPI Filter To prevent spikes from changing the SPI settings, SPI data words are only accepted, if their length is at least 12 bit. Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 25 ESD Protection Please be aware, that the TMC246 is an ESD sensitive device due to integrated high performance MOS transistors. ESD sensitive device If the ICs are manually handled before / during soldering, special precautions have to be taken to avoid ESD voltages above 100V HBM (Human body model). For automated SMD equipment the internal device protection is specified with 1000V CDM (charged device model), tbf. When soldered to the application board, all inputs and outputs withstand at least 1000V HBM. Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG TMC246 / TMC246A DATA SHEET (V2.03 / Nov. 6th, 2006) 26 Application Note: Extending the Microstep Resolution For some applications it might be desired to have a higher microstep resolution, while keeping the advantages of control via the serial interface. The following schematic shows a solution, which adds two LSBs by selectively pulling up the SRA / SRB pin by a small voltage difference. Please remark, that the lower two bits are inverted in the depicted circuit. A full scale sense voltage of 340mV is assumed. The circuit still takes advantage of completely switching off of the coils when the internal DAC bits are set to “0000”. This results in the following comparator trip voltages: Current setting Trip voltage (MSB first) 0000xx 0V 000111 5.8 mV 000110 11.5 mV 000101 17.3 mV 000100 23 mV ... 111101 334.2 mV 111100 340 mV SPI bit DAC bit SPI bit DAC bit 15 /B1 7 A2 14 /B0 6 PHA 13 /A1 5 MDB 12 /A0 4 B5 11 MDA 3 B4 10 A5 2 B3 9 A4 1 B2 SCK SCK SDI SDI TMC236 / TMC239 SRA SDO 110R 4.7nF opt. CSN /CS 47K 47K RS 47K +VCC 100K /OE C2 /MR C1 DS1D Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 /DACA.0 /DACA.1 /DACB.0 /DACB.1 Free for second TMC239 Q7' 74HC595 Vcc = 5V C SDO Q D 1/2 74HC74 Note: Use a 74HC4094 instead of the HC595 to get rid of the HC74 and inverter Please see the FAQ document for more application information. i SPI is a trademark of Motorola Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG 8 A3 0 PHB