TMC260-PA Datasheet, PDF (5/53 Pages) TRINAMIC Motion Control GmbH & Co. KG. – POWER DRIVER FOR STEPPER MOTORS

TMC260/A and TMC261 DATASHEET (Rev. 2.10 / 2016-JUL-14)
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In addition to these performance enhancements, TRINAMIC motor drivers also offer safeguards to
detect and protect against shorted outputs, open-circuit output, overtemperature, and undervoltage
conditions for enhancing safety and recovery from equipment malfunctions.
1.2 Control Interfaces
There are two control interfaces from the motion controller to the motor driver: the SPI serial
interface and the STEP/DIR interface. The SPI interface is used to write control information to the chip
and read back status information. This interface must be used to initialize parameters and modes
necessary to enable driving the motor. This interface may also be used for directly setting the currents
flowing through the motor coils, as an alternative to stepping the motor using the STEP and DIR
signals, so the motor can be controlled through the SPI interface alone.
The STEP/DIR interface is a traditional motor control interface available for adapting existing designs
to use TRINAMIC motor drivers. Using only the SPI interface requires slightly more CPU overhead to
look up the sine tables and send out new current values for the coils.
1.2.1 SPI Interface
The SPI interface is a bit-serial interface synchronous to a bus clock. For every bit sent from the bus
master to the bus slave, another bit is sent simultaneously from the slave to the master.
Communication between an SPI master and the TMC260 or TMC261 slave always consists of sending
one 20-bit command word and receiving one 20-bit status word.
The SPI command rate typically corresponds to the microstep rate at low velocities. At high velocities,
the rate may be limited by CPU bandwidth to 10-100 thousand commands per second, so the
application may need to change to fullstep resolution.
1.2.2 STEP/DIR Interface
The STEP/DIR interface is enabled by default. Active edges on the STEP input can be rising edges or
both rising and falling edges, as controlled by another 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.
On each active edge, the state sampled from the DIR input 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. During microstepping, a step impulse with a low state on DIR increases the
microstep counter and a high decreases the counter by an amount controlled 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 Mechanical Load Sensing
The TMC260 and TMC261 provide stallGuard2 high-resolution load measurement for determining the
mechanical load on the motor by measuring the back EMF. In addition to detecting when a motor
stalls, this feature can be used for homing to a mechanical stop without a limit switch or proximity
detector. The coolStep power-saving mechanism uses stallGuard2 to reduce the motor current to the
minimum motor current required to meet the actual load placed on the motor.
1.4 Current Control
Current into the motor coils is controlled using a cycle-by-cycle chopper mode. Two chopper modes
are available: a traditional constant off-time mode and the new spreadCycle mode. spreadCycle mode
offers smoother operation and greater power efficiency over a wide range of speed and load.
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