Datasheet

TMC260/A and TMC261 DATASHEET (Rev. 2.10 / 2016-JUL-14) 43
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15 Layout Considerations
The PCB layout is critical to good performance, because the environment includes both high-
sensitivity analog signals and high-current motor drive signals.
15.1 Sense Resistors
The sense resistors are susceptible to ground differences and ground ripple voltage, as the microstep
current steps result in voltages down to 0.5mV. No current other than the sense resistor currents
should flow through their connections to ground. Place the sense resistors close to chip with one or
more vias to the ground plane for each sense resistor.
The sense resistor layout is also sensitive to coupling between the axes. The two sense resistors
should not share a common ground connection trace or vias, because PCB traces have some
resistance.
15.2 Power MOSFET Outputs
The OA and OB dual pin outputs on the TMC260 and TMC261 are directly connected electrically and
thermally to the drain of the MOSFETs of the power stage. A symmetrical, thermally optimized layout
is required to ensure proper heat dissipation of all MOSFETs into the PCB. Use thick traces and areas
for vertical heat transfer into the GND plane and enough vias for the motor outputs.
The printed circuit board should have a solid ground plane spreading heat into the board and
providing for a stable GND reference. All signals of the TMC260 and TMC261 are referenced to GND.
Directly connect all GND pins to a common ground area.
The switching motor coil outputs have a high dV/dt, so stray capacitive coupling into high-impedance
signals can occur, if the motor traces are parallel to other traces over long distances.
15.3 Power Filtering
The 470nF ceramic filtering capacitor on 5VOUT should be placed as close as possible to the 5VOUT
pin, with its GND return going directly to the nearest GND pin. Use as short and as thick connections
as possible. A 100nF filtering capacitor should be placed as close as possible from the VS pin to the
ground plane. The motor supply pins, VSA and VSB, should be decoupled with an electrolytic (>47 μF
is recommended) capacitor and a ceramic capacitor, placed close to the device.