TMC236_1 Datasheet, PDF(8/27 Page) TRINAMIC Motion Control GmbH & Co. KG. – High current, low power dissipation microstep stepper motor driver with protection / diagnostics and SPI Interface

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TMC236_1 Datasheet, PDF (8/27 Pages) TRINAMIC Motion Control GmbH & Co. KG. – High current, low power dissipation microstep stepper motor driver with protection / diagnostics and SPI Interface

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TMC236/A DATA SHEET (V2.06 / 2009-Jul-30)

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 systemâs GND-plane. Tie the TMC236âs AGND and GND to the GND plane. Additionally,

use enough filtering capacitors located near to the boardâs power supply input and small ceramic

capacitors near to the power supply connections of the TMC236. 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

100nF

GND

RDIV

100R

+VM

VSA

TMC236/

TMC246 VSB

BRA

BRB

SRA

SRB

AGND

optional filter

100R

3.3 -

10nF

CVM

RSA

RSB

GND-

Plane

GND

▷