TMC5161 DATASHEET (Rev. 1.01 / 2018-NOV-20)
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Figure 28.3 Thermal distribution 2.8A RMS operation running spreadCycle
Especially when device is to be operated near its maximum thermal limits, care has to be taken to
provide a good thermal design of the PCB layout in order to avoid overheating of the power MOSFETs
integrated into the TMC5161. As the TMC5161 uses discrete MOSFETs, power dissipation in each
MOSFET needs to be looked over carefully. The actual values depend on the duty cycle and the die
temperature. The thermal characteristics and the sample layout are intended as a guideline for your
own board layout. In case, the driver is to be operated at high current levels, special care should be
taken to spread the heat generated by the driver power bridges efficiently within the PCB.
Worst case power dissipation for the individual MOSFET is in standstill or at low velocity, with one
coil operating at the maximum current, because one full bridge in this case takes over the full current.
This scenario can be avoided with power down current reduction and current reduction in case slow
movements (<1Hz fullstep frequency) are required. As single MOSFET temperatures cannot be
monitored within the system, it is a good practice to react to the temperature pre-warning by
reducing motor current, rather than relying on the overtemperature switch off.
The MOSFET (and bond wire) temperature should not exceed 150°C, despite temperatures up to 200°C
will not immediately destroy the devices. But the package plastics will apply strain onto the bond
wires, so that cyclic, repetitive exposure to temperatures above 150°C may damage the electrical
contacts and increase contact resistance and eventually lead to contract break.
Check MOSFET temperature under worst case conditions not to exceed 150°C using a thermal camera
to validate your layout. Please carefully check your layout against the sample layout or the layout of
the TMC5161 evaluation board on the TRINAMIC website in order to ensure proper cooling of the IC!
www.trinamic.com
TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
