IRSM836-035MA Datasheet, PDF (14/19 Pages) International Rectifier – Integrated Power Module for Small Appliance Motor Drive Applications

IRSM836-035MA
PCB Example
Figure 7 below shows an example layout for the application PCB. The effective area of the V+ top-layer
copper plane is ~3cm² in this example. For an FR4 PCB with 1oz copper, R_th(J-A) is about 40°C/W. A lower R_th(J-A)
can be achieved using thicker copper and/or additional layers.
Module
Figure 7: PCB layout example and corresponding thermal image
At the module’s typical operating conditions, dV/dt of the phase node voltage is influenced by the load
capacitance which includes parasitic capacitance of the PCB, MOSFET output capacitance and motor winding
capacitance. To turn off the MOSFET, the load capacitance needs to be charged by the phase current. For the
IRMCS1171 reference design, turn-off dV/dt ranges from 2 to 5 V/ns depending on the phase current magnitude.
Turn-on dV/dt is influenced by PCB parasitic capacitance and motor winding capacitance and typically ranges
from 4 to 6 V/ns. The MOSFET turn-on loss combined with the complimentary body diode reverse recovery loss
comprises the majority of the total switching losses. Two-phase modulation can be used to reduce switching
losses and run the module at higher phase currents.
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© 2013 International Rectifier
February 3, 2013