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NXP Semiconductors
Application Note
Document Number: AN5194
Rev. 1.0, 7/2016
© 2016 NXP B.V.
1 Introduction
NXP offers a wide assortment of integrated H-Bridge devices to drive
brushed DC motors. In this application note, the MC34932 and MC33932
monolithic dual H-Bridge power integrated circuits are selected to discuss
thermal calculations. The same principles can be applied to all NXP
integrated H-Bridge motor drivers.
In the MC34932/MC33932, each H-Bridge is able to control inductive
lo
ads with currents up to a peak of 5.0 A. The RMS current capability is
sub
ject to the degree of heat-sinking provided to the device package. It
has an internal peak-current limiting (regulation), which gets activated at
load currents above 6.5 A ±1.5 A. Output loads can be pulse-width
modu
lated (PWMed) at frequencies up to 11 kHz (MC33932EK and
MC34932EK) or up to
20 kHz (MC34932SEK). A load current feedback
feature provides a proportional (0.24% of the load current) current output
suitable for monitoring by a microcontroller’s A/D input. A Status Flag
output reports undervoltage, overcurrent, and overtemperature fault
conditions. Two independent inputs provide polarity control of two
half-bridge totem pole outputs. Two independent disable inputs are
provided to force the H-Bridge outputs to tri-state (high-impedance off
state). A simplified application diagram is shown in Figure 1.
Power dissipation and thermal calculations for
H-Bridge motor drivers
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
3 Differentiating Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
4 Power dissipation calculation. . . . . . . . . . . . . . . . . . . . . . . . . . . .4
5 Junction temperature estimation . . . . . . . . . . . . . . . . . . . . . . . . .6
6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
7 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
