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non-overlapping output signals
that stop the high- and low-side
conducting at the same time.
Ideally, the n- and p-channel
MOSFETs should have the same on
resistance (RDSon) and total gate
charge QG to obtain the optimal
switching performance. Therefore,
while it would be good to choose
a complementary pair of MOSFETs
to match these parameters, in
reality this is impossible due to
their different construction; the
chip size of the p-channel device
must be two to three times that of
the n-channel to match the RDSon
performance. But the larger the chip
size, the larger the effect of QG.
Thus, when selecting the MOSFETs,
it is important to decide whether
RDSon or QG will have the biggest
impact on switching performance
and choose accordingly.
Fault detection
Exceeding the motor’s maximum
allowable torque loading can cause
Fig. 2: Control diagram of motor driver
Fig. 3: Single-phase BLDC motor driver schematic diagram
the driver’s components. To avoid
this, a dead-band delay can be
implemented using the CWG’s
counter registers. This provides
36 l New-Tech Magazine Europe