Book Analog Interfacing to Embedded Microprocessors
can’t do any damage.
Shoot-through can also be caused by the driver transistors themselves.
Figure 7.13 shows one half of an H-bridge driver constructed with MOSFET
transistors. MOSFETs have a fairly high capacitance between the gate termi-
nal and both the other terminals (source and drain). In the figure, the capac-
itance is represented by the capacitance C, between the gate and drain of Q2.
This capacitance is usually on the order of a few tens of picofarads for a typical
MOSFET used in a motor application.
If transistor Q1 turns on to apply voltage to one side of the motor (the
transistor opposite Q2, not shown, on the other side of the bridge would turn
on as well), there will be a voltage spike at the junction of the drains of Q1
and Q2. This voltage spike will be coupled to the gate of Q2 by the capaci-
tance C. If the impedance of the device driving the gate of Q2 is high enough,
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