The three phase application shown in Figure 35 is an open
loop motor controller with full wave, six step drive. The
upper power switch transistors are Darlington PNPs while
the lower switches are N−Channel power MOSFETs. Each
of these devices contains an internal parasitic catch diode
that is used to return the stator inductive energy back to the
power supply. The outputs are capable of driving a delta or
wye connected stator, and a grounded neutral wye if split
supplies are used. At any given rotor position, only one top
and one bottom power switch (of different totem poles) is
enabled. This configuration switches both ends of the stator
winding from supply to ground which causes the current
flow to be bidirectional or full wave. A leading edge spike
is usually present on the current waveform and can cause a
current−limit error. The spike can be eliminated by adding