14
462
the motor windings and a power stage to drive the motor. The translator
generates three different sequences selected by the half/full step input. These
are normal (two phases energized), wave drive (one phase energized) and half
step (alternately one phase energized/two phases energized).
A common on-board oscillator drives the dual chopper. It supplies pulses
which set two flip-flops. When the current in a winding reaches the set peak
value a corresponding comparator resets its flip-flop, shutting down the output
stage until the next oscillator pulse comes along.
Because the windings in the motor store energy, current will continue to flow
through the windings during the off period. The peak current for both windings
is set by the current adjust input.
The output stage consists of dual full bridge drivers. The IB462H can be
disabled by a logic LOW signal on the enable input. Ultra fast recovery
flyback rectifiers are used to improve efficiency and help reduce noise.
O u t p u t W a v e S e q u e n c e s
The IB462H generates phase sequences for normal, wave, and half step
modes. The state diagram and output waveforms are shown below. In all
modes the transition occurs on the falling edge of the Step Clock signal.
N o r m a l M o d e
In normal drive mode two phases are energized at all times. This mode is
selected by sinking the Half/Full Step input.
W a v e M o d e
In wave drive mode one phase is energized at a time. This mode is enabled by
selecting full step mode when the IB462H is in an even numbered state. To
select this mode, power the IB462H, send a single step clock pulse then sink
the Half/Full Step input.
Figure 1.4.2: Normal Mode Phase Sequence
1
3
5
7
2
4
6
8
1
3
5
7
1
3
5
7
1
STEP CLOCK
PHASE A
PHASE B
PHASE A
PHASE B
