mc68hc908mr24 Freescale Semiconductor, Inc, mc68hc908mr24 Datasheet - Page 152

• Manufacturer Part Number: mc68hc908mr24
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Pulse-Width Modulator for Motor Control
Advance Information
152
Whenever an input to a dead-time generator transitions, a dead-time is
inserted (for example, both PWMs in the pair are forced to their inactive
state). The bottom PWM signal is generated from the top PWM and the
dead-time. In the case of output control enabled, the odd OUTx bits
control the top PWMs, the even OUTx bits control the bottom PWMs with
respect to the odd OUTx bits (see Table 9-6).
effects of the dead-time insertion.
As seen in
dead-time is inserted. The active pulse widths are reduced. For
example, in
the ideal waveform (with no dead-time) has pulse widths equal to four.
However, the actual pulse widths shrink to two after a dead-time of two
was inserted. In this example, with the prescaler set to divide by one and
center-aligned operation selected, this distortion can be compensated
for by adding or subtracting half the dead-time value to or from the PWM
register value. This correction is further described in
Correction with Motor Phase Current Polarity
Further examples of dead-time insertion are shown in
Figure
duty cycle boundaries (near 0 percent and 100 percent duty cycles).
Figure 9-16
smaller than the dead time.
Pulse-Width Modulator for Motor Control (PWMMC)
9-16.
Figure
Figure
shows the effects of dead-time insertion on pulse widths
Figure 9-15
9-14, some pulse width distortion occurs when the
9-14, when the PWM value register is equal to two,
shows the effects of dead-time insertion at the
Figure 9-14
MC68HC908MR24
Sensing.
Freescale Semiconductor
9.6.3 Top/Bottom
Figure 9-15
shows the
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Rev. 4.1
and