AN1627 Freescale Semiconductor / Motorola, AN1627 Datasheet - Page 15

• Manufacturer Part Number: AN1627
• Description: Low Cost High Efficiency Sensorless Drive for Brushless dc Motor Using MC68HC (7)05MC4
• Manufacturer: Freescale Semiconductor / Motorola

Freescale Semiconductor, Inc.
the commutation, disabled before the successive commutation (OC ISR) or disabled when the edge of
the Zero Crossing signal is detected by the IC function (see Figure 5-3.). If a zero crossing edge is
detected, then the time interval from the commutation is calculated and condition the 90°<
< 180° is

evaluated. If this condition is met six times and the current peak is within the limit then the program flow
continues. The following subroutines are called: Speed Setting & DC-Bus voltage sensing,
Commutation.
The Figure 5-2. shows the moment when the zero crossing points can be sensed. The actual angle
is

less than 90°, so the entry condition to the Running stage is not met and the DC-Bus voltage is
decreased further.
5.2.3
BODY
This routine performs the Running stage. Speed Setting & DC-Bus voltage sensing and Commutation
subroutines are called. The zero crossing feedback is handled and the angle
is evaluated. If no

feedback is captured between commutations, then the zero crossing comparator feedback (TCAP2 pin)
is sampled directly, just before the commutation takes place (see Figure 5-3.,
samples).
Figure 5-3.
Control signals
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AN1627
MOTOROLA
REV 0.2
15