3-Phase Sinusoidal Motor Controller

A4923

7

Allegro MicroSystems, LLC

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Sine Mode

When the motor is stopped, a Hall Timeout error exists since the

hall-transition timer has timed out. When a start signal is applied

via the STARTn terminal, the motor is enabled in trapezoidal

mode. When two consecutive hall transitions do not overflow the

hall-transition timer, the Hall Timeout error is cleared and the

drive switches to sinusoidal mode.

The sine modulation profile is stored in a digital look-up table.

The sine modulation value is updated from the profile 192 times

per electrical revolution. At each hall transition, which occurs

every 60° or every 32 steps, the profile index is forced to the

appropriate step. It is then advanced the successive 32 steps with

a timer set internally using the previous hall transition period.

The motor outputs are generated as follows (phase advance is not

shown to simplify this diagram):

60º

60º

60º

60º

60º

60º

60º

60º

60º

60º

60º

60º

HA

Forward

Reverse

Motor

Position

from Hall

Inputs

Trapezoidal

Drive (startup) -

Motor Terminal

Voltage

Sine Drive -

Internal Sine

Modulation

Signal

SA

SA

HB

SB

SB

HC

SC

SC

Figure 1: Motor Outputs