AN2009 datasheet(35/39 Pages) STMICROELECTRONICS

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PWM MANAGEMENT FOR 3-PHASE BLDC MOTOR DRIVES USING THE ST7MC

8 CONFIGURATION EXAMPLE

This section gives a configuration example for a six-step 120° motor drive for a PM BLDC

motor in sensorless, current and autoswitched mode. The sensorless control method used

would be the ST method.

The configuration registers can be divided in two parts: Table 4 lists the configuration bits that

only need to be written once, Table 5 gives the step-dependent configuration bits. The regis-

ters in Table 2 must be updated within each commutation interrupt routine in order to select

the configuration for the next step.

Table 4. General Configuration Registers

Value

Comments

MPAR

TES1 TES0 OE5

OE4

OE3

OE2

OE1

OE0

Outputs 0, 2, 4 are HIGH channels

Outputs 1, 3, 5 are LOW channels

MCRA

MOE CKE

DAC V0C1 SWA

DCB

The motor runs in autoswitched

mode,

current mode, sensorless mode.

MCRB

Res

CPB HDM SDM OCV OS2

OS1

OS0

PWM after end of demagnetization:

on HIGH channels.

MCRC

SPLG VR2

VR1

VR0

Hardware Z event

Sampling at the end of PWM off time

MDTG

PCN DTE DTG5 DTG4 DTG3 DTG2 DTG1 DTG0

Only PWM U is output to the PWM

manager

No Dead time generator

MPHST

IS1

IS0

OO5

OO4 OO3 OO2 OO1 OO0

Input selection and output data

change at each step.

Notes:

- Bits marked with X depend on the motor and / or the application:

PZ depends on the noise present in the application,

DCB depends on the motor symmetry;

VR[2:0] bits depend on the noise level on the BEMF input pins.

- Bits marked with S have to be modified after each commutation (step dependent configuration). These

bits are summarized in Table 4. Those bits are taken in account only at the next commutation event.

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