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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

Register

Value

Comments

7

6

5

4

3

2

1

0

MPAR

TES1 TES0 OE5

OE4

OE3

OE2

OE1

OE0

Outputs 0, 2, 4 are HIGH channels

Outputs 1, 3, 5 are LOW channels

0

0

1

0

1

0

1

0

MCRA

MOE CKE

SR

DAC V0C1 SWA

PZ

DCB

The motor runs in autoswitched

mode,

current mode, sensorless mode.

1

1

0

0

1

1

X

X

MCRB

Res

CPB HDM SDM OCV OS2

OS1

OS0

PWM after end of demagnetization:

on HIGH channels.

0

S

S

S

S

S

0

1

MCRC

OI

HZ

SZ

SC

SPLG VR2

VR1

VR0

Hardware Z event

Sampling at the end of PWM off time

0

1

0

0

0

X

X

X

MDTG

PCN DTE DTG5 DTG4 DTG3 DTG2 DTG1 DTG0

Only PWM U is output to the PWM

manager

No Dead time generator

0

0

0

0

0

0

0

0

MPHST

IS1

IS0

OO5

OO4 OO3 OO2 OO1 OO0

Input selection and output data

change at each step.

S

S

S

S

S

S

S

S

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.