L6238S datasheet(13/31 Pages) STMICROELECTRONICS

13 / 31 page

2) Closed Loop Start-Up - The Bemf voltage

zerocrossings provide timing information so that

the motor can be accelerated to steady state

speed.

3) Steady-State Operation - The Bemf voltage

zero-crossings provide timing information for pre-

cision speed control.

The L6238S contains features that offer flexible

control over the start-up procedure. Either the on-

board Auto-Start Algorithm can be used to control

the start-up sequence or more sophisticated ex-

tenal start-up algorithms can be developed using

the Serial Port and key control/sense functions

brought out to pins.

3.2 Auto-Start Algorithm

When initially powered up, the controller defaults

to the internal AutoStart Mode. When Run/Brake

is low, the L6238S is in brake mode, and the

Auto-Start Algorithm is reset. In the brake mode,

all of the lower DMOS drivers are ON, and the up-

per drivers are OFF.

The Auto-Start Algorithm is based on an Align &

Go approach and can be visualized by referring to

Figure 3-1. Shown are the Run/Brake control sig-

nals, sequencer function, and the three output

voltage waveforms.

Referring to figure 3-1, the following is the se-

quence of events during Auto-Start:

With Output Enable =1, Run/Brake =0

- State Machine is set to State 1 with the drivers

Trisatted.

Alignment Phase (1)

Run/Brake =1

- Output Stage is sequenced to State 2 and the

drivers energized with OUTPUT A high and

OUTPUT C low for 64/Falign seconds.

Alignment Phase (2)

- Output Stage is double sequenced to State 4

with OUTPUT B high and OUTPUT A low for

STATE 2

A=HIGH

B=FLOAT

C=LOW

STATE 4

A=LOW

B=HIGH

C=FLOAT

STATE 6

A=FLOAT

B=LOW

C=HIGH

500ms/DIV

* FALIGN=90Hz

AOUT

10V

BOUT

10V

COUT

10V

ALIGNMENT

DOUBLE INCREMENTS

*0.711s

*2.133s

RUN/BRAKE

SEQUENCER

D95IN314

Figure 3-1: Align+Go

L6238S

13/31

L6238S Datasheet(PDF) 13 Page - STMicroelectronics

L6238S Datasheet(HTML) 13 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Datasheet Download

Link URL