L6238S View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6238S' PDF : 31 Pages View PDF
L6238S
Figure 2-5
POR=0
FROM ANY STATE
STATE=1
DRIVERS OFF
MIN CLOCK DELAY
PERIOD STOP
DELAY STOP
MASK STOP
SEQINC=1 &
OUTENA=0
RUN/BRK=X
INT START-UP DISABLED
MIN CLOCK DELAY
LOAD MIN DELAY
LOAD MIN MASK
RUN/BRK=1 &
OUTENA=1
SEQINC=0
DRIVERS ON
PERIOD COUNT
DELAY COUNT
SEQINC=1
STATE=STATE+1
MASK COUNT
SEQINC=0
BEMF
BEMF
LOAD DELAY=PERIOD
LOAD MASK=PERIOD
RESET PERIOD
PERIOD COUNT
DELAY COUNT**
MASK COUNT
SEQINC=1
SEQINC=1
FROM ANY STATE
WITH SEQ_INC=0
STATE=STATE+1
RETURN TO
PREVIOUS STATE
(CHANGING SEQINC=1)
*VALID IF SEQINC=0, AND DELAY TIMES OUT
D95IN313
**CLOCK DELAY=F(TDLY_[2:0])
WHEN BEMF PERIOD <3.3ms @ 10MHz (SPEED >12.7Hz FOR 8 POLES)
If zero crossings are detected, the sequencer will
automatically lock on to the proper phase.
This resynchronization will take effect with the
motor speed running as low as typically 30% of
it’s nominal value.
2.5 External Sequencing
Although the user-defined Start-Up Algorithm is
flexible and will consistently spin up a motor with
no external interaction, the possibility exists
where certain applications might require complete
microprocessor control of start-up.
The L6238S offers this capability via the SE-
QUENCE INCREMENT input. Referring to figure
2-5, during initial power-up with Output Enable
low, the controller is in the ”Hold and Wait for De-
cision” state. If the SEQUENCE INCREMENT pin
is brought high during this state, the Auto StartUp
Algorithm is disabled and the sequencer can be
controlled externally.
When Output Enable and Run/Brake are
brought high, the sequencer is incremented on
each positive transition o the SEQUENCER IN-
12/31
CREMENT pin. During the time that this pin is
high, all Bemf information is masked out. When it
is low, the Bemf information can be detected nor-
mally after the internal mask time. The minimum
mask time is 192/Sys_Clk (i.e. with Sys_Clk =
10MHz, min. mask = 19.2µs) Therefore to insure
that the sequencer is under complete control of
the state machine, the time that the SEQUENCE
INCREMENT pin is held low should be much less
then the min. mask time, but greater then 1µs.
When the motor has reached a predetermined
speed, the SEQUENCE INCREMENT pin can be
left low and the L6238S Motor Control logic will
take over and automatically spin up the motor to
the desired speed
.
3.0 START-UP ALGORITHMS
3.1 Spin-Up Operation
The spin operation can be separated into 3 parts:
1) Open Loop Start-Up - The object is to create
motion in the desired direction so that the Bemf
voltages at the 3 motor terminals can provide reli-
able information enabling a transition to closed
loop operation.
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