AN1139 STMicroelectronics, AN1139 Datasheet - Page 12

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AN1139

Manufacturer Part Number
AN1139
Description
L6254 - L6268 - L6269 12V DISK DRIVE POWER COMBO IC
Manufacturer
STMicroelectronics
Datasheet
AN1139 APPLICATION NOTE
4.0 SPINDLE CIRCUITS
4.1
The spindle driver has the ability to stand alone start-up the motor using an internal “align & go” algorithm. Al-
though the internal Start-Up will spin-up the motor consistently, the possibility exist where certain applications
might require complete microprocessor control. In this case, the chip provides all the function and signals to ex-
ternally build a custom Start-Up.
4.1.1 Internal Start-Up
The Internal Start-Up is asserted by setting (=1) the START_UP bit (Reg#2.1). Assuming that the motor is sta-
tionary, when RUN and SPIN_EN bits (Reg#2.3.4) are set (=1), after a resynchronization time, the motor will be
in Align mode with Phase 1 active (output A high and output B low. Please note that this output configuration is
true at Power on condition or whenever reset sequencer is asserted, by toggling the R_SEQ bit (Reg#2.2), oth-
erwise can be different). After a Ta time (align time) the sequencer double increments the outputs to Phase 3
(output B high and output C low). After a Ti time (increment time) the sequencer double increments again the
outputs and the controller enters the GO mode, with the sequencer automatically incrementing the output phase
upon detection of the Motor’s Bemf. The times labeled Ta and Ti are two delays that are 25% and 75% respec-
tively of the total delay time and they are determined by the frequency of the system clock signal present on
pin#15, (SYS_CLK). By setting the DOUBLE bit (Reg#9.4), Ta and Ti can be doubled. Ta and Ti are calculated
as formula #2 and #3. The Figure#3 depicts the internal Align & GO auto Start-Up profile.
Figure 3. INTERNAL ALIGN & GO AUTO START-UP PROFILE
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START-UP DESCRIPTION
SEQUENCER
SPIN_EN
OUTPUT
PHASE
ALIGN
RUN
GO
Ta
Ta
Alignament
Tgo
Ti
Go

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