AN1139 STMicroelectronics, AN1139 Datasheet - Page 34

• Manufacturer Part Number: AN1139
• Description: L6254 - L6268 - L6269 12V DISK DRIVE POWER COMBO IC
• Manufacturer: STMicroelectronics

AN1139 APPLICATION NOTE
as Hex.0 or Dec.0). The zero current is set as VCC/2 (DAC set as Hex.2000 or Dec.8192). The resolution volt-
age (per LSB) is given by the full scale voltage (2V) divided by 14Bit (16384) and it is equal to 122 V.
5.3
The retract profile is set by the “PKV_1”, ”PKV_2“ bits (Reg #9.0.1), for Parking Voltage and ” RT0”, “RT1” bits
for Parking Time (Reg #9.3.6) in the serial port. Because these bits are not reset by PORB, they must be con-
figured through the serial port after power-up. When programming Retract Time, the Reg#8.2 bit must be always
set to 0. Tables #7 and #8 show respectively the Retract Voltage and Retract Time options.
Table 7. VCM Retract Voltage
Table 8. VCM Retract Time
The retract sequence is initiated by a falling edge of PORB or by a “0” to ”1” transition on the ”RETRACT” bit
(Reg #9.7). Figure #16 shows the Vcm Retract and Spindle Brake sequence at power off.
Figure 16. Power Off Sequence
34/64
PKV_1
VCC
RETRACT
0
0
1
1
RT0
POWER ON
0
0
1
1
PKV_2
12V
0
1
0
1
POR
L6254 Retract Voltage
Retract Time
Reg#9.3.6
Rectification
Retract Voltage
RETRACT
RT1
0.725V
0.531V
1.300V
1.080V
Bemf
Reg#9.0.1
0
1
0
1
on pin#12 (BRK_CAP)
Brake Time
Capacitor
BRAKE
L6268/L6269 Retract Voltage
Retract Time
320ms
640ms
160ms
320ms
0.850V
0.650V
1.600V
1.150V
Time