L6256 Datasheet, PDF (1/28 Pages) STMicroelectronics – 12V COMBO

L6256
12V COMBO
DESCRIPTION
The 12 Volt Combo chip is a combination spindle
motor driver, voice coil driver and D/A converter.
The part can be used in,application like HDD.
The VCM amplifiers drive a low impedance coil
and are set up to accept RC compensation, which
allows a wide bandwidth with absolute minimum
phase lag. The sense resistor/amplifier arrange-
ment allows full current loop operation. The loop
gain is changeable by attenuating the VCM DAC
voltage amplitude in cascadable stages.
The Spindle driver is a PWM only voltage loop
with power supply feedforward, driving a 3 phase
sensorless brushless DC motor. Since it uses
PWM operation at full run speed, it has output
slew rate control during start and run modes.
There is an inductive clamp circuit to limit flyback
voltage transients across the supply voltage dur-
ing motor phase changes and during the braking
sequence. Only the 2 phase or bipolar commuta-
tion pattern is produced by the internal commuta-
tion circuitry. A commutation register allows arbi-
Figure 1. Block Diagram
PLCC44
ORDERING NUMBER: L6256
trary winding sequencing during certain opera-
tions. Internal protection against crossover
spikes is built in.
3 phase or tripolar commutation can be supported
in software during start by writing a commutation
pattern directly to the preload register.
Tripolar operation requires that more than two
phase drivers contribute current simultaneously.
The current limit circuitry reflects this and allows
33% higher current limit, which produces nearly
18
CP_OUT
19
CP_CAP
33
H_VPWR
34
VDD
15
VCC
10
nPOR
9
POR_RC
27
PARK
13
SCLK
14
SDIO
28
CSELB
BYPASSC 16
CHARGE
PUMP
DAC
32
IO_VC
31
I_VC
26
A_IN
30
A_OUT B_OUT
25 23
VCM CLASS AB
DRIVERS
VPWR
2
UV
DETECT
POR
10 BIT
DAC
VCM
COMMAND
CHANNEL
VCM CONTROL
VCM
RETRACT
h_vpwr
VCM
LOGIC
THERMAL
-
+
A
AMP
PWR GND
-
+
h_vpwr
B
AMP
CLK
SYNC
SERIAL INTERFACE
3
BANDGAP
VOLTAGE
REFERENCE
CURRENT
SOURCES
SPINDLE LOGIC
SPINDLE SEQUENCER
BRAKE
DELAY
COUNTER
DYNAMIC
CLAMPING
SPINDLE DRIVERS
ANALOG
24
TEST MUX
SYNC
CLAMP
3
20
QDRIVE
21
VREG_IN
22
CUR_IN
3.3V LINEAR
REGULATOR
6,7,17,29,39,40
FEEDFORWARD
COMPENSATION
upper
lower
PRE-DRIVERS
8
11
R_ PWM_
SLEW IN
36
37
5
PWM_ FF_ SP_
DC COMP CLK
BEMF SENSING
ZERO CROSSING
DETECTION
CURRENT
LIMIT
SENSING
38 12
35
SH_ BEMF_ REF_
OUT DET
IN
44
SP_
G2
4
SP_
G1
24
VC_PWR
2
SP_P1
42
SP_P2
43
SP_A
1
SP_B
3
SP_C
41
C_TAP
D97IN571
December 1997
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