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PDF LB8108M Data sheet ( Hoja de datos )
| Número de pieza | LB8108M | |
| Descripción | Actuator Driver for Portable CD Players | |
| Fabricantes | Sanyo | |
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Ordering number : EN4946A
Monolithic Digital IC
LB8108M
Actuator Driver for Portable CD Players
Applications
The LB8108M is an actuator driver for use in portable CD
players that operate at a power supply voltage of 2.4 (two
nicad batteries) or 3.0 V (two dry-cell batteries).
Functions and Features
• Includes four H bridge driver channels to drive the four
CD player actuators (focus coil, tracking coil, spindle
motor and sled motor).
(output dynamic range: maximum of about 2 V)
• Includes a 3.9 V (typical) step-up circuit to supply the
DSP, ASP and microprocessor used in the CD player.
Also includes another voltage step-up circuit whose
voltage can be set with external resistors.
(However, note that the transistors, inductors, capacitors
and diodes required for drive operation are all external
components.)
• Built-in oscillator circuit for these converters
(external resistor and capacitor required)
• Detects the maximum value of the four driver outputs
and supplies a voltage slightly higher than that voltage
to the H bridge block in each of the four channels using
PWM voltage converter. This allows a drive scheme
with extremely low loss to be implemented.
(However, note that the pnp transistor, inductor,
capacitor, and diodes for the PWM circuit are all
external components.)
• Built-in laser diode drive and APC circuits
(IOmax ≈ 100 mA. This function can be turned off by a
control voltage input. It is composed of step-up
converter and series regulator.
However, note that the transistors, inductors, capacitors
and diodes required for drive operation are all external
components.)
• The sled motor drive circuit operates in 2 modes, that
are normal V-type drive mode and step drive mode
which is highly effective in reducing power dissipation.
• A step-down converter that convert external input
voltage that exceed 5 V into 3.5 V VCC operates when
an external voltage input is applied. This simplifies
power supply design and thermal design for applying
VCC.
(This circuit turns on at the same time an external
voltage is applied and generates a 3.5 V VCC, which is
utilize for nicad battery charging.)
• Built-in microprocessor reset circuit (external capacitor
required)
(This circuit detects the VCD pin voltage and operates a
reset voltage with an H-side of 2.2 V (typical) and an L-
side of 2.1 V (typical).)
• Two built-in battery check comparator channels
• System start and stop under microprocessor control
• Actuator muting function included.
(all four channels at the same time)
• Built-in thermal shutdown circuit
Package Dimension
unit: mm
3148-QFP44MA
[LB8108M]
SANYO: QIP44MA
SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters
TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN
73196RM/51795TH (OT) No. 4946-1/12
1 page  
Pin Functions
Pin No.
Symbol
1, 44
33, 34
2
IN1, IN2
IN3, IN4
ASPREF
43, 42
41, 40
38, 37
36, 35
OUT1+, 1–
OUT2+, 2–
OUT3+, 3–
OUT4+, 4–
3, 31
VOUT
4 VCD
5 MUTE
6 SLREF
7 SLM
8 LD GND
LB8108M
Equivalent circuit
Function
The actuator control signals corresponding to
IN1: focus, IN2: tracking, IN3: spindle, IN4:
sled. Input from the ASP (DSP).
Focus coil actuator drive output
Tracking coil actuator drive output
Spindle motor drive output
Sled motor drive output
(Each channel includes built-in spark killer
diodes.)
Power supply for the four H bridge driver
channels. An external PWM step-up circuit
can be used to generate a voltage slightly
higher than the maximum voltage output by
any of the four output channels.
Input for the 3.9 V step-up circuit. The drive
control system operates on this voltage. This
voltage can also be supplied to other ICs in
the system, such as the DSP and the
microprocessor.
Input for muting of the four actuator channels
at the same time.
High: mute applied.
Threshold input used when operating the
sled motor in step drive mode.
Input that selects sled motor step drive
mode.
High: V-type selected
Low: Step mode
Dedicated ground connection for the internal
reference voltage for laser diode APC
control.
Connect to a ground near the laser diode.
Continued on next page.
No. 4946-5/12
5 Page 
LB8108M
First, when VCC is adequately high (about 2.5 V or over) the laser diode is driven by the system consisting of VCC, an
inductor and a Schottky diode without driving LDUPB. Then, when VCC falls and VLD – VLDO become under about 0.3
V, LDUPB is driven, VLD is stepped up, and the circuit is controlled so that VLD – VLDO is held at 0.3 V (typical).
The following describes the laser diode intensity adjustment function supported by the LB8108M.
First, set up the pickup so that the monitor diode output is about 0.2 V in the normal usage range.
When LDCTL is in the range 0.0 to 0.5 V the LD drive function will be in the cutoff state and the laser diode will not be
driven. As the LDCTL voltage rises, the LD drive reference voltage shown in the figure varies between 0.1 and 0.3 V.
Then, the VLDO pin voltage is controlled so that the monitor diode output and that reference voltage become identical.
However, since the output current peak is 100 mA (typical), the output voltage will not increase when an output current
in excess of that value is required.
(Since the intensity adjustment will go to its maximum setting when the LDCTL pin is open, an appropriate voltage must
be applied to the LDCTL pin.)
Sled Control
The figure below shows the operation of the LB8108M’s sled actuator step control.
When the SLM pin is set high, the LB8108M operates in the normal V-type control mode. However, the LB8108M can
be set to operate in a sled drive mode that is highly efficient at
reducing power dissipation by setting the SLM pin low.
The step drive start level is input from the SLREF pin. (Only a
voltage higher than VASPREF will be accepted.)
The circuit operates once in step drive mode following the locus
of line in the figure. Then, on returning, it operates in V-type
control following the locus of line .
Next, the circuit can be operated in step mode by putting the
input (VIN4) into the reverse region.
(If the input does not enter the reverse region, the circuit will
continue to operate in V-type mode.)
No. 4946-11/12
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LB8108M.PDF ] | |
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