Rohm BA6897FP 4-channel btl driver for cd player Datasheet

Optical disc ICs
4-channel BTL driver for CD players
BA6897S / BA6897FP
The BA6897S and BA6897FP are a 4-channel BTL driver for CD player motors and actuators. It has an internal 5V
regulator and standard operational amplifier, and is suited to a wide range of applications.
Applications
CD players, CD-ROM drives
Features
1) Minimal number of external components.
2) Driver gain is adjustable with just one attached resistor.
3) Internal 5V regulator (attached PNP transistor necessary).
4) Internal standard operational amplifier.
5) Internal thermal shutdown circuit.
Absolute maximum ratings (Ta = 25C)
Recommended operating conditions (Ta = 25C)
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Block diagram
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BA6897S/BA6897FP
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BA6897S/BA6897FP
Pin descriptions
BA6897S
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BA6897FP
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BA6897S/BA6897FP
Optical disc ICs
BA6897S/BA6897FP
Input / output circuits
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BA6897S/BA6897FP
Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 8V, f = 1kHz, RL = 8Ω)
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BA6897S/BA6897FP
Measruement circuit (BA6897S)
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Circuit operation
(1) Driver
Inputs to the IC are the focus tracking error signal from
the servo preamplifier and the control signal from the motor.
(2) Regulator
This is a typical series regulator that generates a reference voltage internally. A PNP low saturation transistor
must be connected.
(3) Amplifier
General 4558 type.
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BA6897S/BA6897FP
The input signals, which normally center on 2.5V, are V / I
converted by the preamplifier, generating a current corresponding to the input voltage. This current is passed
through a resistor and into the internal reference voltage
component, the preamplifier output being a signal centering on the internal reference voltage. Two systems
(positive phase and negative phase) are created during
V / I conversion, generating BTL output via the driver buffer.
Optical disc ICs
BA6897S/BA6897FP
Application examples
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BA6897S/BA6897FP
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Operation notes
(1) The BA6897S and BA6897FP have an internal
thermal shutdown circuit. Output current is muted when
the chip temperature exceeds 175C (typically).
(2) If the mute pin voltage is opened or lowered below
0.5V, the output current will be muted. The mute pin
should be pulled up above 2.0V during normal use.
(3) The bias pin is muted when lowered below 1.4V
(typically). Make sure it stays above 1.6V during normal
use.
(4) Muting occurs during thermal shutdown, mute-on
operations or a drop in the bias pin voltage or supply volt-
BA6897S/BA6897FP
age. In each case, only the drivers are muted. During
muting, the output pins remain at the internal bias voltage, roughly (VCC–VF) / 2.
(5) Be sure to connect the IC to a 0.1µF bypass capacitor to the power supply, at the base of the IC.
(6) The radiating fin is connected to the packages internal GND, but should also be connected to an external
ground.
(7) The capacitor between regulator output (pin 6) and
GND also serves to prevent oscillation of the IC, so select
one with good temperature characteristics.
Electrical characteristic curves
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Optical disc ICs
External dimensions (Units: mm)
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BA6897S/BA6897FP
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