Datasheet BA6897S, BA6897FP Datasheet (ROHM)

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).

Absolute maximum ratings (Ta = 25C)

4) Internal standard operational amplifier.

5) Internal thermal shutdown circuit.

Recommended operating conditions (Ta = 25C)

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Optical disc ICs BA6897S/BA6897FP

Block diagram

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Optical disc ICs BA6897S/BA6897FP

Pin descriptions
BA6897S

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Optical disc ICs BA6897S/BA6897FP

BA6897FP

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Optical disc ICs BA6897S/BA6897FP

Input/output circuits

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Optical disc ICs BA6897S/BA6897FP

Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 8V, f = 1kHz, RL = 8Ω)

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Optical disc ICs BA6897S/BA6897FP

Measruement circuit (BA6897S)

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Optical disc ICs BA6897S/BA6897FP

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.

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.

(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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Optical disc ICs BA6897S/BA6897FP

Application examples

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Optical disc ICs BA6897S/BA6897FP

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Optical disc ICs BA6897S/BA6897FP

Operation notes
(1) The BA6897S and BA6897FP have an internal
thermal shutdown circuit. Output current is muted when
the chip temperature exceeds 175C (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-

Electrical characteristic curves

age. In each case, only the drivers are muted. During
muting, the output pins remain at the internal bias volt­age, roughly (V
(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.

CC–VF)/2.

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Optical disc ICs BA6897S/BA6897FP

External dimensions (Units: mm)

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