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322

Optical disc ICs

BA6297AFP

FCircuit operation

The BA6297AFP comprises a 4-channel driver, internal

bias amplifier, mute pin and thermal shutdown.

(1)

Driver

The driver uses a buffer to output one of the outputs from

its preamplifier with no modification, and uses an inver-

sion amplifier to invert the other output before sending it

to the driver buffer. The inversion amplifier’s reference is

the bias voltage generated internally (pin 7 voltage), and

so the preamplifier output must make the zero level equal

to the internal bias voltage. See Figs. 7 and 8 for exam-

ples.

(2)

Internal bias amplifier

Configured as shown in Fig. 9. The internal bias voltage

(3)

Mute pin (pin 15)

The output current is muted when this pin receives the

low level or a high impedance. Set the pin voltage at high

during normal operation.

(4)

Thermal shutdown

The BA6297AFP has an internal thermal shutdown cir-

cuit. Output current is muted when the chip temperature

exceeds 175

_C (typically).