146
Optical disc ICs
Headphone amplifier with
internal LPF and EVR for CD-ROM
BH3540AFS
The BH3540AFS is an H / P amplifier with internal secondary LPF and EVR circuits. When multibit output from a
D / A converter is input, the secondary LPF outputs an audio signal. Output level for headphones can be changed with
the EVR circuit. This IC also has independent internal mute circuits for the left and right channels.
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Applications
CD-ROM drives and other products (with line and headphone output pins) that process digital audio signals
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Features
1) Internal LPF, line amplifier and EVR.
2) Internal mute function.
3) Internal thermal shutdown circuit.
4) No attached oscillation prevention components are
needed, even at a load of 8
.
5) Mute function reduces the popping noises that can
occur when the power is turned on and off.
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Block diagram
147
Optical disc ICs
BH3540AFS
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Absolute maximum ratings (Ta = 25
_
C)
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Recommended operating conditions
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Electrical characteristics (unless otherwise noted, Ta = 25
_
C, V
CC
= 5.0V, line R
L1
= 50k
, H / P R
L2
= 32
,
V
IN
= 1.8dBV, f = 1kHz, EVR = Max.)
150
Optical disc ICs
BH3540AFS
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Operation notes
(1)
Preventing popping noises
The BH3540AFS has a mute function that reduces the
popping noises that can occur when the power is turned
on or off. To further reduce these popping noises, attach
a capacitor and resistor to the mute pin (pins 3 and 14).
(2)
Recommended time chart
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Electrical characteristic curves
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External dimensions (Units: mm)
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