Datasheet BH3852S, BH3852FS Datasheet (ROHM)

Audio ICs

Sound control IC

BH3852S / BH3852FS

The BH3852S and BH3852FS are signal processing ICs designed for volume and tone control in CD radio cassettes
and other audio products. They can be used without a microcomputer because they use DC current for control.

Applications
CD radio cassettes, micro components, car stereos, tele­visions

Features

1) Can control volume (main volume) and tone (bass,
treble).

2) Volume is produced by a low-distortion, low-noise
VCA, is controlled with DC current, and, due to an in­ternal reference voltage with temperature com­pensation, can control two channels with a single
variable resistor.

3) Input amp can be used for gain adjustment, and ma­trix surround yields powerful sound.

Absolute maximum ratings (Ta = 25C)

Recommended operating conditions

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Audio ICs BH3852S / BH3852FS

Block diagram

Pin descriptions

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Audio ICs BH3852S / BH3852FS

Input / output circuits

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Audio ICs BH3852S / BH3852FS

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Audio ICs BH3852S / BH3852FS

Electrical characteristics(unless otherwise noted, Ta = 25C, VCC = 8V, f = 1kHz, BW = 20  20kHz,

VOL = Max., TONE = ALL FLAT, R

g = 600Ω, RL = 10kΩ, INPUT_AMP_GAIN = 0dB)

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Audio ICs BH3852S / BH3852FS

Measurement circuit

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Audio ICs BH3852S / BH3852FS

Application example

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Audio ICs BH3852S / BH3852FS

FOperation notes
(1) Operating power supply voltage range
As long as the operating power supply voltage range and
ambient temperature are kept within the specified range,
the basic circuits are guaranteed to function, but be sure
to check the constants as well as the element settings,
voltage settings, and temperature settings. Also, volume
curves sometimes depart from target values when there
is a combination of low temperature and reduced power.

(2) Primary amp

S The input impedance is 47kΩ.
S A buffer if R and C
S The gain can be set by R and the 20kΩ.

G

VC = (R + 20kΩ)/R

Note: Set C

2 (input coupling) and C1 (used to set the

gain) depending on the frequency band used.

1 are not present.

(3) Bass filter

S The BPF is composed of a multifeedback active filter.

o can be varied according to the value of C.

f
(theoretical equation)

1

O = Q (C1)C2)

f

2π
R2

G = 1)

5kΩ

(When R

O = Q = 1.36 G = 8.5

f

1 = 11.5kΩ, R2 = 85kΩ, C1 = C2 = C)

5.1 10
C

*

6

1R2C1C2

R

1

C
C2

1
2

R1

R2C1C2

*

1

1

Note: Filter gain is calculated using the equation on the left. Total output gain is the

sum of the gain for each of the internal circuits.

1
2

*

1

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Audio ICs BH3852S / BH3852FS

(4) Treble filter

S Cutoff frequency (f

changed using the attached C

f

C1 =

C1 for the recommended constant is

The f

C1) for the bypass filter can be

3.

1

3 2kΩ

2π C

approximately 8 kHz.

C2 is determined by the band of the built-in amp.

S f

f

C2 is approximately 100 kHz.

Tone control is designed to yield a variation of
±15dB (Typ.) when the frequency to be boosted or
cut is at the peak or bottom of the filter frequency
characteristic, so please take the frequency charac­teristic into consideration in designing the filter.

(5) Signal level setting
The following figure represents the standard setting for
the BH3852FS / BH3852S.

LAs indicated above, if the front volume and rear volume
input level are set so as not to exceed +6dBV (2Vrms),
the pre-amp gain setting can be used to improve the S/N
ratio.

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Audio ICs BH3852S / BH3852FS

(6) Matrix surround

The structure of the matrix surround is as shown in the
figure above. Use the equations shown in the figure to
calculate gain.

(7) DC control
It is recommended that DC control of the VC, TC, BC, and
SC pins be performed by voltage delivered in variable
volume from the V

ref pin (12th pin). When using variable

volume, take the discharge current of each pin into ac­count in determining its settings.
Note:The voltage range for DC control is 0 (V) to V
Be sure not to apply voltage greater than V

ref (V).

ref (V) to any

pin.
(8) GND

If several capacitors with good high-frequency charac­teristics are connected in parallel to the 12th-pin capaci­tor, the characteristics will be improved with respect to
static electricity noise. (Recommended : ceramic capaci­tors of 0.001µF to 0.1µF)

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Audio ICs BH3852S / BH3852FS

Electrical characteristic curves

External dimensions (Units: mm)

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