Technical Note

3/9

www.rohm.com

2010.06 - Rev.A

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BH7881EFV

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Block diagram

Fig.1

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Control pin descriptions

1. ACTIVE/SUSPEND:2PIN

Control input

Mode

Function

H

SUSPEND

Suspended state (Except REG)

L

ACTIVE

Active state

When suspended, the regulator (REG) is in an active state and the SP/HP/LINE amplifier is in a suspended state. Originally,

signals from input resistance and feedback resistance leaked into the speaker output even when suspended, because of

the series connection of an inverting amplifier. However, since the signals are cut off on their way in this IC, signal leaks do

not occur in speaker output. (Signals due to feedback resistance are output in LINE amplifier output.)

2. POWER LEVEL:8PIN

Control input

Mode

Function

H

Limiter H

3Vf peak limiter ON (Output approx. 1.25 W)

OPEN

Limiter L

2Vf peak limiter ON(Output approx .0.70W)

L

Limiter OFF

limiter OFF

*VCC=5V,RL=4ohm,VIN=-8dBV

Since a limiter uses diode characteristics, it has temperature characteristics. On the high temperature side, amplitude tends

to decrease, which is a characteristic that protects the IC. Since setting in speaker mode is assumed, it is ineffective (limiter

OFF) in headphone mode. Moreover, precautions must be taken when input is so great, that output becomes a square

wave, since this could cause local oscillation.

3. BASSBOOST ON/OFF:11PIN

Control input

Mode

Function

H

ON

BASSBOOST:ON

L

OFF

BASSBOOST:OFF

The capacitor that constitutes BASSBOOST is eliminated, and also functions as a gain switch.

4. SP/HP:12PIN

Control input

Mode

Function

H

SP+HP

SP:ON, HP:ON

L

HP

SP:OFF,HP:ON

By using the headphone mode in a speaker MUTE mode, it is possible to completely cut off the pop noise when switching

when VCC ON or OFF, or to ACTV or SPND. For control sequence and other information, see the following pages.

*Not all control pins have pull up or pull internal resistors. Therefore add pull up or pull down resistors, accordingly (PIN8 is an exception.)