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LC75106V

Digital Echo LSI with Built-in Mic Amplifier

ON Semiconductor 

LC75106V

(4) Mic AMP Gain setting

Mic Amplifier Gain is adjusted according to the resistance value applied to 3pin and 34pin. And low frequency is cut

off by connecting condenser.

Mic Amplifier has built-in ALC (Auto Level Control). Output level can be controlled by inputting the standard

voltage to 31pin.

1

+

−

R1

1) Mic AMP Gain setting

• R1 = 56.2kΩ

[Mic Gain = 38dB]

R2 = R1/Mic Gain

=56.2k/79.4

≈ 680

2) fc setting

R2

ALC

2

VREF

3

4

C2

R2

+

C1

fc =

1

2π R1 C1

(5) ALC control voltage setting

1) ALC control voltage setting

When the ALC detecting voltage is input to 31pin, the ALC operation level can be set.

The setting method becomes as follows.

[VDD = 9.0V/1Vrms setting]

VDD/2 = 9.0/2 = 4.5

1Vrms/2 = √2 * 1 = 1.414V

VALC setting voltage = 4.5 – 1.414 = 3.086V (DC)

ALC setting voltage can be set to put resistance between the terminal VREF and the terminal GND.

* The voltage of the terminal VREF depends on the power-supply voltage and changes.

2) ALC attack time/release time setting

The attack time and the release time of ALC can be set with the capacitor between 2pin - VDD and 35pin - VDD.

capacitor

2.2μF

1.0μF

0.1μF

Attack time

About 60ms

About 35ms

About 16ms

Release time

About 6.0s

About 2.5s

About 0.25s

Note

No. A2153-14/15

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