AK2510 查看數據表（PDF） - Asahi Kasei Microdevices

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AK2510

Voice Switch LSI for Hands-Free Phone

Asahi Kasei Microdevices 

ASAHI KASEI

VOICE SWITCH CORE BLOCK DIAGRAM

[AK2510]

Noise

Level

Detector

Noise

Level

Detector

Rx Attenuator

Attenuator Control

Tx Attenuator

• Block Descriptions

BLOCK

Attenuator Control

Rx Attenuator

Tx Attenuator

Noise Level Detector

Function

This circuit automatically controls the gain of the transmit and receive

attenuators based on the signal comes from the path and NLD (Noise Level

Detector).

When one is at 0dB gain, the other is at minimum attenuation. Both

attenuators are controlled by a single output from the Attenuator Control

which ensure the sum of their gain will remain constant at a typical value.

The purpose of the noise level detector is to distinguish speech from

background noise. This block monitors the average value of the back ground

noise power and this information is used for the Attenuation Control in order

to be able to operate the voice switch function under the noisy conversation

circumstances. The NLD is also response to the receive signal attenuate

caused by the line loss.

• Timing of the Rx and Tx Attenuator

TX_Voice_Activity

RX_Voice_Activity

0dB

TX_ATT _gain

Minimum Gain

0dB

RX_ATT_gain

Minimum Gain

This diagram shows the basic operation of the AK2510 voice switch functions. When the voice come to

the transmit path, the Attenuator Control sets the Tx Attenuator to 0dB gain and Rx Attenuator to the

minimum gain. When the voice come from the receive path, the Attenuator Control sets the Rx

Attenuator to 0dB gain and Tx Attenuator to the minimum gain. When there is no voice in either path,

the AK2510 transit to the “watch status” and the attenuator’s gain of each path stays at nearly half

positions. Minimum gain and the attenuator’s gains in the watch status can be changed by the internal

register via serial CPU interface. During the Attenuator transition, the Attenuator Control prevents the

AK2510 from “singing” and “motorboating” caused by the echo.

AKM

-2-

AK2510-E-00

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