TEA1099H 데이터 시트보기 (PDF) - Philips Electronics

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TEA1099H

Speech and handsfree IC with auxiliary inputs/outputs and analog multiplexer

Philips Electronics 

Philips Semiconductors

Speech and handsfree IC with auxiliary

inputs/outputs and analog multiplexer

Product specification

TEA1099H

The buffer amplifiers which apply the compressed signals

to TENV and RENV have a maximum source current of

120 µA and a maximum sink current of 1 µA. Together with

the capacitor CTENV and CRENV, the timing of the signal

envelope monitors can be set. In the basic application, the

value of both capacitors is 470 nF. Because of the

logarithmic compression, each 6 dB signal increase

means 18 mV increase of the voltage on the envelopes

TENV or RENV at room temperature. Thus, timings can be

expressed in dB/ms. At room temperature, the 120 µA

sourced current corresponds to a maximum rise-slope of

the signal envelope of 85 dB/ms. This is sufficient to track

normal speech signals. The 1 µA current sunk by TENV or

RENV corresponds to a maximum fall-slope of 0.7 dB/ms.

This is sufficient for a smooth envelope and also eliminates

the effect of echoes on switching behaviour.

To determine the noise level, the signals on TENV and

RENV are buffered to TNOI and RNOI. These buffers have

a maximum source current of 1 µA and a maximum sink

current of 120 µA. Together with the capacitors CTNOI and

CRNOI, the timings can be set. In the basic application

(see Fig.16) the value of both capacitors is 4.7 µF. At room

temperature, the 1 µA sourced current corresponds to a

maximum rise-slope of the noise envelope of

approximately 0.07 dB/ms.

This is small enough to track background noise and not to

be influenced by speech bursts. The 120 µA current that is

sunk corresponds to a maximum fall-slope of

approximately 8.5 dB/ms. However, during the decrease

of the signal envelope, the noise envelope tracks the

signal envelope so it will never fall faster than

approximately 0.7 dB/ms. The behaviour of the signal

envelope and noise envelope monitors is illustrated in

Fig.10.

handbook, full pagewidth

DUPLEX CONTROLLER

from

microphone

amplifier

LOG

to logic

from

loudspeaker

amplifier

LOG

to logic

TSEN

4

TENV

3

TNOI

2

RTSEN

CTSEN

CTENV

CTNOI

RSEN

6

RENV

7

RNOI

5

RRSEN

CRSEN

CRENV

CRNOI

MGM302

Fig.9 Signal and noise envelope detectors.

1999 Apr 08

15

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