TEA1098AUH 데이터 시트보기 (PDF) - Philips Electronics

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TEA1098AUH

Speech and handsfree IC

Philips Electronics 

Philips Semiconductors

Speech and handsfree IC

Product specification

TEA1098A

handbook, full pagewidth

DUPLEX CONTROLLER

from

microphone

amplifier

LOG

9

TSEN

RTSEN

CTSEN

to logic

from

loudspeaker

amplifier

LOG

8

TENV

7

TNOI

CTENV

CTNOI

11

RSEN

RRSEN

CRSEN

Fig.9 Signal and noise envelope detectors.

to logic

12

RENV

10

RNOI

CRENV

CRNOI

FCA152

handbook, full pagewidth

INPUT SIGNAL

4 mV (RMS)

1 mV (RMS)

MBG354

SIGNAL ENVELOPE

A

36 mV

B

A: 85 dB/ms

B: 0.7 dB/ms

A

B

NOISE ENVELOPE

C

B: 0.7 dB/ms

C: 0.07 dB/ms

36 mV

B

C

B

time

Fig.10 Signal and noise envelope waveforms.

To determine the noise level, the signals on pins TENV

and RENV are buffered to pins TNOI and RNOI. These

buffers have a maximum source current of 1 µA and a

maximum sink current of 120 µA. Capacitors CTNOI and

CRNOI set the timing. In the basic application, see Fig.17,

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.

2000 Aug 18

14

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