tea1099h NXP Semiconductors, tea1099h Datasheet - Page 15

• Manufacturer Part Number: tea1099h
• Description: Speech And Handsfree Ic With Auxiliary Inputs/outputs And Analog Multiplexer
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The buffer amplifiers which apply the compressed signals
to TENV and RENV have a maximum source current of
120 A and a maximum sink current of 1 A. Together with
the capacitor C
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 A
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 A 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.
1999 Apr 08
handbook, full pagewidth
Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer
from
microphone
amplifier
DUPLEX CONTROLLER
TENV
and C
TSEN
LOG
RENV
4
R TSEN
C TSEN
, the timing of the signal
Fig.9 Signal and noise envelope detectors.
TENV
3
C TENV
to logic
TNOI
2
C TNOI
15
from
loudspeaker
amplifier
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 A and a maximum sink
current of 120 A. Together with the capacitors C
C
(see Fig.16) the value of both capacitors is 4.7 F. At room
temperature, the 1 A 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 A 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.
RNOI
, the timings can be set. In the basic application
RSEN
LOG
6
R RSEN
C RSEN
RENV
7
C RENV
to logic
RNOI
Product specification
TEA1099H
5
C RNOI
MGM302
TNOI
and