tea1094t NXP Semiconductors, tea1094t Datasheet - Page 10

• Manufacturer Part Number: tea1094t
• Description: Hands Free Ic
• Manufacturer: NXP Semiconductors

Philips Semiconductors
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
Fig.13 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.
1996 Jul 15
handbook, full pagewidth
handbook, full pagewidth
RNOI
Hands free IC
The pin numbers given in parenthesis refer to the TEA1094A.
, the timing can be set. In the basic application of
SIGNAL ENVELOPE
NOISE ENVELOPE
INPUT SIGNAL
from
microphone
amplifier
DUPLEX CONTROLLER
A: 85 dB/ms
B: 0.7 dB/ms
B: 0.7 dB/ms
C: 0.07 dB/ms
TSEN
(24)
LOG
28
R TSEN
C TSEN
C
A
Fig.8 Signal and noise envelope waveforms.
Fig.7 Signal and noise envelope detectors.
TENV
4 mV (RMS)
(23)
27
36 mV
C TENV
to logic
TNOI
36 mV
TNOI
(22)
26
and
C TNOI
10
from
loudspeaker
amplifier
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.8.
B
B
1 mV (RMS)
RSEN
(21)
LOG
25
R RSEN
C RSEN
C
TEA1094; TEA1094A
RENV
A
(20)
24
C RENV
MBG354
to logic
time
B
B
RNOI
Product specification
(19)
23
MGD223
C RNOI