TEA1098 Philips Semiconductors, TEA1098 Datasheet - Page 16

• Manufacturer Part Number: TEA1098
• Description: Speech and handsfree IC
• Manufacturer: Philips Semiconductors

Philips Semiconductors
When a dial tone is present on the line, without monitoring,
it would be recognized as noise because it has a constant
amplitude. This would cause the TEA1098 to go into Idle
mode, and the user would hear the dial tone fade away.
To prevent this, a dial tone detector monitors input signals
between pins HFRX and GND. In standard applications,
the detector does not consider a signal level above
25 mV (RMS) to be noise. This level is proportional to the
value of R
input signals between pins TXIN and GNDTX. In standard
applications the detector does not consider a signal level
above 0.75 mV (RMS) to be noise. This level is
proportional to the value of R
1999 Oct 14
handbook, full pagewidth
Speech and handsfree IC
(1) When DLC < 0.2 V, 10 A is forced.
Pin numbers in parenthesis apply to the TEA1098H. Pin numbers not in parenthesis apply to the TEA1098TV.
RSEN
. Similarly, a transmit detector monitors
(7) 11
(3) 7
(2) 6
(5) 9
RNOI
TENV
TNOI
RENV
from logic
ATTENUATOR
from dynamic
TSEN.
limiter
13 mV
13 mV
V dt
Fig.12 Decision logic.
DUPLEX CONTROLLER
16
X
X
X
1
0
Figure 12 shows that the output of the decision logic is a
current source. The logic table shows the relationship
between the input levels and the value of the current
source. The current source can charge or discharge the
capacitor C
current is zero, the voltage on pin SWT becomes equal to
the voltage on pin IDT via the high-ohmic resistor R
(idling). The resulting voltage difference between pins
SWT and IDT can vary between 400 and +400 mV and
determines the TEA1098 mode (see Table 1).
X
X
X
1
0
LOGIC
1
0
0
1
0
(1)
1
X
X
0
X
SWT
10 A
10 A
10 A
at a switch-over current of 10 A. If the
0
0
V ref
MGL345
SWT
IDT
28 (25)
27 (24)
Product specification
R IDT
TEA1098
C SWT
IDT