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2000 Mar 21
10
Philips Semiconductors
Preliminary specification
Speech and handsfree IC
TEA1098A
Fig.6 Current consumption on V
DD
.
handbook, full pagewidth
IDD (A)
1.0
1.5
2.5
3.0
VDD (V)
2.0
10.0u
100.0n
10.0n
1.0u
10.0p
1.0n
100.0p
MGL438
S
UPPLY FOR MICROPHONE
(
PINS
MICS
AND
GNDTX)
The MICS output can be used as a supply for an electret
microphone. Its voltage is equal to 2.0 V; it can source a
current up to 1 mA and has an output impedance equal to
200
.
L
OW VOLTAGE BEHAVIOUR
For line currents below 9 mA, the reference voltage is
automatically adjusted to a lower value; the V
BB
voltage
follows the SLPE voltage with 250 mV difference. The
excess current available for other purposes than DC
biasing of the IC becomes small. In this low voltage area,
the IC has limited performances.
When the V
BB
voltage becomes lower than 2.7 V, the V
BB
detector of the receive dynamic limiter on pin LSAO acts
continuously, discharging the capacitor connected to
pin DLC. In the DC condition, the loudspeaker is then
automatically disabled below this voltage.
When V
BB
goes below 2.5 V, the TEA1098A is forced into
a low voltage mode whatever the levels on the logic inputs
are. It is a speech mode with reduced performances only
enabling the microphone channel (between the MIC inputs
and LN) and the earpiece amplifier. These two channels
are able to deliver signals for line currents as small as
3 mA. The HFC input is tied to GND sinking a current
typically equal to 300
μ
A.
P
OWER
-
DOWN MODE
(
PIN
PD)
To reduce consumption during dialling or register recall
(flash),theTEA1098Aisprovidedwithapower-downinput
(PD). When the voltage on pin PD is LOW, the current
consumption from V
BB
and V
DD
is reduced to 460
μ
A
typically. Therefore a capacitor of 470
μ
F on V
BB
is
sufficient to power the TEA1098A during pulse dialling or
flash. The PD input has a pull-up structure. In this mode,
the capacitor C
REG
is internally disconnected.