U4089B-MFN ATMEL [ATMEL Corporation], U4089B-MFN Datasheet - Page 5

• Manufacturer Part Number: U4089B-MFN
• Description: MONOLITHIC INTEGRATED FEATUREPHONE CIRCUIT
• Manufacturer: ATMEL [ATMEL Corporation]

DC Line Interface and
Supply-voltage
Generation
4570A–CORD–04/03
The DC line interface consists of an electronic inductance and an output stage which
charges the capacitor at V
L = R
In order to improve the supply during worst-case operating conditions, the PNP current
source (I
in parallel is unable to conduct current.
The U4089B-M contains a series regulator which provides a supply voltage V
at the 2 mA suitable for a microprocessor.
Figure 4. DC Line Interface with Electronic Inductance and Generation of Regulated
V
L
SENSE
10 µF
R
R
BOPT
C
10 W
SENSE
DC
and Unregulated Supply
IND
´ C
) supplies an extra amount of current to the supply voltages when the NPN
IND
SENSE
IND
´ (R
DC
< 5 mA
30 kW
I
R
BOPT
´ R
30
B
V
. The value of the equivalent inductance is given by:
OFFS
+
-
30
)/(R
DC
+ R
30
)
+
-
7 V
3.3 V
V
U4089B-M
V
MP
B
3.3 V/
2 mA
MP
of 3.3 V
47 µF
220 µF
5