U4089B Datasheet, PDF (5/25 Pages) ATMEL Corporation – MONOLITHIC INTEGRATED FEATUREPHONE CIRCUIT

U4089B-M
DC Line Interface and
Supply-voltage
Generation
The DC line interface consists of an electronic inductance and an output stage which
charges the capacitor at V_B. The value of the equivalent inductance is given by:
L = R_SENSE ´ C_IND ´ (R_DC ´ R₃₀)/(R_DC + R₃₀)
In order to improve the supply during worst-case operating conditions, the PNP current
source (I_BOPT) supplies an extra amount of current to the supply voltages when the NPN
in parallel is unable to conduct current.
The U4089B-M contains a series regulator which provides a supply voltage V_MP of 3.3 V
at the 2 mA suitable for a microprocessor.
Figure 4. DC Line Interface with Electronic Inductance and Generation of Regulated
and Unregulated Supply
V_L
10 W _SENSE
R_SENSE
C_IND
10 µF
I _BOPT
< 5 mA
+
IND
-
R_DC
R₃₀
30 kW
V _OFFS
V _MP
+
3.3 V
-
3.3 V/
2 mA _{47 µF}
V_B
7V
220 µF
5
4570A–CORD–04/03