U4089B-P_05 Datasheet, PDF (5/26 Pages) ATMEL Corporation – Monolithic Integrated Feature Phone Circuit

U4089B-P
3. 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-P contains a series regulator which provides a supply voltage V_MP of 3.3V at 2 mA
suitable for a microprocessor.
Figure 3-1. DC Line Interface With Electronic Inductance and Generation of Regulated
and Unregulated Supply
V_L
10
SENSE
R_SENSE
C_IND
10 µF
I _BOPT
< 5 mA
+
IND
-
R_DC
R₃₀
30 kΩ
V _OFFS
V _MP
+
3.3V
-
3.3V/
2 mA _{47 µF}
V_B
7V
220 µF
Figure 3-2. Functional Blocks for Power Supply
V_L
Power
supply
Voltage
regulator
V_B
7V
V _MP
4518C–CORD–10/05
LIDET
V _LON
ES _IMPED
CONTR
IMPSEL
TXA
TXACL
OFFSA
COMP
SAL, SA
SACL
AFS
MIC, DTMF
AGA, RA
TX MUTE
MUT REC, STBAL
RECATT
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