U4090B-P Datasheet, PDF (8/35 Pages) ATMEL Corporation – Monolithic Integrated Feature Phone Circuit EMI Improved

Figure 3-3. Supply of Functional Blocks Controlled by Input Voltages V_L, V_B, V_RING and by Logic Inputs PD and IMPSEL
VRING
RPC
Voltage
7V
regulator
VB
VMP
VMPS
VL
Power
supply
Voltage
regulator
6.3V
QS
PD
LIDET
RFDO
LIDET
V_LON
RFD
ES _IMPED
CONTR
IMPSEL
TXA
OFFSA
SAI,SA
TXACL
COMP
SACL
AFS
MIC, DTMF
AGA, RA1, RA2
TX MUTE
MUT REC, STBAL
RECATT
The U4090B-P contains two identical series regulators which provide a supply voltage V_MP of
3.3V suitable for a microprocessor. In speech mode, both regulators are active because V_MPS
and V_B are charged simultaneously by the DC-line interface. Output current is 4 mA. The capac-
itor at V_MPS is used to provide the microcomputer with sufficient power during long-line
interruptions. Thus, long flash pulses can be bridged or an LCD display can be turned on for
more than 2 seconds after going on hook. When the system is in ringing mode, V_B is charged by
the on-chip ringing power converter. In this mode only one regulator is used to supply V_MP with a
maximum of 2 mA.
3.1 Supply Structure of the Chip
A major benefit of the chip is that it uses a very flexible supply structure which allows simple real-
ization of numerous applications such as:
• Group listening phone
• Hands-free phone
• Ringing with the built in speaker amplifier
• Answering machine with external supply
The special supply topology for the various functional blocks is illustrated in Figure 3-3.
8 U4090B-P
4741C–CORD–11/05