U4090B Datasheet, PDF (9/34 Pages) TEMIC Semiconductors – Monolithic Integrated Feature Phone Circuit

U4090B
The U4090B contains two identical series regulators,
which provide a supply voltage V_MP of 3.3 V 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
capacitor at V_MPS is used to provide the microcomputer
with sufficient power during long line interruptions. Thus
long flash pulses can be bridged or a 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 max. 2 mA.
Supply structure of the chip
As a major benefit the chip uses a very flexible system
structure, which allows simple realization of numerous
applications such as:
group listening phone
handsfree 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 6.
VRING
VL
RPC
Power
supply
Voltage
regulator
Voltage
regulator
7V
6.3 V
VB
VMP
VMPS
QS
PD
LIDET
LIDET
VLon
ES _IMPED
CONTR
IMPSEL
RFDO
RFD
TXA
TXACL
OFFSA
COMP
SAI,SA
SACL
AFS
MIC, DTMF
AGA, RA1, RA2
TX MUTE
MUT REC, STBAL
RECATT
94 8046
Figure 6. Supply of functional blocks is controlled by input voltages V_L, V_B, V_ring
and by logic inputs PD and IMPSEL
There are four major supply states:
1. Speech condition
2. Power down (pulse dialing)
3. Ringing
4. External supply
For line voltages below 1.9 V the switches remain in their
quiescent state as shown the diagram.
OFFSACOMP disables the group listening feature (SAI,
SA, SACL, AFS) below line currents of approximately
10 mA.
1. In speech condition the system is supplied by the line
current. If the LIDET-block detects a line voltage
above the fixed threshold (1.9 V), the internal signal
VLON is activated, thus switching off RFD and RPC
and switching on all other blocks of the chip.
2. When the chip is put into Power-down mode
(PD = high), e.g. during pulse dialing, the internal
switch QS shorts the line and all amplifiers are
switched off. In this condition LIDET, voltage
regulators and IMPED CONTR are the only active
blocks.
TELEFUNKEN Semiconductors
9 (34)
Rev. C1, 28-Oct-96
Preliminary Information