U4091BM-R Datasheet, PDF (6/38 Pages) ATMEL Corporation – Programmable Telephone Audio Processor

Table 2-1. Pin Description
Pin
Symbol Function
40
AMPB Input for playback signal of answering machine
41
AMREC Output for recording signal of answering machine
42
STO
Output for connecting the sidetone network
43
STC
Input for sidetone network
44
STRC Input for sidetone network
Note: 1. The protection device at pin RECIN is disconnected.
3. DC Line Interface and Supply-voltage Generation
The DC line interface consists of an electronic inductance and a dual-port output stage which
charges the capacitors at VMPS and VB. The value of the equivalent inductance is given by:
L = -²----^×------^R-----^S---^E---^N---^S---^E-----^×------^C----^I--^N---^D-----^×------⁽--^R-----^D---^C-----^×------^R----³---⁰---⁾
(R_DC + R₃₀)
The U4091BM-R contains two identical series regulators which provide a supply voltage VMP of
3.3V suitable for a microprocessor. In speech mode, both regulators are active because VMPS
and VB are charged simultaneously by the DC line interface. The output current is 6 mA. The
capacitor at VMPS 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, VB is charged by
the on-chip ringing power converter. In this mode, only one regulator is used to supply VMP with
maximum 3 mA.
4. Supply Structure of the Chip
A main benefit of the U4091BM is the easy implementation of various applications due to the
flexible system structure of the chip.
Possible applications:
• Group listening phone
• Hands-free phone
• Phones which feature ringing with the built-in speaker amplifier
• Answering machine with external supply
The special supply topology for the various functional blocks is shown in Figure 4-1 on page 7.
There are four major supply states:
1. Speech condition
In speech condition, the system is supplied by the line current. If the LIDET block
detects a line voltage above approximately 2V, the internal signal VLON is activated.
This is detected via the serial bus, all the blocks which are needed have to be switched
on via the serial bus.
For line voltages below 2V, the switches remain in quiescent state as shown in the
diagram.
6 U4091BM-R
4872A–CORD–08/05