TELEFUNKEN Semiconductors
U3810BM
Rev. A1: 19.01.1996
1 (31)
Multi Standard Feature Phone Integrated Circuit
Description
The U3810BM multi-standard feature phone circuit is
designed to be used with a microcontroller using a 2-wire
serial bus. It performs all speech and line interface
functions required in an electronic telephone set: the
ringing function with switching regulator and melody
generator, the DTMF dialling, the loudhearing with
antilarsen and antidistortion systems, a power supply, a
clock and a reset for the microcontroller. Transmit, receive
and loudhearing gains control / AGC range / DTMF
frequencies, pre-emphasis and level / melody generator,
and mutes are programmable through the serial bus.
Block diagramm
Speech
circuit
Tone
ringer
LH
DTMF
dialer
MC
with
EEPROM
93 7600 e
Serial bus
Loudhearing
and
Tone ringing
Figure 1
Applications
D Feature phones
D Answering machines
D Fax machines
Benefits
D Complete system integration of analog signal
processing and digital control circuitry
D One IC for various PTT standards, e.g. programmable
specification via
mC
D Only three low-cost transducers needed (instead of
four)
TELEFUNKEN Semiconductors
U3810BM
Rev. A1: 19.01.1996
2 (31)
Features
D Slope of DC characteristics adjustable by an external
resistor
D Gain of transmit and receive amplifiers automatically
adjusted by line length control
D Regulation range adjustable by the serial bus
D Possibility of fixed gain (PABX)
D Sidetone balancing system adjustable with line length
or by the serial bus
D Dynamic impedance adjustable by external
components
D Stabilized power supply for peripherals
D Confidence level during dialling
D +6 dB possibility on second stage transmit gain
D Transmit and receive gains adjustable by serial bus
D Extra transmit input for handsfree and answering
machine purpose
D +6 dB possibility on receive gain
D Receive amplifier for dynamic or piezo-electric
earpieces
D Extra receive output for handsfree purpose
D High impedance microphone inputs suitable for
dynamic, magnetic, piezo-electric or electret
microphone
D Distortion of line signal and sidetone prevented by
dynamic range limitation in transmission
(anti-clipping)
D Squelch system in transmission prevents "room noise"
are being transmitted, and improves anti-larsen
efficiency (can be inhibited).
D Loudhearing gain programmable in eight steps of 4 dB,
using the serial bus, or linearly adjusted, using a
potentiometer
D Anti-larsen system efficiency is increased when
inhibiting squelch
D Loudhearing anti-distortion system by automatic gain
control versus available current and voltage
D Switching regulator in ringing phase
D Input ringing detection, threshold and impedance
adjustable with external resistors
D Ringing zero crossing information for external
microprocessor
D Ringing programmable gain in eight steps of 4 dB using
the serial bus
D Melody generator, with 30 frequencies in steps of semi
tones, driven by serial bus
D Internal speed-up circuit permits a faster charge of
VDD and VCC capacitor
D DTMF dialer driven by serial bus, in particular level
and pre-emphasis adjustment
D Ability to transmit a confidence tone in speech mode
using melody generator frequencies
D Five independent mutes driven by serial bus (two in
transmission, two in reception, one for the transmit /
receive loop)
D Standard low-cost ceramic 455 kHz / clock output for
the microcontroller
D Extra loudhearing input for answering machines,
handsfree and base station of phones cordless with
loudhearing
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