TELEFUNKEN Semiconductors
U4091B
Programmable Telephone Audio Processor
Description
The programmable telephone audio processor U4091B is
a linear integrated circuit for use in feature phones, an-
swering machines and fax machines. It contains the
speech circuit, tone ringer interface with dc/dc converter,
sidetone equivalent and ear protection rectifiers. The cir-
cuit is line powered and contains all components
necessary for amplification of signals and adaptation to
the line.
An integrated voice switch with loudspeaker amplifier al-
lows handsfree or loudhearing operation. With an
anti-feedback function, acoustical feedback during loud-
hearing can be reduced significantly. The generated
supply voltage is suitable for a wide range of peripheral
circuits.
Features
D
D
D
D
Speech circuit with anti-clipping
Tone ringer interface with dc / dc converter
Speaker amplifier with anti-distortion
Power supply management, regulated, unregulated
and a special supply for electret microphone
Benefits
D
Savings of one piezo electric transducer
D
Complete system integration of analog signal proces-
sing on one chip
D
Very few external components
D
Voice switch
Applications
Feature phone, answering machine, fax machine, speaker
phone
Voice
switch
Rev. A1: 12.07.1995
Preliminary Information
ÁÁ
ÁÁ
BUS
Speech
circuit
Audio
amplifier
Loudhearing
and
Tone ringing
MC with
EEPROM/
DTMF
Tone
ringer
1 (11)
U4091B
Serial Bus Controlled Functions
Speech circuit
Ringer
TELEFUNKEN Semiconductors
D
Transmit gain: 36 to 52 dB (1 dB step)
D
Receive gain: –7 dB to +9 dB (1 dB step) + one 6 dB
step
D
Volume adjustment
Voice switch
D
Speaker amplifier gain: –10 dB to +30 dB (1.5 dB
step)
D
Mute R, Mute T
D
Automatic gain adjustment ( AGA ): 7 different
D
Impedance selection: 600/ 900
W
characteristics
D
D
D
D
D
D
D
Volume adjustment
Attenuation range: 0 to 50 dB (1 dB steps)
4 thresholds for mode switching
Mute of handsfree microphone
Chip disable
Hand set / handsfree switching
Four point level detection
2 (11)
Preliminary Information
Rev. A1: 12.07.1995
TELEFUNKEN Semiconductors
U4091B
Pin
Symbol
TSACL
SA I
Function
Time constant of anti-clipping of
speaker amplifier
Speaker amplifier input (for
loudspeaker, tone ringer and
handsfree use)
Receive level output 1
Receive level input 1
Handsfree Mic input
Background noise monitor in trans-
mit direction
Receive level input 2
Receive level output 2
Clock
Data
Reset
Internal reference current
generation; RREF = 62 kΩ;
IREF = 20
µA
Side tone reduction output
output resistance is approx. 300
Ω,
maximum load impedance: 10 kΩ.
Reference node for microphone-
earphone and loudspeaker amplifier,
supply for electret microphone
(IM
≤
300
m
A)
Pin Description
Pin
Symbol
DTMF
Function
Input for DTMF signals, also used
for the answering machine and
handsfree input
Output of microphone preamplifier
Non-inverting input of microphone
amplifier
Inverting input of microphone
amplifier
Active high input for reducing the
current consumption of the circuit,
simultaneously V
L
is shorted by an
internal switch
The internal equivalent inductance
of the circuit is proportional to the
value of the capacitor at this pin, a
resistor connected to ground may be
used to reduce the dc line voltage
Line voltage
Reference point for dc- and
ac-output signals
A small resistor (fixed) connected
from this pin to V
L
sets the slope of
the dc characteristic and also effects
the line length equalization
characteristics and the line current
at which the loudspeaker amplifier
is switched on
Unregulated supply voltage for
peripheral circuits (voice switch),
limited to typically 7 V
Output of loudspeaker amplifier
Unregulated supply voltage for
µP,
limited to 6.3 V
Regulated supply voltage 3.3 V for
peripheral circuits (especially
microprocessors), maximum output
current: 2 mA
MICO
MIC 2
MIC 1
PD
RLO1
RLI1
MICHF
BNMT
RLI2
RLO2
C
D
Reset
IREF
IND
V
L
GND
SENSE
STO
V
M
V
B
SAO
V
MPS
V
MP
SWOUT Output for driving external
switching transistor
COSC 40 kHz oscillator for ringing power
converter
VRING Input for ringing signal
THA
Threshold adjustment for ringing
frequency detector
RFDO Output of ringing frequency detector
LIDET Line detect; output is low when the
line current is more than 15 mA
RECO 2 Inverting output of receiving
amplifier
STI S Input for side tone network (short
loop) or for answering machine
STI L Input for side tone network (long
loop)
RAC
Input of receiving amplifier for ac
coupling in feedback path
RECO 1 Output of receiving amplifier
TTXA Time constant of anticlipping in
transmit path
RECIN Input of receiving path; input
impedance is typically 80 k
W
TXIN Input of intermediate transmit stage,
input resistance is typically 20 kΩ
TLDI Transmit level detector input
TLDO Time constant of level detector for
transmit voice recognition
TS
Time constant for switching
Rev. A1: 12.07.1995
Preliminary Information
3 (11)
TELEFUNKEN Semiconductors
U4091B
Electrical Characteristics
f = 1 kHz, 0 dBm = 775 mV
rms
, I
M
= 0.3 mA, I
MP
= 2 mA, RDC = 130 k
W
, T
amb
= 25°C,
Z
ear
= 68 nF + 100
W
, Z
M
= 68 nF, unless otherwise specified.
Parameters
DC characteristics
DC voltage drop over circuit
Test Conditions / Pin
I
L
= 2 mA
I
L
= 14 mA
I
L
= 60 mA
I
L
= 100 mA
Symbol
V
L
4.6
8.8
Min.
Typ.
2.4
5.0
7.5
9.4
Max.
Unit
Figure
5.4
10.0
V
Transmission amplifier, I
L
= 14 mA, V
MIC
= 2 mV, RGT = 27 k
W
, unless otherwise specified
Adjustment range of transmit
G
T
36
52
gain
Transmitting amplification
G
T
47
48
49
Frequency response
I
L
14 mA,
D
G
T
0.5
f = 300 to 3400 Hz
Gain change with current
Pin 31 open
D
G
T
0.5
I
L
= 14 to 100 mA
Gain deviation
T
amb
= – 10 to + 60
°C
D
G
T
0.5
CMRR of microphone
CMRR
60
80
amplifier
Input resistance of MIC
RGT = 12 k
W
R
i
50
amplifier
RGT = 27 k
W
75
45
110
Distortion at line
I
L
> 14 mA
d
t
2
V
L
= 700 mVrms
Maximum output voltage
I
L
> 19 mA
V
Lmax
1.8
3
4.2
d < 5%
Vmic = 25 mV
CTXA = 1
m
F
dB
dB
dB
dB
dB
dB
k
W
%
dBm
w
"
"
"
Noise at line psophomet-
rically weighted
Anti-clipping attack time
release time
Gain at low operating current
Distortion at low operating
current
Line loss compensation
Mute suppression
a) MIC muted (microphone
preamplifier
p
p
b) TXA muted (second
stage)
I
L
> 14 mA
G
T
= 48 dB
CTXA = 1
m
F
each 3 dB overdrive
I
L
= 10 mA
I
MP
= 1 mA
RDC = 68 k
W
Vmic = 1 mV
I
M
= 300
m
A
I
L
= 10 mA
I
M
= 300
m
A
I
MP
= 1 mA
RDC = 68 k
W
Vmic = 10 mV
I
L
= 100 mA
I
L
14 mA
Mutx = open
no
– 80
0.5
9
G
T
40
–72
dBmp
ms
42.5
dB
d
t
5
%
w
D
G
TI
G
TM
– 6.4
60
– 5.8
80
– 5.2
dB
dB
IMPSEL = open
G
TTX
60
dB
Rev. A1: 12.07.1995
Preliminary Information
5 (11)
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