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Электронный компонент: U4091BM

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U4091BM
Rev. A3, 27-Oct-00
1 (32)
Programmable Telephone Audio Processor
Description
The programmable telephone audio processor U4091BM
is a linear integrated circuit for use in feature phones,
answering machines and fax machines. It contains the
speech circuit, tone-ringer interface with DC/DC
converter, sidetone equivalent and ear-protection
rectifiers. The circuit is line-powered and contains all
components necessary for signal amplification and
adaptation to the line. The U4091BM can also be supplied
via an external power supply. An integrated voice switch
with loudspeaker amplifier enables hands-free or
loudhearing operation. With an anti-feedback function,
acoustical feedback during loudhearing can be reduced
significantly. The generated supply voltage is suitable for
a wide range of peripheral circuits.
Features
D Speech circuit with anti-clipping
D Tone-ringer interface with DC/DC converter
D Speaker amplifier with anti-distortion
D Power-supply management (regulated, unregulated)
and a special supply for electret microphone
D Voice switch
D Interface for answering machine and cordless phone
Benefits
D No piezoelectric transducer for tone ringing necessary
D Complete system integration of analog signal proces-
sing on one chip
D Very few external components
Applications
Feature phone, answering machine, fax machine, speaker
phone, cordless phone
Block Diagram
Speech
circuit
Voice
switch
Audio
amplifier
Serial
bus
DTMF
Tone
ringer
Clock
Data
Reset
MCU
Ordering Information
Extended Type Number
Package
Remarks
U4091BM-MFN
SSO44
U4091BM-MFNG3
SSO44
Taped and reeled
U4091BM
Rev
. A3, 27-Oct-00
2 (32)
Detailed
Block Diagram
5
4
3
DTMF/
melody
Filter
Offset
canceler
Offset
canceler
AMPB
RXLS
MIC
LRX
DTMF
AGCO
AMREC
AGCI
LTX
EPO
Switch matrix
AGC
AGARX
STBAL
TXACL
2
43
44
1
39
AGATX
42
9
38
17
15
16
12
22
21
19
20
40
41
7
6
18
SACL
14
13
AFS
control
BIDIR
serial
bus
1/8/16/32
DIV.
35
34
37
36
33
31
32
24
25
23
26
27 29 28
11
30
3.58 MHz
OSC.
MUX
ADC
REG
POR
Power
supply
Ringing
power
converter
10
8
V
L
V
RING
V
MIC
RECO1
MICO
V
MP
RA
SA
VMP
RFDO
LIDET
TXA
MICRO
C
Figure
1. Detailed block diagram
U4091BM
Rev. A3, 27-Oct-00
3 (32)
Pin Description
Pin
Symbol
Function
1
RECIN
Receive amplifier input
2
TXACL
Time-constant adjustment for
transmit anti-clipping
3
MIC3
Microphone input for hands-free
operation
4
MIC2
Input of symmetrical microphone
amplifier with high common-mode
rejection ratio
5
MIC1
Input of symmetrical microphone
amplifier with high common-mode
rejection ratio
6
RECO2
Output of the receive amplifier
7
RECO1
Output of the receive amplifier, also
used for sidetone network
8
IND
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 adjust the DC mask.
9
VL
Positive supply-voltage input to the
device in speech mode
10
SENSE
Input for sensing the available line
current
11
GND
Ground, reference point for DC-
and AC signals
12
VB
Unstabilized supply voltage for
speech network
13
SAO2
Negative output of speaker
amplifier (push-pull only)
14
SAO1
Positive output of speaker amplifier
(single ended and push-pull
operation)
15
VMPS
Unregulated supply voltage for the
microcontroller (via series regulator
to VMP)
16
VMP
Regulated output voltage for
supplying the microcontroller
(typ. 3.3 V/ 6 mA in speech mode)
17
VMIC
Reference node for microphone
amplifier, supply for electret
microphones
18
TSACL
Time constant for speaker amplifier
anti-clipping
Pin
Symbol
Function
19
VRING
Input for ringer supply
20
IMPA
Input for adjusting the ringer input
impedance
21
COSC
70-kHz oscillator for ringing power
converter
22
SWOUT Output for driving the external
switch resistor
23
INT
Interrupt line for serial bus
24
SCL
Clock input for serial bus
25
SDA
Data line for serial bus
26
OSCIN
Input for 3.58-MHz oscillator
27
OSC-
OUT
Clock output for the microcontroller
28
RESET
Reset output for the microcontroller
29
ES
Input for external supply indication
30
ADIN
Input of A/D converter
31
BNMR
Output of background-noise
monitor receive
32
BNMT
Output of background-noise
monitor transmit
33
CT
Time constant for mode switching
of voice switch
34
TLDR
Time constant of receive-level
detector
35
INLDR
Input of receive-level detector
36
INLDT
Input of transmit-level detector
37
TLDT
Time constant of transmit-level
detector
38
IMPSW
Switch for aditional line impedance
39
MICO
Microphone preamplifier output
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
Remark: The protection device at Pin RECIN is disconnected.
U4091BM
Rev. A3, 27-Oct-00
4 (32)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
STRC
STC
STO
AMPB
MICO
IMPSW
TLDT
INLDT
INLDR
CT
BNMT
BNMR
ADIN
ES
RESET
OSCOUT
OSCIN
SDA
SCL
INT
TXACL
MIC3
MIC2
MIC1
RECO2
RECO1
VL
SENSE
VB
VMPS
VMP
VMIC
TSACL
VRING
IMPA
COSC
SWOUT
SAO1
RECIN
AMREC
TLDR
SAO2
GND
IND
Figure 2. Pinning
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
SENSE
C
IND
(R
DC
R
30
) / (R
DC
+ R
30
)
The U4091BM contains two identical series regulators
which provide a supply voltage VMP of 3.3 V 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.
Supply Structure of the Chip
A main benefit of the U4091BM is the easy implementa-
tion of various applications due to the flexible system
structure of the chip.
Possible applications:
D Group listening phone
D Hands-free phone
D Phones which feature ringing with the built-in speaker
amplifier
D Answering machine with external supply
The special supply topology for the various functional
blocks is illustrated in figure 3.
There are four major supply states:
1.
Speech condition
2.
Power down (pulse dialing)
3.
Ringing
4.
External supply
1. In speech condition, the system is supplied by the line
current. If the LIDET-block detects a line voltage
above approximately 2 V, 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.
U4091BM
Rev. A3, 27-Oct-00
5 (32)
For line voltages below 2 V, the switches remain in
quiescent state as shown in the diagram.
2. When the chip is in power-down mode (Bit
LOMAKE), e.g., during pulse dialing, all internal
blocks are disabled via the serial bus. In this condition,
the voltage regulators and their internal bandgap are
the only active blocks.
3. During ringing, the supply for the system is fed into
VB via the Ringing Power Converter (RPC).
Normally, the speaker amplifier in single-ended mode
is used for ringing. The frequency for the melody is
generated by the DTMF/Melody generator.
4. In an answering machine, the chip is powered by an
external supply via Pin VB. The answering machine
connections can be directly put to U4091BM. The
answering machine is connected to the Pin AMREC.
For the output AMREC, an AGC function is select-
able via the serial bus. The output of the answering
machine will be connected to the Pin AMPB, which is
directly connected to the switching matrix, and thus
enables the signal to be switched to every desired
output.
+
+
3.3 V
5.5 V
V
MPS
V
MP
5.5 V
V
470
F
300 k
+
R
47
F
220
F
1
F
10
R
SENSE
R
IND
C
V
L
V
B
Figure 3. Supply generator
Ringing Power Converter (RPC)
The RPC transforms the input power at VRING (high
voltage/ low current) into an equivalent output power at
VB (low voltage/ high current) which is capable of
driving the low-ohmic loudspeaker. The input impedance
at VRING is adjustable from 3 k
to 12 k
by RIMPA
(ZRING = RIMPA / 100) and the efficiency of the step-
down converter is approximately 65%.
Ringing Frequency Detector (RFD)
The U4091BM provides an output signal for the
microcontroller. This output signal is always double the
value of the input signal (ringing frequency). It is
generated by a current comparator with hysteresis. The
levels for the on-threshold are programmable in 16 steps;
the off-level is fixed. Every change of the comparator
output generates a high level at the interrupt output INT.
The information can then be read out by means of a serial
bus with either normal or fast read mode. The block RFD
is always enabled.
RINGTH[0:3]
VRING
0
7 V
15
22 V
step
1 V
Clock Output Divider Adjustment
The Pin OSCOUT is a clock output which is derived from
the crystal oscillator. It can be used to drive a micro-
controller or another remote component and thereby
reduces the number of crystals required. The oscillator
frequency can be divided by 1, 8, 16, 32. During power-on
reset, the divider will be reset to 1 until it is changed by
setting the serial bus.
CLK[0:1]
Divider
Frequency
0
1
3.58 MHz
1
8
447 kHz
2
16
224 kHz
3
32
112 kHz
Serial Bus Interface
The circuit is controlled by an external microcontroller
through the serial bus.
The serial bus is a bi-directional system consisting of a
one-directional clock line (SCL) which is always driven
by the microcontroller, and a bi-directional data-signal
line. It is driven by the microcontroller as well as from the
U4091BM (see figure 23).
The serial bus requires external pull-up resistors as only
pull-down transistors (Pin SDA) are integrated.
WRITE:
The data is a 12-bit word:
A0 A3: address of the destination register (0 to 15)
D0 D7: content of the register
The data line must be stable when the clock is high. Data
must be shifted serially. After 12 clock periods, the write
indication is sent. Then, the transfer to the destination reg-
ister is (internally) generated by a strobe signal transition
of the data line when the clock is high.