Features
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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
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Voice Switch
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Interface for Answering Machine and Cordless Phone
Applications
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Feature Phone
Answering Machine
Fax Machine
Speaker Phone
Cordless Phone
Programmable
Telephone
Audio
Processor
U4091BM-N
Benefits
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No Piezoelectric Transducer for Tone Ringing Necessary
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Complete System Integration of Analog Signal Processing on One Chip
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Very Few External Components
Description
The programmable telephone audio processor U4091BM-N is a linear integrated cir-
cuit 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 nec-
essary for signal amplification and adaptation to the line. The U4091BM-N 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,
acoustic feedback during loudhearing can be reduced significantly. The generated
supply voltage is suitable for a wide range of peripheral circuits.
Rev. 4666B–CORD–08/04
U4091BM-N
Pin Description
Pin
Symbol
Function
Receive amplifier input
(1)
Time constant adjustment for transmit anti-clipping
Microphone input for hands-free operation
Input of symmetrical microphone amplifier with high common-mode rejection ratio
Input of symmetrical microphone amplifier with high common-mode rejection ratio
Output of the receive amplifier
Output of the receive amplifier, also used for sidetone network
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.
Positive supply-voltage input to the device in speech mode
Input for sensing the available line current
Ground, reference point for DC and AC signals
Unstabilized supply voltage for speech network
Negative output of speaker amplifier (push-pull only)
Positive output of speaker amplifier (single ended and push-pull operation)
Unregulated supply voltage for the microcontroller (via series regulator to VMP)
Regulated output voltage for supplying the microcontroller (typically 3.3 V/6 mA in speech mode)
Reference node for microphone amplifier, supply for electret microphones
Time constant for speaker amplifier anti-clipping
Input for ringer supply
Input for adjusting the ringer input impedance
70-kHz oscillator for ringing power converter
Output for driving the external switch resistor
Interrupt line for serial bus
Clock input for serial bus
Data line for serial bus
Input for 3.58-MHz oscillator
Reset output for the microcontroller
Clock output for the microcontroller
Input for external supply indication
Input of A/D converter
Output of background-noise monitor receive
Output of background-noise monitor transmit
Time constant for mode switching of voice switch
Time constant of receive-level detector
Input of receive-level detector
Input of transmit-level detector
Time constant of transmit-level detector
Switch for additional line impedance
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
Note:
RECIN
TXACL
MIC3
MIC2
MIC1
RECO2
RECO1
IND
VL
SENSE
GND
VB
SAO2
SAO1
VMPS
VMP
VMIC
TSACL
VRING
IMPA
COSC
SWOUT
INT
SCL
SDA
OSCIN
RESET
OSCOUT
ES
ADIN
BNMR
BNMT
CT
TLDR
INLDR
INLDT
TLDT
IMPSW
1. The protection device at Pin RECIN is disconnected.
5
4666B–CORD–08/04