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PDF U3900BM Data sheet ( Hoja de datos )
| Número de pieza | U3900BM | |
| Descripción | Programmable Telephone Audio Processor | |
| Fabricantes | ATMEL Corporation | |
| Logotipo |  |
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Programmable Telephone Audio Processor
U3900BM
Description
The programmable telephone audio processor U3900BM
is a linear integrated circuit for use in feature phones,
answering machines, fax machines and cordless phones.
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 U3900BM can also be supplied
via an external power supply. An integrated voice switch
with loudspeaker amplifier enables hands-free or loud-
hearing 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
mD Tone ringer interface with DC/DC converter
oD Speaker amplifier with anti-distortion
.cD Power-supply management, regulated, unregulated
and a special supply for electret microphone
D Voice switch
UD CLID + SCWID
t4D DTMF generator
D Switch matrix
eD Line current information
D Fully programmable
eD Watchdog
Benefits
D Savings of one piezoelectric transducer
D Complete system integration of analog signal
processing on one chip
D Very few external components
D Highly integrated solution
D Extremely versatile due to full programmability
Applications
Feature phone, answering machine, fax machine, speaker
phone, base station of cordless phone
taShSpeech
acircuit
.DDTMF
ww Tone
w ringer
Voice
switch
Serial
bus
Audio
amplifier
Clock
Data
Reset
MCU
Class
Ordering Information
Extended Type Number
U3900BM-AFN
U3900BM-AFNG3
Rev. A3, 31-Oct-00
.comPackage
t4USSO44
eSSO44
Remarks
Taped and reeled
www.DataSheTarget Specification
1 (36)
1 page  
U3900BM
2 Class Function
The U3900BM includes a class function Calling Line
IDentification (CLID) for on-hook and Spontaneous Call
Waiting IDentifier (SCWID) for off-hook status.
2.1 CLID
CLID is designed to demodulate CCITT V23 and BELL
202 (1200 bauds FSK asynchronous data) and is
compatible with both formats without external
intervention. It fulfils the CS B14-10W requirements.
The main feature of this part is to provide, for the user,
information about the caller before answering the call.
The information is a DATA message sent from the Central
Office (CO) to the CPE during the silent interval, and
after the first ringing burst.
2.1.1 Description
On the receive side, the received signal coming from
CLI1 and CLI2 first goes to an antialiasing filter after the
differential op-amp.
The next section is a bandpass filter composed of an FSK
filter composed of a fifth order high-pass followed by a
third order low-pass filter. The low-pass and high-pass
cut-off frequencies are about 300 Hz and 3400 Hz
respectively.
2.1.2 Carrier Detect
The carrier detect provides an indication (to the micro-
processor with an interrupt request) of the presence of a
signal in the FSK band. It detects a sufficient amplitude
signal at the output of the FSK bandpass filter.
Note that signals such as speech or DTMF tones also lie
in the FSK frequency band and the carrier detect may be
activated by these signals. The signals will be
demodulated and presented as DATA. To avoid false
DATA detection, a command bit is used to disable the
demodulator when no FSK signal is expected.
Four bits are provided to improve carrier detection
[CD_CD <3..0>]. With these bits it is possible to select
a capture window (see the tables next page), and avoid a
false detection.
With the use of SCD bit the carrier detect function is
improved, because after a normal carrier detection
(NCD), a part (10 bits) of the channel seizure is taken in
count before alerting the microprocessor.
Note:
When the CPE is off hook (SCWID mode) the CO sends
FSK data without channel seizure. The
mark signal = 80 bits ±10 at 1200 bauds (1300 Hz con-
tinuously during 67 ms).
For this case a selected bandpass 1000 Hz to 1700 Hz
could be very useful for the carrier detect ...
After the interrupt due to the carrier detect the micro-
processor can change the bandpass frequencies according
to the FSK band.
D The normal carrier detect guard time is 26.4 ms.
D The improved carrier detect guard time is 34.7 ms.
D The carrier lost guard time is 8.8 ms, in all the cases.
2.1.3 Demodulator
This part is enabled with the carrier detect signal.
The reference signal is at 1700 Hz, (the same frequency
for BELL 202 and V23). All the incoming signals are
compared to this value to make a digital square wave
frequency varying in frequency and in phase as a function
of the input frequencies.
2.1.4 Clock Recovery
The process starts at the first low-level bit received from
the demodulator. After that the CLOCK is generated for
the 10 serial bits (1 bit start, 8 bits data, 1 bit stop).When
all the data are received DATA READY is generated. This
signal loads the serial data in a parallel buffer.
DATA READY provides an indication (to the micro-
processor with an interrupt request) of the presence data
byte available.
Rev. A3, 31-Oct-00
Target Specification
5 (36)
5 Page 
U3900BM
CAS Detect Process (continued)
Improved process:
To prevent false detection from speech and music by the far and the near end (talk-off), and to detect the incoming CAS
signal from the CO, polluted with speech or music by the near end (talk-down), a new feature is used: the early and
up guard time.
CAS signal duration: 80 ± 5 ms
frequencies: 2130 Hz + 2750 Hz mixed with speech and music frequencies
Values permitted for drops after
a successful early guard time
IN SCWID
detector
Drops
In signal
Restart
Early
guard time
3 Drops had no effect (FDD = 4 ms, FDC = 4)
OUT SCWID
detector
Up guard time
Choice of 3
EGT values
Choice of 4
UGT values
Interrupt
to the µP
Figure 10. Timing diagram for early and up guard time
14610
Note: In the case above, the EGT counter restarts 3 times. After a sucessful 10.3-ms EGT, 3 drops occured but without
any effect because the duration and the number is less than the maximum permitted.
CAS signal duration: 80 ± 5 ms
frequencies: 2130 Hz + 2750 Hz mixed with speech and music frequencies
IN SCWID
detector
Filter values permitted for spikes
after a successful early guard time
Spikes
in signal
mixed with speech and music frequencies
Restart
Early guard time
5 Spikes had no effect (FDD = 4 ms)
OUT SCWID
detector
Choice of 3
EGT values
Down guard time
Choice of 4
DGT values
Interrupt
to the µP
Figure 11. Timing diagram of early and down guard time
14611
Note: In the case above, the EGT counter restarts 3 times. After a sucessful 13.7-ms EGT, 5 spikes occured but without
any effect because the duration is less than the maximum permitted.
Rev. A3, 31-Oct-00
Target Specification
11 (36)
11 Page | ||
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