MT8840AE [MITEL]
ISO2-CMOS Data Over Voice Modem; ISO2 -CMOS数据超过语音调制解调器
| 型号： | MT8840AE |
| 厂家： | 
MITEL NETWORKS CORPORATION |
| 描述： | ISO2-CMOS Data Over Voice Modem |
| 文件： | 总8页 (文件大小：60K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
ISO2-CMOS
MT8840
Data Over Voice Modem
ISSUE 4
November 1990
Features
Ordering Information
•
Performs ASK (amplitude shift keyed)
modulation and demodulation
MT8840AE
MT8840AS
18 Pin Plastic DIP
18 Pin SOIC
•
•
•
•
•
•
•
•
32 kHz carrier frequency
0°C to +85°C
Up to 2 kbit/s full duplex data transfer rate
On-chip oscillator
Description
On-chip tone caller for alerting functions
Adjustable tone caller frequencies
Selectable self-loop test mode
5V/2.5mA power supply
The MT8840 is a carrier over voice modem which
allows simultaneous transfer of voice and data over
a single pair of wires. Data is transferred on an
amplitude shift keyed (ASK) 32 kHz carrier. On-chip
filters remove voice frequency signals from the
received composite voice and data signal prior to
demodulation. The modulating signal is a bit stream
with a typical data rate of 2 kbit/s. In addition, the
device contains a two tone warbler which functions
2
ISO -CMOS and switched capacitor
technologies
•
18 Pin DIP
Applications
as a telephone ringer. The device is fabricated in
2
MITEL’s
double-poly
ISO -CMOS
technology
utilizing switched-capacitor techniques.
•
Simultaneous data and voice communication in
PABXs
•
•
2 kbit/s data modem
"Smart" telephone sets
ETC
MTC FATC
OSC1
OSC2
CK32
Timing
and
Control
Tone
Caller
TCO
R
O
U
T
I
TX Post-
Filter
TX Bandpass
TxO
TxDI
Modulator
Filter
RxE
RxI
RX Pre-
Filter
RX Bandpass
Filter
N
G
RxDO
AGC
Demodulator
DET
CRx
VDD
VSS
VRef
LOOP
Figure 1 - Functional Block Diagram
5-3
MT8840 ISO2-CMOS
18
17
16
15
14
13
12
11
10
1
2
3
4
5
6
7
8
9
DET
CRx
Rxl
VDD
RxDO
OSC2
OSC1
CK32
ETC
MTC
TCO
FATC
RxE
LOOP
VRef
TxO
TxDI
VSS
18 PIN PLASTIC DIP/SOIC
Figure 2 - Pin Connections
Description
Pin Description
Pin #
Name
1
DET
Demodulator detection level adjust input (Analog). Internal resistor divider applies
2.36V in open circuit condition. Connection of external resistor will vary detect level.
2
3
CRx
RxI
External AGC time constant adjust input (Analog). Connect external capacitor to V
.
SS
Modulated receive signal input (Analog). Biased at V
.
Ref
4
RxE
Receive enable input (Digital) with internal pull up. Active high.
Self-test mode select input (Digital) with internal pull down. Active high.
Internal reference supply voltage input (Analog) .
Modulated transmit carrier output (Analog).
5
LOOP
6
V
Ref
7
TxO
8
TxDI
Transmit data input (Digital).
9
V
Negative power supply.
SS
10
11
12
13
14
15
16
17
18
FATC
TCO
Tone caller center frequency adjust input (Analog).
Tone caller output (Digital).
MTC
Mute tone caller input (Digital) with internal pull down. Active high.
Enable tone caller input (Digital) with internal pull down. Active high.
32 kHz data strobe output (Digital).
ETC
CK32
OSC1
OSC2
RxDO
Clock Input
3.579545 MHz crystal connected between
these pins completes internal oscillator.
Clock Output to drive external devices.
Receive data output (Digital). Synchronized to CK32.
Positive power supply.
V
DD
5-4
ISO2-CMOS MT8840
Functional Description
Applications
The MT8840 contains the modulator and
demodulator circuitry for 32 kHz ASK signalling as
well as a two-tone warbler (tone caller) to replace the
function of the mechanical telephone ringer.
Figures 3 through 5 show how the MT8840 may be
utilized to transfer data and voice simultaneously
over a single pair of wires in digital or analog PABXs
and "smart" telephone sets. In all three figures a
microprocessor sends/receives data to/from the
MT8840 via a UART which converts the data format
A 32 kHz carrier is 100% amplitude modulated by the
digital bit stream applied to input TxDI. This results in
an amplitude shift keyed (ASK) 32 kHz carrier. A
logical high at TxDI disables the carrier and a logical
low enables it. The digitally modulated waveform is
shaped by the Tx BANDPASS FILTER and smoothed
by the Tx POST FILTER. The signal then enters the
routing block where it is transferred to the TxO
output.
from parallel-to-serial or serial-to-parallel for
the
transmit and receive directions, respectively. In the
receive direction the MT8840 has on-board filters to
reject voice-band signals leaving only the 32 kHz
carrier. This carrier is then demodulated to recover
the received data. In the transmit direction the data
to be sent is modulated and passed on to a summing
circuit which sums the modulated 32 kHz carrier and
voiceband signals for transmission over the
telephone line. In the PABX the Filter/Codec has
filters which reject the 32 kHz carrier from the
received composite voice and data signal allowing
only voiceband signals to pass through which are
then PCM encoded for digital switching. However, in
both the analog PABX and smart telephone set,
lowpass filters could be included to bandlimit the
received signal leaving only voice signals to be
passed on to the switch array or handset earpiece.
The modulated 32 kHz receive signal is applied to
RxI. With a logical low applied to LOOP and a logical
high applied to RxE, receive signals are routed to the
Rx PREFILTER. High frequencies are removed by
the Rx PREFILTER to prevent aliasing in the
switched capacitor Rx BANDPASS FILTER. Voice
signals are removed by the bandpass filter which is
followed by an AGC circuit. This provides a dynamic
range of 20dB for the receiver. An external 1µF
capacitor connected from CRx to V
is required to
SS
control the AGC attack and decay time constants.
Data is recovered from the received signal in the
demodulator. The minimum voltage level to which
the demodulator responds may be adjusted by
connecting a resistor from DET to V
or V . Since
DD
Ref
DET is the input to a comparator, noise should be
kept to a minimum at this pin. The recovered receive
data is synchronized to the leading edge of the 32
kHz clock (available at CK32) before appearing at
RxDO.
When in loop around mode, the Rx PREFILTER
input is internally disconnected from the RxI input pin
and connected to TxO. The transmitter output is still
available at TxO.
A two tone warbling audio signal is available at TCO
when the tone caller enable input (ETC) is high. TCO
is internally clamped to V
when the tone caller is
Ref
disabled. The tone output can be attenuated by 20dB
if a logical high is applied to the tone caller mute
input (MTC).
5-5
MT8840 ISO2-CMOS
Tx Data
Rx Data
Tx
Micro-
processor
UART
MT8840
Summing
Circuit
Rx
2W/4W
Converter
Telephone
line
PCM
Highway
Tx
FILTER/
CODEC
(MT896X)
Rx
Figure 3 - Digital PABX Block Diagram
Tx Data
Rx Data
Tx
Micro-
UART
MT8840
processor
Summing
Circuit
Rx
(Optional)
2W/4W
Converter
Telephone
line
Low-
Pass
Filter
Rx
Analog
Switch
Array
(MT8804)
To
Another
Telephone
Extension
SLIC
Tx
Figure 4 - Analog PABX Block Diagram
5-6
ISO2-CMOS MT8840
Tx Data
Rx Data
Tx
Micro-
processor
UART
MT8840
Summing
Circuit
Rx
2W/4W
Converter
Telephone
line
Handset
Low-
Pass
Filter
(Optional)
Figure 5 - Smart Telephone Set Block Diagram
VDD
OSC1
MT8840
OSC2
MT8840
MT8840
C=33pF
OSC1
OSC2
OSC1
• • •
C=1000pF
OSC2
C=1000pF
VSS
When a single crystal is shared among a number of MT8840 devices, OSC1 and OSC2 should be a.c. coupled with a 1000
pF capacitor as shown above. This capacitor is not needed between the device with the crystal and the first driven device.
A capacitor should be used in the first stage whenever such a chain of devices is driven from a clock instead of a crystal. A
33pF capacitor should be connected between OSC1 and VSS to compensate for the load on OSC2.
Figure 6 - Crystal Oscillator Connections for Driving Multiple MT8840s
5-7
MT8840 ISO2-CMOS
Absolute Maximum Ratings*
Parameter
Symbol
-V
Min
Max
Unit
1
2
3
4
5
Supply Voltage
V
-0.3
+7.0
V
V
DD SS
Voltage On Any Pin
Current On Any Pin
Storage Temperature
Package Power Dissipation
V
V
-0.3
V
+0.3
DD
Max
Max
SS
I
20
mA
°C
T
-65
+150
850
S
P
mW
Diss
* Exceeding these ratings may cause permanent damage. Functional operation under these conditions is not implied.
Recommended Operating Conditions
Parameter
Symbol
Min
Typ
Max
Unit
1
2
3
4
5
6
7
Operating Supply Voltages
V
V
4.75
5
5.25
V
V
DD
Ref
DD
Ref
0.4V
DD
Operating Supply Currents
I
2.5
5.0
200
+85
50
mA
µA
°C
pF
KΩ
I
Operating Temperature
Load Capacitance (TxO)
Load Resistance (TxO)
T
0
O
C
R
L
L
10
D.C. Characteristics - VDD = 5.0 V ± 5% VSS =0V T = 0 - 85oC (All voltages are referenced to VSS /GND)
Characteristics
Input Current
Sym
Min
Typ
Max
Unit
Test Conditions
= 0 to V
1
2
I
±10
1.5
5.0
0.4
µA
V
V
IN
IN
DD
D
I
G
I
T
A
L
Input Low Voltage
V
0
IL
3
Input High Voltage
V
V
3.5
V
IH
4
Output Low Voltage
Output High Voltage
Output Drive Current
N Channel Sink (Except OSC2)
OSC2
V
I
= 0.4mA
= 0.4mA
OL
OL
5
V
4.6
V
I
OH
OH
6
7
I
0.4
0.1
0.4
0.1
mA
mA
mA
mA
µA
KΩ
KΩ
KΩ
pF
pF
pF
Ω
V
V
V
= 0.4V
= 4.6V
OL
OL
I
/
O
8
9
P Channel Source (Except OSC2)
OSC2
I
OH
OH
10
11
12
13
14
15
16
17
18
19
20
21
22
Input Current (RxI, FATC)
Input Resistance (FATC)
I
±10
= 0 to 5.0V
IN
IN
R
500
IN
IN
(DET to V
(DET to V
)
170
23
DD
A
N
A
L
O
G
)
Ref
Input Capacitance (RxI)
(FATC)
C
50
10
Any Digital Input
Output Resistance (TxO)
(TCO)
5.0
100
3
7.5
R
O
I
/
O
KΩ
KΩ
mV
V
MTC = 0
MTC = 1
(TCO)
30
Output Offset Voltage (TxO)
Output Voltage (DET)
V
V
±25
2.36
±200
2.55
O
O
2.20
See Note 1
Notes: 1. Voltage specified is generated internally and measured with no external components connected to DET
5-8
ISO2-CMOS MT8840
A.C. Characteristics - VDD=5.0V±5% VSS=0V T=0 - 85°C (All voltages are referenced to VSS/GND)
Characteristics
Sym
Min
Typ
Max
Unit
Test Conditions
1
Crystal/Clock Frequency
Clock Input (OSC 1)
Rise Time
f
C
3.5759 3.5795 3.5831 MHz OSC1, OSC2
2
3
t
100
100
60
ns
ns
%
10% - 90% of (V - V
)
LHCI
DD
SS
4
Fall Time
t
HLCI
D
I
G
I
T
A
L
5
Duty Cycle
DC
40
50
CI
6
Clock Output (OSC 2)
Rise Time
7
t
100
100
50
ns
ns
%
C = 30pF, 3.58MHz ext.
LHCO
HLCO
L
8
Fall Time
t
clock to OSC1
9
Duty Cycle
DC
CO
LCO
C32
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
39
40
41
42
43
Capacitive Load
Clock Output (CK32)
Rise Time
C
F
30
pF
I
/
O
32508 32541 32574
Hz fc = 3.5795MHz
t
100
ns
ns
%
10% - 90% of (V - V
)
LH32
DD
SS
Fall Time
t
100
C = 100pF
L
HL32
Duty Cycle
DC
50
100
32
Capacitive Load
Warbler Frequency (TCO)
Low Tone Frequency
C
pF
L32
f
7.935 7.945 7.955
Hz fc = 3.5795MHz ± 0.1%
Hz FATC = 0, f = 3.5795MHz
W
f
352
1036
440
390
1148
487
428
1260
535
LT
c
T
O
N
E
Hz FATC = V , f = 3.5795MHz
DD
c
High Tone Frequency
f
Hz FATC = 0, f = 3.5795MHz
c
HT
1295
1434
1.25
1574
Hz FATC = V , f = 3.5795MHz
DD c
Harmonic Relationship
Warbler Output (TCO)
Rise Time
f
/f
HT LT
C
A
L
L
E
R
t
500
500
50
ns
ns
%
100KΩ load to V
Ref
LHWO
Fall Time
t
C = 30pF, MTC = 0
HLWO
L
Duty Cycle
DC
WO
Output Level (TCO)
V
V
V
MTC = 0
TCC
DD
pp
pp
0.625
32541
250
V
MTC = 1 (100KΩ load to VRef)
Modulated Frequency
Output Level (TxO)
Output Level (TxO)
f
Hz
mV
MOD
M
O
D
U
L
A
T
O
R
V
225
270
V
= 5V
DD
TxO
pp
variation vs. V
V
100
%
DD
TxO
Transmit Data Input (TxDI)
Rise Time
t
100
100
ns
ns
LHTxDI
Fall Time
t
HLTxDI
Data Rate (TxDI)
Input Impedance (RxI)
Valid Input Level - Data (RxI)
Valid Input Level - Data + Voice
Receive Data Output (RxDO)
Rise Time
f
2
k/bits See Note 1
Data
Z
50
KΩ 32 kHz Input Frequency
D
E
M
O
D
U
L
A
T
O
R
IN
V
V
40
40
400
3.0
mV
V
See Note 2
pp
RxI
RxI
pp
f
2
kbit/s
ns
Data
100
100
10% - 90% of (V - V
)
DD
SS
Fall Time
ns
C = 100pF
L
Capacitive Load
100
60
pF
Duty Cycle
50
%
Notes: 1.
2.
All A.C. parameters are based on a typical data rate of 2 kbit/s.
Measured with no external resistor to DET input. Detection level internally set to 2.36V typical.
5-9
MT8840 ISO2-CMOS
A.C. Characteristics (Continued)
Characteristics
Sym
Min
Typ
Max
Unit
Test Conditions
44
45
46
47
Inband Noise Rejection (S/N)
Attenuation to Voice Signals
Detect Filter Q
12
40
dB Input Sig. (RxI) = 400mV
D
E
M
O
D
pp
dB f = 0 - 5KHz
in
Q
3.8
32
Detector Center Frequency
kHz
Notes: 1.
2.
All A.C. parameters are based on a typical data rate of 2 kbit/s.
Measured with no external resistor to DET input. Detection level internally set to 2.36V typical.
5-10
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