MITEL MH89728

MH89726/728

MT8972 Loop Extender Circuits
Advance Information
Features
ISSUE 2
November 1990
Ordering Information
•
•
•
•
•
•
Operates from single or dual power supply
MH89726 extends transmission performance
for the MT8972 (DNIC) at 160kbit/s line rate
MH89728 extends transmission performance
for the MT8972 (DNIC) at 80kbit/s line rate
MH89726 and MH89728 are pin for pin
compatible with each other
Compact SIL package
Over 6km loop range on 24 AWG
MH89726/728 10 Pin SIL Package
0°C to 70°C
Description
The MH89728 and MH89726 are thick film hybrid
devices which may be used to extend the operating
range of the MT8972 (DNIC). The hybrids combine
signal equalization and amplification for the receive
and transmit paths on each device.
Applications
•
•
•
•
Digital subscriber lines
Digital PABX line cards and telephone sets
High speed, limited distance modem
ISDN U - Interface
The small size of these hybrids makes them suitable
for line card or terminal use with the MT8972. The
gain of the transmit signal may be adjusted through
the use of an external resistor.
TXGAIN
Pre-
TXIN
TX
Equalizer
Amplifier
TXOUT
Phase
Compensator
RXOUT
RXIN -
Pre-
RX
Canceller
Amplifier
RXIN +
VBias
TEST
V+
V-
Figure 1 - Functional Block Diagram
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MH89726/728
Advance Information
TXGAIN
TXOUT
RXIN +
RXIN VVBias
V+
TEST
RXOUT
TXIN
1
2
3
4
5
6
7
8
9
10
Figure 2 - Pin Connections
Pin Description
Pin #
Pin Name
1
TXGAIN
Transmit Gain. To be connected to Pin 2. An increase in gain can be achieved by
connecting an external resistor REXT between Pin 1 and Pin 2. The resultant gain is
calculated using; A= (R/24) + 2.8, where A=Gain and R= REXT (kΩ).
2
TXOUT
Transmit Output. Connect to the termination network.
3
RXIN-
Negative Receive Signal. Connect to TXOUT, Pin 2.
4
RXIN+
Positive Receive Signal. Connected to line transformer.
5
V-
6
VBias
7
V+
8
TEST
Test. Used for production testing. Leave unconnected.
9
RXOUT
Receive Output. Connect to LIN (Pin 21) of MT8972.
10
TXIN
Transmit Input. Connect to LOUT (Pin 1) of MT8972.
9-128
Description
Negative power supply.
Internal Bias Voltage. Connect to GND through 0.33 µF for single power supplies.
Connect to GND directly for split power supplies.
Positive power supply.
MH89726/728
Advance Information
Functional Description
The LEC is powered typically from ±15 Volts if dual
power supplies are available. Alternately 0 to +30
Volts, or -30 to 0 Volts can be used if only a single
power supply is available.
The MH89726/728 are 10 pin SIL thick film hybrid
circuits that may be used to extend the loop range
capability of the MT8972 (DNIC). For a detailed
description of the DNIC, refer to the MT8972 data
sheet.
Applications
Figure 3 shows a typical connection diagram of the
MT8972 and MH89726/728. RXOUT and TXIN of the
LEC are connected to LOUT and LIN of the DNIC
respectively. Pins 5, 6 and 7 are the power supply
pins, with the voltages being supplied as indicated in
the table . An external resistor, REXT, may be used
to increase the gain of the transmitter. Without REXT,
TXGAIN and TXOUT are shorted together resulting in
a transmit power level of +10 dBm.
Figure 1 shows a block diagram of the Loop
Extender Circuit (LEC). The LEC takes the line
signal which is transmitted by the DNIC on LOUT, preequalizes, and amplifies it before sending it to the
termination network. The gain of the TX amplifier is
adjustable by using an external resistor between
pins 1 and 2. If no external resistor is added, TXGAIN
and TXOUT must be shorted together, and the default
gain condition exists. This gain results in a transmit
signal power level of +10 dBm.
RLL, RL, and CL comprise the termination network
and are used to match the characteristic impedance
of the transmission line. This provides the 4 wire to 2
wire hybrid conversion necessary for twisted pair
transmission.
On the receive side, the LEC receives the differential
line signal from the transformer, and performs firstorder pre-cancellation as well as gain and phase
adjustment of the receive signal. The signal is then
output on RXOUT which is connected to LIN of the
MT8972.
Figure 4 shows a typical application of the LEC. On
short loops, jumpers (or switches) could be used to
remove the LEC from the circuit. For longer loops,
the jumpers could be changed to include the LEC in
the signal path.
Tables 1 and 2 show typical results obtained by
using the LEC with the MT8972. Actual distance
achieved may vary depending on the characteristics
of the transmission cable being used.
Most
important factors include cable attenuation (dB/km),
bridged taps, and crosstalk interference.
D1, D2 IN5817
Rext Set for different gain requirements
MH89726
or
MH89728
RLL
RL
CL
+ 5V
10
9
8
7
6
5
4
3
2
22
1
Rext
1
MH89726
160 kbit/s
MH89728
80 kbit/s
3.9kΩ, 5%
430Ω, 2%
15nF, 5%
3kΩ, 5%
430Ω, 2%
12nF, 5%
RLL
To Power Supplies
MT8972
(DNIC)
RL
D1
21
11
D2
Pin 6
(VBias)
Pin 5
(V-)
+ 15V
DUAL
GND
GND
SINGLE
GND*
+ 30V
SINGLE
GND*
*Use 0.33µF capacitor to GND
- 15V
- 30V
GND
Power
Supply
Pin 7
(V +)
CL
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
1.0µF
100kΩ
0.33µF
Figure 3 - Typical Connection Diagram for MT8972 and MH89726/728
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MH89726/728
Advance Information
MH89726 (160 kbit/s)
CONFIGURATION
CABLE
24 AWG
(8.0 dB/km at 120 kHz)
26 AWG
(11.5 dB/km at 120 kHz)
DNIC to DNIC
0.0 to 4.1 km
0.0 to 3.0 km
DNIC with LEC to DNIC with LEC
0.65 to 5.1 km
0.5 to 3.6 km
Table 1 - Typical Transmission Performance at 160 kbit/s
MH89728 (80 kbit/s)
CONFIGURATION
CABLE
24 AWG
(6.9 dB/km at 60 kHz (Note 1)
26 AWG
(10.0 dB/km at 60 kHz)
DNIC to DNIC
0.0 to 5.2 km
0.0 to 3.4 km
DNIC with LEC to DNIC and LEC
0.9 to 6.5 km
0.65 to 4.1 km
Table 2 - Typical Transmission Performance at 80 kbit/s
Note 1: The attenuation of the cable as specified by Bell System Technical Reference PUB 62411.
CB
80 kbit/s RA = 390Ω CA = 22nF CB = 3.3nF
160 kbit/s RA = 390Ω CA = 22nF CB = 1.5nF
MT8972
1
LOUT
RA
CA
+5V
2:1
D1
LIN 21
LEIN
LOOP
EXTENDER
and
Network
Termination
D2
1.0µF
LEOUT1
Twisted Pair
Copper 24-26
Gauge
LEOUT2
0.33µF
NOTES:
-D1, D2 IN5817 (Schottky)
-Solid jumpers used to connect the loop extender
-Dotted jumpers connect MT8972 without loop extender
Figure 4 - Typical Application of the Loop Extender
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MH89726/728
Advance Information
Recommended Operating Conditions
Characteristics
Sym
Min
Typ
Max
Units
Test Conditions
1
+ 15 V Supply
VDD
13.5
15.0
16.5
V
Note 1
2
- 15 V Supply
VSS
-16.5
-15.0
-13.5
V
Note 2
3
Standby Current
IS
3.0
mA
Note 1: A single voltage supply of +30V±10% can be used on VDD with VBias grounded through a 0.33 µF capacitor and V SS
grounded.
Note 2: A single voltage supply of -30V±10% can be used on VSS with VBias grounded through a 0.33 µF capacitor and V DD
grounded.
A.C. Electrical Characteristics
Characteristics
Sym
Min
Typ
Max
Units
Test Conditions
1
Active Current
IA
7.0
mA
@ 60 kHz for 80 kbit/s
@120 kHz for 160 kbit/s
2
TX Gain
ATX
9.0
dB
@ 60 kHz for 80 kbit/s
@120 kHz for160 kbit/s
3
TX Phase Angle
ΦTX
-170.0
°
@ 60 kHz for 80 kbit/s
@120 kHz for 160 kbit/s
4
RX Gain
ARX
0.0
dB
@ 60 kHz for 80 kbit/s
@120 kHz for160 kbit/s
5
RX Phase Angle
ΦRX
12.0
°
@ 60 kHz for 80 kbit/s
@120 kHz for160 kbit/s
6
Line Power
10.0
dBm
With 2:1 transformer
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MH89726/728
Advance Information
0.140 (0.356)
1.020 - 0.980 (2.590 - 2.490)
0.405 - 0.345
(1.029 -0.876)
0.190 - 0.180
(0.483 - 0.457)
0.01 (0.025)
0.105 - 0.095
(0.241 - 0.267)
0.025 - 0.015
(0.064 - 0.038)
All dimensions are in inches (centimeters).
Figure 4 - Mechanical Data
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