MITEL MT89726, MT89728 Datasheet
9-127
Features
• 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
Applications
• Digital subscriber lines
• Digital PABX line cards and telephone sets
• High speed, limited distance modem
• ISDN U - Interface
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.
The small size of these hybrids makes them suitable
for line card or terminal use with the MT8972. The
gain of the t ransmit signal ma y be adjusted th rough
the use of a n ex te rn al r e sis t or.
Figure 1 - Functional Bloc k Diagram
TX
IN
RX
OUT
V
Bias
TEST V+V
-
RX
IN
-
RX
IN
+
TX
OUT
TX
GAIN
Pre-
Equalizer
Phase
Compensator
Pre-
Canceller
RX
Amplifier
TX
Amplifier
Ordering Information
MH89726/728 10 Pin SIL Package
0°C to 70°C
ISSUE 2 November 1990
MH89726/728
MT8972 Loop Extender Circuits
Advance In formation
9-128
MH89726/728 Advance Information
Figure 2 - Pin Conn ections
Pin Description
Pin # Pin Name Description
1TX
GAIN
Transmit Gain. To be connected to Pin 2. An increase in gain can be achieved by
connecting an external resistor R
EXT
between Pin 1 and Pin 2. The resultant gain is
calculated using; A= (R/24) + 2.8, where A=Gain and R= R
EXT
(kΩ).
2TX
OUT
Transmit Output. Connect to the termination network.
3RX
IN-
Negative Receive Signal. Connect to TX
OUT
, Pin 2.
4RX
IN+
Positive Receive Signal. Connected to line transformer.
5V-Negative power supply.
6V
Bias
Internal Bias Voltage. Connect to GND through 0.33 µF for single power supplies.
Connect to GND directly for split power supplies.
7V+Positive power supply.
8TESTTest. Used for production testing. Leave unconnected.
9RX
OUT
Receive Output. Connect to LIN (Pin 21) of MT8972.
10 TX
IN
Transmit Input. Connect to L
OUT
(Pin 1) of MT8972.
1
2
3
4
5
6
7
8
9
10
TXGAIN
TXOUT
RXIN +
RXIN -
V -
VBias
V +
TEST
RXOUT
TXIN
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