mh89726 Mitel, mh89726 Datasheet - Page 3

• Manufacturer Part Number: mh89726
• Description: Mt8972 Loop Extender Circuits Advance Information
• Manufacturer: Mitel

Advance Information
Functional Description
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).
description of the DNIC, refer to the MT8972 data
sheet.
Figure 1 shows a block diagram of the Loop
Extender Circuit (LEC).
signal which is transmitted by the DNIC on L
equalizes, 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, TX
and TX
gain condition exists. This gain results in a transmit
signal power level of +10 dBm.
On the receive side, the LEC receives the differential
line signal from the transformer, and performs first-
order pre-cancellation as well as gain and phase
adjustment of the receive signal. The signal is then
output on RX
MT8972.
Tables 1 and 2 show typical results obtained by
using the LEC with the MT8972.
achieved may vary depending on the characteristics
of the transmission cable being used.
important factors include cable attenuation (dB/km),
bridged taps, and crosstalk interference.
OUT
MT8972
(DNIC)
22
11
+ 5V
must be shorted together, and the default
OUT
1
21
which is connected to L
Figure 3 - Typical Connection Diagram for MT8972 and MH89726/728
D2
D1
10
The LEC takes the line
9
8
Power
Supply
DUAL
SINGLE
SINGLE
*Use 0.33 F capacitor to GND
To Power Supplies
7
Actual distance
For a detailed
6
MH89726
MH89728
Pin 7
(V +)
+ 15V
GND
+ 30V
5
or
IN
OUT
of the
4
, pre-
Most
GAIN
3
Pin 6
(V
GND
GND*
GND*
Bias
2
)
1
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.
Applications
Figure 3 shows a typical connection diagram of the
MT8972 and MH89726/728. RX
LEC are connected to L
respectively. Pins 5, 6 and 7 are the power supply
pins, with the voltages being supplied as indicated in
the table . An external resistor, R
to increase the gain of the transmitter. Without R
TX
a transmit power level of +10 dBm.
R
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.
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.
LL
R
Pin 5
(V-)
- 15V
- 30V
GND
GAIN
ext
, R
L
R
, and C
and TX
L
R
LL
C
L
OUT
L
comprise the termination network
D1, D2
R
R
R
C
ext
LL
L
L
are shorted together resulting in
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 AA AA
0.33 F
Set for different gain requirements
MH89726
160 kbit/s
3.9k , 5%
430 , 2%
15nF, 5%
OUT
IN5817
MH89726/728
1.0 F
100k
and L
OUT
EXT
IN
and T
, may be used
MH89728
80 kbit/s
3k , 5%
430 , 2%
12nF, 5%
of the DNIC
XIN
of the
9-129
EXT
,