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PDF MSAN-156 Data sheet ( Hoja de datos )
| Número de pieza | MSAN-156 | |
| Descripción | Implementation Details | |
| Fabricantes | Mitel Networks | |
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Contents
1. Overview
2. Loop Current
2.1 Programming
2.2 Power Down
2.3 Overcurrent Fault Protection
3. Ringing
3.1 Supply voltages
3.2 Square wave ringing
4. Gain, Input and Balance Impedances
4.1 Programming
4.2 VX and VR signals
5. Metering Injection
6. Relay Drive
7. Protection
8. Power supply considerations
Application Note MSAN-156
Implementation Details for the
MH88617 SLIC
AN5028
1.0 Overview
ISSUE 2
September 1998
The MH88617 is a highly featured Subscriber Line
Interface Circuit (SLIC). It provides a total analogue
transmission and signalling link between a switching
system and a subscriber loop.
Typical applications include PABX and Key
Telephone Systems, Analog Terminal Adaptors, Pair-
Gain, Fibre in the Loop and Wireless Local Loop
systems.
This Application Note is intended to assist the user in
implementing the MH88617 as an analogue line
interface component in a communications system
and should be read in conjunction with the data
sheet for the MH88617.
2.0 Loop Current
The MH88617 employs a complex feedback network
to provide a constant current feed to the line. The
loop current can be programmed, via the ’LCA’ pin,
between 14mA and 55mA.
2.1 Programming
The MH88617 is designed to provide 24mA of
constant loop current by simply leaving the LCA pin
open circuit.
The loop current can be programmed above 24mA
by connecting a resistor between LCA and VCC.
Similarly, to program the loop current below 24mA a
resistor needs to be connected between LCA and
GND.
Internally, the MH88617 LCA pin can be depicted as
shown in Figure 1.
1
1 page  
Application Note
-48V
+5V
VBAT
DCRI
T
MH88617
R
RC
Ringing
Control
RV
MSAN-156
ANALOGUE
TELEPHONE
Ringing Input Signal
>2.8V Peak to Peak
Figure 5 - Square Wave Ringing on a Short Loop
3.2 Square Wave Ringing
The MH88617 is capable of providing square wave
ringing over a short loop (≤600 Ohms including the
telephone set) using a low voltage DCRI supply and
a square wave input at RV. Figure 5 illustrates how
this can be achieved.
When using a square wave ringing input that has fast
rising and falling edges, audible clicks may be heard
on the line. To avoid this a filter can be used at the
RV input to remove the fast edges which cause the
problem. Figure 5 details how this can be
performed.
SHK debouncing is recommended to accommodate
10 to 20mS glitches on the SHK pin.
4.0 Gain, Input and Balance
Impedances
Due to the design architecture of the MH88617, the
Gains and Input and Balance impedances are inter-
related, e.g. a change in the programmed line
impedance will affect the gains and network balance
impedance.
Typical resistor configuration e.g.,
The Square Wave input at RV can be a TTL square
wave. Provided the TTL peak-to-peak amplitude can
be guaranteed to be greater than +2.8V then the
DCRI voltage can be as low as +5V. However, if the
TTL input cannot be guaranteed to have an
amplitude greater than +2.8V (peak-to-peak) the
DCRI voltage needs to be +12V.
The TTL signal needs to be AC coupled to ensure
that the ring tripping circuit functions correctly.
Provided either one of the two conditions above are
satisfied the MH88617 will provide 40VRMS of
Square Wave Ringing into a REN of 5, over a short
loop.
600R as shown in Figure 6 and
270R + 750R/150nF as shown in Figure 7
4.1 Programming
Table 2 gives programming components for different
countries and gain. For countries not included,
please call your regional applications group. It is
recommended that the components are placed as
close as possible to the SLIC for best results.
Figures 6 and 7 show the configuration of the
resistor networks.
5
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| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet MSAN-156.PDF ] | |
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