MT91600 Mitel Networks Corporation, MT91600 Datasheet - Page 3

• Manufacturer Part Number: MT91600
• Description: Programmable Slic
• Manufacturer: Mitel Networks Corporation

Preliminary Information
Functional Description
The MT91600 is the analog SLIC for use in a 4 Wire
switched system. The SLIC performs all of the
normal interface functions between the CODEC or
switching system and the analog telephone line such
as 2W to 4W conversion, constant current feed,
ringing and ring trip detection, current limiting, switch
hook indication and line and network balance
impedance
components.
Refer to Figure 5 for MT91600 components
designation.
2 Wire to 4 Wire Conversion
The hybrid performs 2 wire to 4 wire conversion by
taking the 4 wire signal from an analog switch or
voice CODEC, a.c. coupled to V
to a 2 wire differential signal at tip and ring. The 2
wire signal applied to tip and ring by the telephone is
converted to a 4 wire signal, a.c. coupled to Vx which
is the output from the SLIC to the analog switch or
voice CODEC.
Gain Control
It is possible to set the Transmit and Receive gains
by
components.
The gains can be calculated by the formulae:
2W to 4W gain:
Gain 2 - 4 = 20*Log [ R13 / R12]
Pin Description (continued)
Pin #
22
23
24
25
26
27
28
the
selection
Name
RLYC
RLYD
GND
setting
SHK
VEE
X2
C1
of
Gain Node 2. Networks, either resistive or complex, are connected between this node,
VR and GND to set the Network Balance Impedance for the SLIC.
A filter capacitor for ring trip is connected between this pin and GND.
Switch Hook (Output). This pin indicates the line state of the subscribers telephone.
The output can also be used for dial pulse monitoring. SHK is high in off-hook state.
Relay Control (Input). An active high on this pin will switch RLYD low.
Inverted Output of RLYC. It is used to drive the bipolar transistor that drives the relay
(see Figure 5.)
Ground. Return path for +5V and -5V. This should also be connected back to the
return path for the loop battery, LGND and relay drive ground RLYGND.
Negative supply rail, -5V.
using
the
appropriate
R
minimal
, and converting it
external
external
4W to 2W gain:
Gain 4 - 2 = 20*Log [0.891 * (R14 / R15)]
Impedance Programming
The MT91600 allows the designer to set the device’s
impedance across TIP and RING, (Z
network balance impedance, (Z
external low cost components.
For a resistive load, the impedance (Z
R11 and R18. For a complex load, the impedance
(Z
The network balance, (Z
(see Figure 5.)
The
calculated once the 2W - 4W gain has been set.
Line Impedance
For
impedance of the line, (Z
impedance across TIP and RING, (Z
match. Therefore:
Z
The relationship between Z
that set Z
Z
where kZ
Z
Z
LZ
LZ
o
o
TR
Description
= Z
/ ( R1+R2) = kZ
= R18, for a resistive load.
= [R18 + (R19 // C8)], for a complex load.
) is set by R11, R18, R19 & C8 (see Figure 5.)
optimum
TR
network
o
TR
= Z
is given by the formula:
LZ
balance
performance,
o
/ R11
NB
), is set by R16, R17 & C3
impedance
o
o
), and the device’s
and the components
NB
the
), separately with
MT91600
characteristic
TR
TR
should
) is set by
TR
), should
), and
be
3