MT91600
Pin Description (continued)
Pin #
16
17
18
19
20
21
22
23
24
25
26
27
28
Name
Z2
Z3
X1
VX
X3
VR
X2
C1
SHK
RLYC
RLYD
GND
VEE
Description
Data Sheet
Line Impedance Node 2.
This is the common connection node between Z1 and Z3.
Line Impedance Node 3.
A network either resistive or complex of scaled value "k" is
connected between Z3 and Z2. This connection can not be left open circuit.
Gain Node 1.
This is the common node between Z3 and VX where resistors are
connected to set the 2 W to 4 W gain.
Transmit Audio (Output).
This is the 4 W analog signal to the SLIC.
Gain Node 3.
This is the common node between VR and the audio input from the
CODEC or switching network where resistors are fitted to sets the 4 W to 2 W gain
Receive Audio (Input).
This is the 4 W analog signal to the SLIC.
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 +5 V and -5 V.
This should also be connected back to the
return path for the loop battery, LGND and relay drive ground RLYGND.
Negative supply rail, -5 V.
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 2 W to 4 W conversion,
constant current feed, ringing and ring trip detection, current limiting, switch hook indication and line and network
balance impedance setting using minimal external 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 VRIN, and converting it 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 and should be a.c. coupled to Vx which is the output from
the SLIC to the analog switch or voice CODEC input.
Gain Control
It is possible to set the Transmit and Receive gains by the selection of the appropriate external components.
The gains can be calculated by the formulae:
2W to 4W gain:
Gain 2 - 4 = 20*Log [ R13 / R12]
4W to 2W gain:
Gain 4 - 2 = 20*Log [0.891 * (R14 / R15)]
3
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
