MT91600

Data Sheet

3

Zarlink Semiconductor Inc.

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)]

16

Z2

Line Impedance Node 2. This is the common connection node between Z1 and Z3.

17

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.

18

X1

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.

19

VX

Transmit Audio (Output). This is the 4 W analog signal to the SLIC.

20

X3

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

21

VR

Receive Audio (Input). This is the 4 W analog signal to the SLIC.

22

X2

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.

23

C1

A filter capacitor for ring trip is connected between this pin and GND.

24

SHK

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.

25

RLYC

Relay Control (Input). An active high on this pin will switch RLYD low.

26

RLYD

Inverted Output of RLYC. It is used to drive the bipolar transistor that drives the relay

(see Figure 5.)

27

GND

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.

28

VEE

Negative supply rail, -5 V.

Pin Description (continued)

Pin #

Name

Description