MITEL MH88614 Datasheet

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MH88614

Programmable CODEC SLIC

Advance Information

Features

• Transformerless 2 -wire to 4- wire con versi on

• Battery Feed

• Ringing & M ess agin g Facil ity

• Power Down with Wake Up output

• Automat ic Ring Trip

• Programmable Constant Current

• Earth Grou nd B utton d etecti on

• Switch Hook detectio n

• Interface for a p rog ramm able CODE C

• Ring g roun d over-current protec tion

• Impedan ce reflec tion

• Loop Leng th Indi cati on

Applications

Line Interfac e for

• PABX

• Intercoms

• Key Telephone Syst ems

• Control S ystem s

ISSUE 2 April 1995

Ordering Information

MH88614 30 Pin SIL Package

0°C to 70°C

Descript io n

The SLIC provides a complete interface between an industry standard programmable CODEC or DSP and a subscriber loop.

Functions provided include battery feed, zero crossing ring control, programmable current feed, power down with wake up signal, cadenced messaging facility, switch hook & dial pulse detection, loop length indication and the capability of reflecting a programmable CODEC’s impedance or supplying a standard 600 ohm impedance to the line. The device is fabricated as a thick film hybrid using various technologies for optimum circuit design high reliability.

VX VR

Loop

SHK EGB

LCA

MSE

2W-4W

Converter

Loop

Supervision

Constant

Current Control

Switch

Circuits

MSG

RNGVEEVDD

BAT

Figure 1 - Functional Block Diagram

Line Drivers

Battery Feed

GND

TIP

RING

GND

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MH88614 Advance Information

IC IC

TIP

RING

LOOP

BGND

EGB

VBAT

AGND

VDD

VEE

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15

16 17

19 20

Figure 2 - Pin Connections

Pin Description

Pin # Name Descrip tio n

1ICInternal Connection 2ICInternal Connection

LCA

VRING

VMSE

MSE

SHK

21 22 23 24 25 26 27 28 29

3 TIP Connects to the “Tip” lead of the telephone line. 4ICInternal Connection 5 RING Connects to the “Ring” lead of the telephone line 6LOOPLoop Length Indication. The output on this pin is proportional to the loop lengt h /

resistance, and is valid for off hook conditions only.

7BGNDB a ttery Gro und . This pin is the re turn pin for the bat tery feed to the line and also for the

message voltage supply and the Ring Voltage supply. This pin should normally be connected to AGND.

8WUWake Up(Output). When in the power down mode this pin goes high to indicate the phone

has gone off hook. When this occurs the power down signal should be removed.

9EGB

Earth Ground Button Detection (Output) This output goes low when the ring lead or tip

lead is grounded. 10 IC Internal Connection 11 VBAT Battery Feed Supply. This pin is the supply for the line feed. (Typically -48V). 12 IC Internal Connection 13 PD

Power Do wn (In pu t) Applying a logic 0 (Active low) will Power down the hybrid. This may

be used, but must be removed to allow a call to be made or to reduce power consumption. 14 AGND Analog Ground. This pin is the return pin for th e positi ve and negati ve supplies and is

normally connected to BGND. 15 VDD Positive S upp ly. (Typically +5V). 16 VEE N egati ve Su pp ly. (Typically -5V). 17 IC Internal Connection 18 VR Receive (Input). The audio inpu t signal is applied to this pin from the programmable

CODEC. This signal is internally a.c. coupled

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Advance Information MH88614

Pin Description- (Continued)

Pin # Name Description

19 IC Internal Connection 20 VX Transmit (Output). The audio output signal appears on this pin and is internally a.c.

coupled. This signal is applied to the progra mmable CODE C . 21 IC Internal Connection 22 LCA L oo p Curr ent Adj ust (in pu t). The circuit has two constant current settings that are logic

selectable 23 IC Internal Connection 24 LA

25 IC Internal Connection 26 VRING Ring Voltage Supply. This pin is the supply for the Ringing signal to the telephone.

27 VMSE M essa ge Voltage Supply. This pin is the supply for the messag e signal to the telep hone.

28 RE Ring Enable (Input). The ringing signal is applied across Tip & Ring by applying a logic 1 to

29 MSE Message Signal Enable (Input). A cadenced signal can be applied to this pin which will

30 SHK

Functional Description

The MH88614 is an ONS SLIC for use with a programmable / intelligent CODEC or DSP. The SLIC performs all of the normal interface functions between the CODEC and the analog telephone set whilst having such additional features as Earth Ground Button Detection, message switching and Ringing switching with zero crossing.

Loop Alarm (Output) When the loop impedance exceeds the maximum limits that the SLIC

can support for a specified voltage & current this output will go low. This indicates that the

SLIC will no longer support the lin e. Note: Th is pin will also pulse low if Loop Disconnect

Dialling is perform ed, and goes low when the phone is on hoo k.

(Typically 90V

(Typically -100V)

this pin while the phone is “On Hook”. Ringing will be automatically stoppe d when the

phone goes “Off Hook” regardless of the state of the RE pin.

switch the V

prevent bell tinkle on the telephone. This is automatically switched off when the phone goes

off hook.

Switch Hook (Output). The outp ut of this pin goes low when the phone goes “O ff Hook”

and can be used externally to switch MSE off.

on -48V battery).

RMS

voltage onto Tip & Ring. The output voltage is internally conditioned to

MSG

Loop Supervision

The Loop Supervision circuit monitors the state of the phone line and provides three different output stages.

When the phone goes “Off Hook” the SHK low to indicate this state. This pin reverts to a high state when the phone goes back “On Hook” (see figure 3).

pin goes

The MH88614 is available as a 30 pin SIL package to increase board densities.

2 Wire to 4 Wire C onversi on

The hybrid performs 2 wire to 4 wire conversion by taking the 4 wire signal from the programmable CODEC at VR and converting it to a 2 wire differential signal at Tip & Ring. The 2 wire signal applied across Tip & Ring by the phone is converted to 4 wire signal at Vx which is the output from the SLIC to the programmable CODEC. Both the VR input & Vx output are internally a.c. coupled.

When the phone is off hook the circuitry can also detect two other features of the line status namely Earth Ground Button & Loop Alarm.

A logic low signal on the Earth Ground Button output indicates t hat an earth ground path has been applied to the Tip or Ring lead of the telephone. This function can be used for recall operations on phone sets with Earth Ground Buttons.

The Loop Alarm signal low to indicate that the R has been exceeded and that the circuit will no longer support the line.

Loop

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