MITEL MH88631-1, MH88631-2 Datasheet

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MH88631

Central Office Interface (LS/GS)

Preliminary Info rm atio n

Features

• Transformerle ss 2-4 w ire conv ersi on

• Line state dete ction outp uts

• - forward current

• - reverse current

• - ring ground

• - tip ground

• - ringing voltage

• Programmable audio transmit and receive gain

• Loop start or gro und s tart term inati on

• Selectable 600Ω or AT&T compromise ba lanc e
network

• -1 version: 20Hz Ringing Voltage

• -2 version: 50Hz Ringing Voltage

Applications

• PBX

• Channel b ank

• Intercom

• Key System

ISSUE 4 April 1995

Ordering Information

MH88631 -1 40 Pin S IL Pa ckag e
MH88631 -2 40 Pin S IL Pa ckag e

0°C to 70°C

Description

The Mitel MH88631-1, 2 Central Office Trunk
Interface circuit provides a complete audio and
signalling link between audio switching equipment
and a central office. The loop seize circuitry is
controlled by an external input to provide either a
loop start of ground start termination. The device is
fabricated using thick film ceramic technology to
achieve high density circuit design.

T
R

VTR+

VTR­RXIN­RXIN+

RG FC

Signal Detection

Active

Termination

QB QE XA XB XC VDD

RV

Circuitry

RC

TG

LPGND RINGND

Ground

Network
Balance

Figure 1 - Functiona l Block Dia gram

Ring

VEE

Audio Section

RXOUT

VCC+

VCC- AGND

Driver 1

Driver 2

Circuitry

(2-4 Wire)

TXIN+ TXIN-

Relay

Relay

RC1
RD1

RGND
CD

RD2
RC2

NETBAL
GSX

VX
VR
GSR

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MH88631 Preliminary Information

LPGND

VDD

RINGND

T
R

VTR-

VTR+

XC

XA

QE
AGND
RXIN+

RXIN-

VEE

TG
RC
RV

FC
RG
QB

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

XB

VEE

VDD

RXOUT

VCC+

GSR

TXIN-

VCC­TXIN+
AGND

VR

VX

RGND

GSX

RC1

NETBAL

RD1

CD
RD2
RC2

Figure 2 - Pin Connections

Pin Description

Pin #

1LPGNDLoop Ground is the system ground reference with respect to -48V.
2VDDPositive Po wer Supply (+5V).

Name Description

21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

3 RINGND

Ring Ground (Input). For Ground Start Trunk only a logic low input will enable the trunk
circuit to ground the Ring lead through a low resistance (390Ω). This is a signal to the C.O.

that the interface is seizing the line.
4TTip (Inp u t). Normall y connects to the “Tip” lead of the C.O.
5RRing (Input). Normally connects to the “Ring” lead of the C.O.
6 VTR- Connects to the TXIN+ (Pin 29) via an external capacitor (C1).
7 VTR+ Connects to the collector of an external transistor (Q1) and TXIN- (Pin 27) via an external

capacitor (C4)
8 XC External relay contact (K1) connecti on from XB (Pin 21), activates by loop seize control

input (RC1).
9 XA E xternal relay con tact (K1) connecti on from VTR+ (Pi n 7), activated by loop sei ze control

input (RC1).

10 QE Connects to the emitter of an external transistor (Q1).
11 AGND Analog Grou nd.
12 RXIN+ Differential Receive (Input). Connects to analog ground via an external capacitor (C2).
13 RXIN- Differential Receive (Input). Connects to RXOUT (Pin 24) via an external capacitor (C3).
14 VEE Negative Po wer S up ply. (-5V).

15 TG

Tip Lead Ground Detect (Ou tpu t). Active low.

16 RC Reverse Loop Current Detect (Outpu t). Active low .
17 RV Ringing Voltage Detect (Output). Active low.
18 FC

Forward Loop Curre nt Detect (Outpu t). Active low

19 RG Ring Lead detect (Output). Active low.
20 QB Connects to the base of an external transistor (Q1).

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Preliminary Information MH88631

Pin Description (Continued)

Pin #

21 XB External relay contact (K1) connection from XC (Pin 8), activated by loop seize control input

22 VEE Negative Po wer S up ply. (-5V).
23 VDD Po siti ve Power Sup ply. (+5V)
24 RXOUT Audio receive signal (outpu t) tothe RX IN- (Pi n 13), via an external decoupling capacitor

25 VCC+ Positive analog Power S up ply Voltage. (+12V).
26 GSR Gain Setting Rec eive (Input). Normally used to set the receive gain with an external

27 TXIN- Transmit (Input). Differe ntial audio signa l from VTR- (Pin 6), via an external capacitor

28 VCC- Negative Analog Power S upp ly Voltage. (-12V).
29 T XIN+ Transmit (Input). Differential audio signal from VTR- (Pin 6), via an external decoupling

30 AG ND An al og Gr ound.
31 VR Audio Receive (In pu t). The four-wire audio signal input to the interface .
32 VX Audio Transmit (Output). The four-wire audio signal output from the interfa ce.

Name Description

(RC1).

(C3).

resistor connected to RXOUT (Pin 24).

(C4).

capacitor (C1).

33 RGND Relay Grou nd.
34 GSX Gain Setti ng Transmit (Input). Normally used to set the transmit gain with an external

resistor connected to VX (Pin 32).

35 RC1 R e lay Co ntro l 1 (Input). A logic high will activate the relay (K1) to provid e loop seize

across Tip and Ring.

36

37

38

39 RD2 R e lay Dri ver 2 (Output). Op en collect or sinks current when RC2 is high. Diode clam p

40 RC2 R e lay Dri ver 2 (In put). A logic high will activate the relay (K2) to provide proper biasing to

NETBAL Network Balance (Input). When there is no connection (open), the network is balanced at

600Ω. When the pin is grounded, the network is balanced at AT&T compromise.

RD1 Relay Dri ver 1 (Outp ut). Open collect or sinks curren t when RC1 is high. Diode clamp

protecte d.

CD Clamping Diode. Normally connects to the po sitive supply voltage.

protecte d.

the Tip and Ring. This input control is used for Ground Start Trunk only.

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