MITEL MH88630 Datasheet

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MH88630

Central Office Interface (LS/GS)

Preliminary Information

Features

• Transformerless 2-4 W ire conversion

• Line state dete ction out put s:

- forward current

- reverse current

- ring ground

- tip ground

- ringing voltag e

• Programmable audio transmit and receive gain

• Loop start o r ground start termin ation

• Selectable 600Ω or AT&T comp romis e bala nce
network

Applications

• PBX Interface to Central Office

• Channel bank

• Intercom

• Key system

ISSUE 7 April 1995

Ordering Information

MH88630 40-Pin DIL Package

0°C to 70°C

Description

The Mitel MH88630 Central Office Trunk Interface
circuit provides a complete audio and signalling link
between an audio switching equipment and a central
office. The loop seize circuitry is controlled by an
external input to provide either a loop start or ground
start termination. The device is fabricated using thick
film hybrid technology to achieve high density circuit
design.

R

VTR+
VTR-

RXIN­RXIN+

VCC-

Relay

Driver 1

Relay

Driver 2

AGND

RC1
RD1
RGND
CD

RD2
RC2
NETBAL

GSX
VX
VR
GSR

FC

RG

T

Signal Detection

Termination

QB QE XA XB XC VDD VEE RXOUT TXIN+ TXIN-

Circuitry

Active

RCRV

LPGNDTG

RINGND

Ring

Ground

Network
Balance

VCC+

Audio Sec t ion

Circuitry

(2 - 4 Wire)

Figure 1 - Functional Block Diagram

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MH88630 Preliminary Information

IC

IC
IC

LPGND

RINGND

VTR+

QE
QB

VTR-

XA
XB

XC

RGND

RC1
RD1

CD

RD2
RC2

1
2

T

3

R

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

40
39

38
37
36

35
34
33
32
31
30
29
28
27
26
25
24
23
22
21

RG
FC
RV
RC
TG
VDD
VEE
AGND
RXIN­RXIN+
NETBAL
VX
GSX
TXIN+
TXIN­VCC­VCC+
RXOUT
GSR
VR

Figure 2 - Pin Connections

Pin Description

Pin # Name Description

1ICInternal Connection. Pin cut short. Leave open circuit .
2TTip (Input). Normally connects to the “Tip” lead of the C.O.
3RRing (Input ). Normally connects to the “Ring” lead of the C.O.
4ICInternal Connection. Leave open circuit.
5ICInternal Connection. Leave open circuit.
6 LPGND Loop Ground is the system ground reference with respect to -48 volts.

7 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 seizi ng the li ne.

8 VTR+ Connects to the coll ector of an external transist or (Q1) and TX IN - (pin 26) via an

external capacitor.

9 QE Connects to the emitter of an external tran sistor (Q1).
10 QB Connects to the base of an external transistor (Q1).
11 VTR- Connects to the TXIN+ (pin 27), via an external ca pacito r (C1).
12 XA External relay contact (K1) connection from VTR+ (pin 8), activated by loop seize control

input (RC1).

13 XB External relay contact (K1) connection from XC (pin 14), activated by loop seize control

input (RC1).

14 XC E xternal relay contact (K1 ) connection from XB (pin 13), activat ed by loop seize control

input (RC1).

15 RGND

Relay Gro und.

16 RC1 Relay Contr ol 1 (Input). A logic high will activate the relay (K1) to provide loop seize

across Tip and Ring.

17 RD1 Relay Driver 1 (Output): Open collector sinks current when RC1 is high. Diode clamp

protected.

18 CD Clamping Diode: Normally connects to the positive supply voltage.

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Preliminary Information MH88630

Pin Description (Contin ue d)

Pin # Name Description

19 RD2 Relay Driver 2 (Output): Open collector sinks current when RC2 is high. Diode clamp

protected.

20 RC2 Relay Contr ol 2 (Input): A logic high will activate the relay (K2) to provide proper

biasing to the tip and ring. This input control is used for Ground Start Trunk only.
21 VR Audio Receive (I nput). The 4-wire audio signal input to the interface.
22 GSR Gain Setting Receive (Input). Normally used to set the receive gain with an external

resistor connected to RXOUT (pin 23).
23 RXOUT Audio receive signal (output) to the RXIN- (pin 32), via an external decoupling capacitor

(C3).
24 VCC+ Positive analog P ow er Supp ly Voltage (+12V).
25 VCC- Negative analog Power Supply Voltage (-12V).
26 TXIN- Transmit (Input). Different audio signal from VTR+ (pin 8), via an external capacit or

(C4).
27 TXIN+ Transmit (Input). Different audio signal from VTR- (pin 11), via an external decoupling

capacitor (C1).
28 GSX Gain Setting Transmit (Input). Normall y used to set the transmit gain wit h an external

resistor connected to VX (pin 29).
29 VX Audio Transmit (Output). The 4-wire audio signal outp ut from the interf ac e.
30 NETBAL Network Balance (Input). When there is no connection (open), the network is balanced

at 600Ω. When this pin is grounded, the network is balanced at AT&T compromise.
31 RXIN+ Differential Receive (Input). Connects to analog ground via an external capacitor (C2).
32 RXIN- Differential Receive (Input). Connects to RXOUT (pin 23) via an external capacitor

(C3).
33 AGND Analog Gro und .
34 VEE Negative Power Supply (-5V).
35 V DD Positive Power Supply (+5V).

36 TG
37 RC
38 RV Ringing Voltage Detect (Output). Active low.
39 FC Forward Loop Current Detect (Output). Active low

40 RG

Tip Lead Ground Detect (Output). Active low.

Reverse Loop current Detect (Output). A ctive low.

Ring Lead Ground Detect (Outp ut). Active low.

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