MITEL MH88600 Datasheet

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MH88600

Global SLIC

Preliminary Information

Features

• Programmable line impedance matching

• Internal complex i mp edance netw ork s

• Transformerless 2-4 wire conversion

• Programmable transmit/receive gain

• Accomm odat es worl dw ide trans miss ion standards

• Opera tes with a wide range of ba tte ry volt ages

• Adjustab le c onsta nt curre nt ba ttery feed

• Overvol tag e and sho rt circu it pro tectio n

• Switch hoo k an d groun d bu tton de tectio n

• Ring tri p filte r and rel ay d river

• Low pow er co nsump tion

• High power dissipation capability during fault conditions

Applications

Line interface for:

• PABXs

• Contr ol Sys tems

• Key Telephone Sy stems

• Central Office Equipment

ISSUE 7 April 1995

Ordering Information

MH88600 40 Pin DIL Hybrid

0°C to 70°C

Description

The MH88600 is a SLIC (Subscriber Line Interface Circuit) which provides all of the BORSCH functions of Battery Feed, Overvoltage Protection, Ringing Feed, Line Supervision and 2-4 Wire Hybrid conversion. In addition, the device matches the many different line impedances specified by regulatory authorities of around the world.

TF1 TF2

TIP

RING

RF1

RF2

Tip Drive

Over Voltage &

Short Circuit

Protection

Ring Drive

VREF

Constant

Current

Battery Feed

LCA

ZN14

Line Supervision

EGB

SHK

ZN13.................ZN8

Impedance Matchi ng Network

2-4 Wire

Hybrid Circuit

Ring Trip Filter

Relay Driver

ZN7.....................ZN1

Figure 1 - Functional Block Diagram

Gain Adjust

VRR

GNDA

VDD

ZN0

PG2

PG4

PG3 PG1

VEE

Vbat

GNDBat

2-83

MH88600 Preliminary Information

ZN14

39 38 37

36 35

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

ZN13 ZN12 ZN11 ZN10 ZN9 ZN8 ZN7 ZN6 ZN5 ZN4 ZN3 ZN2 ZN1 TX PG3 PG1 PG2 PG4 ZN0

Pin Description

TIP

RC RD

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

VBat

RF1 RF2

RING

GNDBat

TF2 TF1

GNDA

VEE VDD VRR

LCA

SHK

EGB VRef

Figure 2 - Pin Connections

Pin # Name Description

1 No pin at this location. 2V

Bat

Battery Supply Voltage (Negati ve).

3RF1Ring Fe e d ( 1 ): Conne ct to relay contact. See Figures 6 & 7. 4

RF2

Ring Fe e d ( 2 ). Connect to relay contact. See Figu res 6 & 7. 5 RING Connects to the “Ring” or “B” lead of the telephone line. 6 TIP Connects to the “Tip” or “A” lead of the telephone line. 7I/CInternal Connection . 8GND

Battery Supply Ground (Positive ): Connect to System Ground

Bat

9TF2Tip Feed (2). Connect to TF1 for unbalanced ringing, see Figure 6. Connect to relay

contact for balanced ringing, see Figure 7.

10 TF1 Tip Feed (1). Connect to TF2 for unbalanced ringing, see Figure 6. Connect to relay

contact for balanced ringing, see Figure 7.

11 GNDA Analog Ground: Normally connected to System Ground. 12 V 13 V 14 V

EE DD RR

Negative Power Supp ly Voltage: Normally -5V. Positive Pow er Su pp ly Voltage: Normally +5V. Ringing Relay Cl am p Di ode : Connect to relay coil and to relay supply voltage

(Positive). For +5V relay, connect to VDD. 15 RC Ring Control (Input): A logi c hig h will activat e the Ri ng Relay D rive if SHK is high. 16 RD

Ring Relay Drive (Outpu t ). Connect to relay coil. A logic low will activate the relay by

sinking current from VRR through the relay coil. 17 LCA Loop Current Adjust (Input): Loop current is prop ortio nal to the vol tage at this input.

Normally connected to VRef 18 SHK Switch Hook Detect (Output): A logic low indicates an off-hook condition. 19 EGB 20 V

2-84

Ref

Earth Ground Button (Output ): A logic low indicates a grounded Ring lea d condition.

Voltage Reference (Output): Normally connected to LCA for default loop current.

Preliminary Information MH88600

Pin Description (Contin ue d)

Pin # Name Description

ZN0

Impedance Node 0. Connect to external network for impedance (Zin) setting. See Table 2 and Figure 8.

22 PG4 Programming 4 (Input). Used for programmable gain and fo r default gain. Used as 4-

Wire Receive Input for default gain. See Table 3 and Figure 4 and 5.

23 PG2 Programming 2 (Input). U sed for programmab le gain. Used with resistor for 4-Wire

Receive Input. See Table 3 and Figure 4. 24 PG1 Programming 1 (Input). Used for programmable gain. See Table 3 and Figure 4. 25 PG3 Programming 3 (Input). Used for programmable gain and for default gain. See Table 3

and Figure 4 and 5. 26 TX 4-Wire Transmit Output: 27 ZN1 Impedance Node 1: Connect to other Impedance Nodes for impe dance (Z

see Table 1. Or , connect to external network for impedance (Z

) setting, see Table 2 and

) setting,

Figure 8. 28 ZN2 Impedance Node 2: Connect to other impedances Nodes for im pedance (Zin) setting.

See Table 1. 29 ZN3 Impedance Node 3: As per ZN2. S ee Table 1. 30 ZN4 Impedance Node 4: As per ZN2. S ee Table 1 31 ZN5 Impedance Node 5: As per ZN2. S ee Table 1 32 ZN6 Impedance Node 6: As per ZN2. S ee Table 1 33

ZN7

Impedance Nod e 7: As per ZN2. See Table 1 34 ZN8 Impedance Node 8: As per ZN2. S ee Table 1 35 ZN9 Impedance Node 9: As per ZN2. S ee Table 1 36 ZN10 Impedance Nod e 1 0: As per ZN2. See Table 1 37 ZN11 Impedance Nod e 11: As per ZN2. See Table 1 38 ZN12 Impedance Nod e 1 2: As per ZN2. See Table 1 39 ZN13 Impedance Nod e 1 3: As per ZN2. See Table 1

40 ZN14 Imp eda nce Nod e 14 : Connect to external net work for impedance (Z

Table 2 and Figure 8.

) setting. See

2-85

MH88600 Preliminary Information

Functional Description

The BORSH Functions

The MH88600 performs all of the BORSH functions; Battery Feed, Overvoltage Protection, Ringing, Supervision and Hybrid.

Battery Feed

The MH88600 provides the loop with constant DC current to power the telephone set. The voltage (negative) applied at the LCA pin determines the magnitude of the lop current.

= 3.731 x VLCA mA (±2mA)

Loop

Either the internal (V voltage reference may be used to set the loop current.

Overvol tage P rote ction

The MH88600 is protected from short term (20ms) transients (+250V) between Tip and Ring, Tip and ground, and Ring and Ground. However, additional protection circuitry may be needed depending on the regulatory requirements which must be met. Normally, simple external shunt protection as shown in Figures 6,7 and 8 is all that is required.

Ringing

The MH88600 has the capability to accommodate both balanced and unbalanced ringing sources. Refer to Figure 7 for the Balanced Ringing Circuit and Figure 6 for the Unbalanced Ringing Circuit.

Supervision

The MH88600 is capable of detecting both Ground Button and Switch Hook conditions. The Ground Button detection (a logic low at the EGB operates when an imbalance in Tip and Ring DC current exceeds an internal threshold level caused by a grounded Ring Lead. Use of the EGB restricted to the off-hook condition of the telephone. The Switch Hook detection operates (a logic low at the SHK an interna l th reshold level .

output) when the DC loop current exceeds

) or an external negative

Ref

output)

output is

Hybrid

The 2-4 Wire Hybrid circuit separates the balanced full duplex signal at Tip and Ring of the telephone line into receive and transmit ground referenced signals at RX (receive) and TX (transmit) of the SLIC. The Hybrid also prevents the input signal at RX from appearing at TX. The degree to which the Hybrid prevents the RX signal from appearing at TX is specified at transhybrid loss.

Tip-Ring Drive Circuit

The audio input ground referenced signal at RX is converted to a balanced output signal at Tip and Ring. The output signal consists of the audio signal superimposed on the DC Battery Feed Constant Current. The Tip-Ring Drive Circuit is optimised for good 2-Wire longitudinal balance.

Short Circuit Protection

The MH88600 is protected from long term (infinite) short circuit conditions occurring between Tip and Ring, Tip and Ground, Ring and Ground, and Ring and Batte ry. The current is lim ited to the sam e v alue as the Constant Current Battery Feed.

Programmable Line Impedanc e

The MH88600’s Tip-Ring (Zin) impedance can be matched to the different impedances specified by different telephone administrations worldwide. This is accomplished by either linking specific pins as specified in Table 1, or by adding external components as shown in Figure 8 and Table 2.

Programmable Transmit & Receive G ain

Transmit gain (TX to Tip-Ring) and Receive Gain (Tip-Ri ng to RX) c an be prog ram med by conn ectin g external resistors as indicated in Figure 4 and Table

3. Alternatively, the default Receive Gain of -4d Band Transmit Gain of +4dB can be obtained by connecting pins as shown in figure 5 and Table3.

Note that RX is not a pin on the SLIC. The RX terminal will be either PG4 or the connection to the receive gain programming resistor RRX shown in Figure 4 and Figure 5.

The Ring Trip Detection Circuit prevents false offhook detection due to the current associated with the AC ringing voltage and also due to the large current transients when the ring voltage is switched in and out. In addition , th e circu it pr ev e nt s con ne c ti on of the ringing source during off-hook conditions.

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Preliminary Information MH88600

Loop Current (mA)

Loop Detect Threshold

Maximum Loop Length (Ω)

2000

VBat = -24V VBat =-48V

VBat = -24V

500

1000 1500

VBat = -48V

2000

Figure 3a - Loop Current vs.Maximum Loop Current

ILoop = 20mA

Maximum Loop Length (Ω)

1800

1600

1400

1200 1000

800

600

400

200

ILoop = 25mA

Figure 3b - Maxim um L oop L ength vs Batt ery vo ltag e

VBAT (V)

2-87

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