Datasheet MH88422-2 Datasheet (MITEL)



MH88422

Line Interface Circuit

Preliminary Information

Features

• FAX and Modem interf ace (V29/V2 2 bis)

• Variants mat ch Germ an, UK & 600

Ω network

impedance s

• Provides reinforced barrier to interna tional PTT requiremen ts

• Transformerless 2-4 W ire conversion

• Loop star t oper ation

• Pulse and DT MF operati on

• Accommo date s extern al mo nitor ph one

• Line state dete ction out put s:

• -l oop curr ent/ri nging outp uts

• Single +5V operat ion, l ow idle po wer (5 mW)

• Full Duplex

• Suitable for p ower dow n ap plica tions

Applications

Interface to Central Office for:

•DAA

• Modem

•FAX

• Answering M achi ne

• Terminal Equip men t

ISSUE 5 April 1995

Ordering Information

MH88422 -1 14 Pin DIL Pa ckage MH88422 -2 14 Pin DIL Packag e MH88422 -3 14 Pin DIL Packag e

Surface Mount Options are available by adding the

Suffix “S”

Description

The Mitel MH88422 Line Interface Circuit provides a complete audio and signalling link between audio equipment and central office. The functions provided by the MH88422 include 2-4 Wire conversion, loop seizure, ring voltage and loop current detection. The device is fabricated as thick film hybrid which incorporates various technologies for optimum circuit design, high voltage isolation and very high reliability.

Variants are provided to meet German (-1) and UK (-3) line impedance (see section on Line Impedances), as well as a 600Ω variants (-2).

Isolation Barrier

Power

Supply

Opto-

TIP

RING

Active

Termina tio n

TXIN

TF

RLS

Audio Input

Buffer

Input Buffer

NETWORK CONNECTIONS

Isolation

Opto-

Isolation

Opto-

Isolation

Opto-

Isolation

Logic Input

Buffer

Audio

Buffer

Audio Buffer

Loop

Ring &

Buffer

USER CONNECTIONS

Transhybrid

Loss

Cancellat io n

Circuit

VDD AGND

LC

VR

VX

RVLC

Figure 1 - Functional Block Diagram

2-21

MH88422 Preliminary Information

VDD

AGND

LC

RVLC

NC

VX

VR

1 2 3 4 5

6 78

14

TIP

13

RLS

12

NC

11

TF

10

TXIN RING

9

NC

Figure 2 - Pin Connections

Pin Description

Pin # Name Description

1VDDPositive Pow er Su pp ly Voltage. +5V. 2AGNDAnalog Ground. 4-Wire Ground. Normally connect ed to System Ground. 3LC

4RVLCRin g Voltage and Current Detect (Output). A logic low indicates that loop current is

Loop Control (Input). A logic low activates internal circuitr y which provides a dc termination across Tip and Ring. Used for seizing the line and dial pulsing.

detected. The loop current can be due to the external monitor phone or the MH88422 in the off-hook mode. The RVLC output pulses when the external monitor phone is dial pulsing or when the MH88422 is dial pulsing via the LC

input. In addition, when the MH88422 is on the on-hook mode, a pulsing output indicates ringing voltage across the Tip and Ring leads. The pulsing output frequency is twice the ringing frequency.

5NCNo Connection should be mad e to this pin. 6VXTransmit (Outp u t). 4-Wire ground (AGND) referenced audio out put , biased at 2.5V.

Outputs in off-hook mode only.

7VRRecei ve (In pu t). 4-Wire ground (AG ND) referenced audio input, biased at 2.5V. LC

must be activated low and loop current must be flowing .

8NCNo Connection should be mad e to this pin. 9 RING Ring Lead. Connects to the “Ring” lead of the central office through an opt iona l relay

contact. The central office “Tip” and “Ring” leads may be interchanged.

10 TXIN Transmit (Input). Connects to the “Ring” lead of the central offi ce through a coupli ng

capacitor.

11 TF Tip Feed. Connects to the “Tip” lead of the central office through an internal resistor and

an optional external resistor.

12 NC No Connection sho uld be mad e to this pin. 13 RLS Ring Loop Sense (Input). Sense node for ringing voltage detector and the loop current

detector.

14 TIP Tip Lead. Connects to the “Tip” lead of the central office through an opti onal relay

contact. The central office “Tip” and “Ring” leads may be interchanged.

2-22

Preliminary Information MH88422

Functional Description

The MH88422 Line Interface Circuit is a COIC (Central Office Interface Circuit) used to interface FAX’s Modems or user defined equipment to Central Office 2-Wire Analog Trunks.

Opto-Isolation

The isolation barrier is designed to meet regulatory requirements for a reinforced barrier of 3kVac. It provides full isolation of mains voltages up to 250V RMS and all telecom voltages.

In order that this barrier is not bypassed a creepage/ clearance distance of 6.4mm minimum must be maintained between wiring, pcb tracking, etc., connected to external circuitry on either side of the barrier. To make this requirement simpler, pins on the MH88422 connected to opposite sides of the barrier are on opposite sides of the package.

External Protection Circuit

The RVLC outputs pulses when the external monitor phone is dial pulsing or when the MH88422 is dial pulsing via the LC

In addition, when the MH88422 is on-hook, a pulsing output indicates that ringing voltage is across the tip and ring leads; the pulsing output frequency is twice the ringing frequency. See Figure 3.

Ringing frequency may require external validation. An RC monostable is usually satisfactory for this purpose or this may also be achieved using software applications.

mode.

2-4 Wire Conversion

The 2-4 Wire conversion circuit converts the balanced full duplex signal at Tip and Ring of the central office line into a transmit ground referenced signal at VX (Transmit) of the MH88422. It also converts the receive ground referenced signal at VR (Receive) of the MH88422 into a balanced transmit signal at Tip and Ring of the central office line.

To meet regulatory high voltage requirement, an external protection circuit is required. The protection circuit shown in Figure 3 (Clamp Diode D1) is recommended.

DC Loop Termination

The DC loop termination circuitry provides the loop with an active DC load termination when a logic low is applied to the LC termination is similar to a resistance of approximately 300Ω (loop current dependent). Internal optically isolated circuitry is used to switch the termination in and out the loop. This is used for both seizing the line as well as generating dial pulses. The MH88422 will not seize the line when powered down.

(Loop Control) input. The

Supervision Features

The supervision circuitry is capable of detecting ringing voltage and loop current as well as the status of an optional external monitor phone. The RVLC (Ring Voltage Loop Current Detect) output provides a logic low when loop current flows due to the external monitor phone or the MH88422 being in the off-hook m ode .

In full duplex transmission, the Tip-Ring signal consists of an audio signal from the central office as well as an audio signal due to the VR input. There is an internal cancellation circuit which prevents the V signal appearing at the VX output. The degree to which the 2-4 wire conver sion circuit min imizes the contribution of the VR signal at the VX output is specified as transhybrid loss (THL).

The MH88422 is suitable to drive a COMBO II codec or a VLSI modem device.

Line Impedance

The MH88422 provides a fixed Tip-ring impedance which conforms to the following PTT requirements.

MH88422-1 Zin = 200 + 820 // 115nF

Germany

MH88422-2 Zin = 600Ω

MH88422-3 Zin = 370 + 620 // 310nF

UK

R

2-23

MH88422 Preliminary Information

Absolute Maximum Ratings* - All voltages are with respect to AGND unless otherwise specified.

Parameter Symbol Min Max Units

.

1 DC Supply Voltage V 2 Storage Temperature T 3 DC Loop Voltage V 4 Ringing Voltage V 5 Loop Current I

* Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied

DD

S

Bat

R

Loop

Recommended Operating Conditions.

Parameters Sym Min Typ

1 DC Supply Voltages V 2 Operating Temperature T 3 Ringing Voltage V

‡ Typical figures are at 25°C with nom inal +5V sup ply and are for design aid only

DD

OP

R

4.5 5.0 5.5 V 070°C

‡

Max Units Test Conditions

75 V

Loop Electrical Characteristics*

‡

Characteristics Sym Min Typ

1

Ringing Voltage No Detect

-1 Variant only Detect Ringing Voltage No Detect

All other Variants Detect

2

Ringing Frequency 15 68 Hz

VR

27

VR

14

Max Units Test Conditions

20 V

7V

V

RMS RMS

-0.3 6 V

-55 +80 °C

-100 +100 V

- 120 V

-90

V

RMS

Bat

=-48V

Refer to FT2 1TR2 for test method

Externally Adjustable

RMS

mA

3

On-Hook 2-wire Impedance 40k Ω 1kHz

4

Operating Loop Current 15 80 mA

5

Operating Loop Resista nce 2800 Ω V

6

Off-Hook DC -1 Variant Voltage

-2 Variant

-3 Variant

7

Leakage Current (2-Wire to AGND) 10 µ A 100V

8

Leakage Current on Hook

6.0

4.0

6.0

9.6 15

6.0

7.8

9.0

12.5

V V V V V V

910µAV

(Tip to Ring)

9

DC Resistance during dialling

-1 variant only 200 220 Ω I

10

Dial Pulse Distort ion ON

-1 Variant OFF All other Variant

* Loop Electrical Characteristics are over recommended operating conditions unless otherwise stated. ‡ Typical figures are at 25°C and are for desi gn aid only. Note 1: All of the above characteristics use a test circuit as per Figure 3.

0

+6

0

+2 +8 +2

+4

+10

+4

ms ms ms

=-48V, I

Bat

=25mA

I

Loop

=42mA

I

Loop

=15-20mA

I

Loop

=26mA

I

Loop

=25mA

I

Loop

=42mA

I

Loop

=-50V

Bat

=20-40mA

Loop

DC

Loop

=15mA

2-24

Preliminary Information MH88422

DC Electrical Characteristics†

Characteristics Sym Min Typ

‡

Max Units Test Conditions

1 2 Power Consumption PC 15 mW V 3 Low Level Output Voltage

RVLC LC

4 Low Level Input Voltage 5

† DC Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated. ‡ Typical figures are at 25°C with nominal+

Supply Current I

High Level Output Voltage

High Level Input Voltage Low Level Input Current High Level Input Current

5V supplies and are for design aid only.

DD

V

OL

V

OH

V

I

IH

I

IL

2.4

IL

2.0

IH

3mAV

0.4 V V

0.8

V

60

µΑµAV

60

= -5.0V, Idle state

DD

= -5.0V, Idle state

DD

I

= 4mA

OL

= 0.4mA

I

OH

= 5.0V

IH

= 0.0V

V

IL

AC Electrical Characteristics† - MH88422 All Variants

Characteristi cs Sym Min Typ

1 Input Impedance VR 47k Ω 2 Output Impedance at VX 3 Receive Gain (VR to 2-wire)

40

Frequency Response Gain (relative to Gain @ 1kHz)

‡

Max Units Test Conditions

10 Ω

3.5 dB Input 0.5V at 1kHz

dB

0

dB

300 Hz 3400 Hz

5 Signal Output Overload Level

at 2-Wire

6 Total Harmonic Distortion

at 2-wire

7 Power Supply Reject Ratio

at 2-wire

at VX

+2.0 +3.0 dBm V

+2.0 +3.0 dBm

THD

PSRR

1.2

30 30

% %

dB dB

5% @ 1kHz

THD <

=15 to 40mA

I

Loop

=4.5V to 5.5V

DD

Input -10dB at 1 kHz DC loop = 25mA

=5.0V

V

DD

Ripple 0.1V,1kHz on V

DD

8 Transhybrid Loss THL 20 dB Input -3.5dBm, 1kHz at

V

R

† Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated. ‡ Typical figures are at 25°C and are for design aid only.

Note 1: All of the above characteristics use a test circuit as per Figure 3. Note 2: All of the above test conditions use a test source impedance which matches the device’s impedance. Note 3: dBm is referenced to 600Ω unless otherwise stated.

2-25

MH88422 Preliminary Information

AC Electrical Characteristics† - MH88422-1

Characteris tics Sym M in Typ

‡

Max Units Test Conditions

1 2-Wire input Impedance

Zin 900 Ω @ 1kHz

(200Ω + 8 20 Ω //115nF)

2 Retu rn Loss at 2-Wire

(200Ω + 8 20 Ω //115nF)

3 Longit udi nal to Meta llic Ba lance 40

4 Idle Channel Noise

at 2-Wire

At VX

RL 20

20 20

55 53

Nc

22 24 26

65 60 60

-72

dB dB dB

-58 dBmp dBmp

300-500Hz 500-2500Hz 2500-3400Hz

50-300Hz 300-1000Hz 1000-4000Hz

5 Transmit Gain (2-Wire to VX) -0.4 dB Input 0.5V @ 1kHz

Off -Hook

6 Frequen cy Response Gain

(relative to gain @ 1kHz)

† Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated. ‡ Typical figures are at 25°C and are for design aid only.

-0.6

dB dB

300Hz 3400Hz

AC Electrical Characteristics† - MH88422-2

‡

Characteristi cs Sym Min Typ

Max Units Test Conditions

1 2-Wire Input Impedance

ZIn 600 Ω @ 1kHz

(600Ω)

2 Return Loss at 2-Wire

(Reference 600Ω )

3 Longitudinal to Metallic Balance

Metallic to Longitudinal Balance

4 Idle Channel Noise

at 2-Wire

at VX

ERL

SFRL2014

58 53 60 40

Nc

20 18

60 55

13 13

dB 500-2500Hz

dB dB dB dB

20 dBrnC

dBrnC

200-3200Hz 200-1000Hz

1k-3kHz 200-1000Hz 1k-4kHz

5 Transmit Gain (2-Wire to Vx) -0.4 dB Input 0.5V @ 1kHz

Off- Hook

6 Frequency Response Gain

(relative to gain @ 1kHz)

† Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated. ‡ Typical figures are at 25°C and are for design aid only.

-0.6

dB dB

200Hz 3400Hz

2-26

Preliminary Information MH89770

AC Electrical Characteristics† - MH88422-3

Characteristics Sym Min Typ‡Max Units Test Conditions

1 2-Wire In put I mpe dance

(370Ω + 6 20 Ω // 310nF)

2 Retu rn Loss at 2-Wire

(370Ω + 6 20 Ω // 310nF) 3 Longit udi nal to Meta llic Balance 50 60 dB 300-3400Hz 4 Idle Channel Noise

at 2-Wire

at VX

5 Transmit Gain (2-Wire to Vx) -0.4 dB Input 0.5V @ 1kHz

6 Freque n cy Gain

(relative to gain @ 1kHz)

† AC Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated. ‡ Typical figures are at 25°C and are for design aid only.

Note 1: All of the above characteristics use a test circuit as per Figure 3. Note 2: All of the above test conditions use a test source impedance which matches the device’s impedance. Note 3: dBm is referenced to 600Ω unless otherwise stated.

TIP-RING Drive Circuit

The audio input ground (AGND) referenced signal at VR, biased at 2.5V, is converted to a balanced output signal at Tip-Ring. 2-4 wire isolation is achieved through the use of optocouplers when the LC activated, low, and loop current flowing.

Zin 700 Ω @ 1kHz

RL 18 20 dB 200-2400Hz

Nc

-80

-0.6

The output impedance of the VX output is about 10Ω, therefore, with two external 1kΩ resistors configured as per Figure 5, this will result in 6dB of attenuation fo r a total gain of -6.4dB. For cor rec t gai n, t he M H8 842 2 input impedance must match the line impedance.

input is

-70

-68

dBmp dBmp

dB dB

Off-Hook 300Hz

3400Hz

Receive G ain

TIP-RING Receive Circuit

The differential audio signal at Tip-Ring is converted to

a ground (AGND) referenced si gnal, bia sed at 2. 5V, at the VX output. 2-4 Wire isolat ion is achieved through the use of o ptocouplers. The receive circuit operated when LC

is low and loop current is flowing

Transmit Ga in

Transmit Gain (Tip-Ring to VX) is fixed as indicat ed in “AC Electrical Characteristics”.

However, by adding external resistors to the VX output, the Transmit Gain can be reduced as shown in Figure 5. To limit the output current drawn, the minimum recomm ended resista nce to ground is 2kΩ.

Overall Transmit Gain =

-0.4 dB + 20log (R4 / (R4 + R3))

Receive Gain (VR to Tip-Ring) is fixed as indicated in “AC Electrical Cha ra c te ristics”. Howeve r, by adding a single external resistor in series with the VR input, the Receive Gain can be reduced.

Overall Receive Gain =

3.5dB + 20log (47kΩ /(47kΩ + Rext),

The input impedance of the VR input is 47kΩ, therefore, an external 100kΩ resistor in series with this input will result in 10dB of attenuation for a total gain of - 6. 5d B.

For correct gain, the MH88422 input impedance must match the line impedance.

2-27

MH88422 Preliminary Information

TIP

D1

RING

NOTES:

Calls are set up and cleared in this mode by the external controller. It turns on the loop via Loop Control, diallin g by pulsing loop control (or via

DTMF tones) and clearing down by turning Loop Control off.

VX

VR

RVLC

LC

6

7

4

3

Ring Voltage & Loop

Current Detect Output

Loop Control Input

C2

14

13

11

10

MH88422

TIP

RLS

TF

TXIN

9

RING

1

+5V

AGNDVDD

2

+

C1

1) C1: 10µF, 6V Ta ntalum

2) C2: 0.1µF, 250V (Typical Value)

3) D1: 180VDC Foldback Diode, e.g. TISP4180, TISP5180

4) VX and VR are biased at 2.5V, therefore, coupling capacitors

may be required depending on application.

Audio Output

Audio Input

Figure 3 - Typical Applicati on Circuit

14

R6

TIP

D1

RING

Line

Relay

Input

NOTES:

R2 & C2 form a dummy ringer, where R2 is on the hybrid and C2 must be fitted by the customer. To initate a manual call, lift the handset. The RVLC pin will indicat e that the line has been seize d by the monito r phone .

The required numbe r is then dialled and the connecti on s esta blishe d. Duri ng this phase the Loop Cont rol input should be turned ON to ensure that when the relay K1 is operated and the monitor phone removed from the line loop current is still maintained . On receipt of the corre ct progress tones the externa l control le r shoul d contro l the data tran smission and clear down the call when it is comp let ed by turn in g the Loop Con trol OFF. For applicatio ns in som e coun trie s su ch as Germany the MH88422 can not be used with an optional telephone but may still be used in a combined telephone/fax machine.

K1a

K1b

C2

K1

K1b

5) R6 adjust the monitor phone detect sensitivity typically set to 200 ohms for 5mA limit on the

-1 variant and 75 ohms on the -3 variant.

6) K1b is added to remove the dummy ringer when using a combined phone on the-1 variant and is not required for all other variants.

13

11

10

9

TIP

RLS

TF

RING

TXIN

MH88422

R2 Internal dummy Ringer Resistor

1

+5V

+

C1

3) D1: 180VDC Foldback Diode, e.g. TISP4180, TISP5180

4) VX and VR are biased at 2.5V, therefore , coup ling capa cito rs

may be required depe nd ing on ap plication.

RVLC

AGNDVDD

2

6

VX

7

VR

4

3

LC

1) C1: 10µF, 6V Tantalum

2) C2: 0.47µF, 100V

Ring Voltage & Loop

Current Detect Outpu t

Audio Output

Audio Input

Loop Control Input

2-28

Figure 4 - Typical Appl icati on Circu it wi th Dum my Ri ng er and M on ito r Phone

Preliminary Information MH88422

TIP

D1

RING

RECEIVE GAIN:

Audio input to Tip-Ring =20log(47k/(R5+47K))+3.5dB

= -6.5dB

TRANSMIT GAIN: Tip-Ring to Audio Output =20log(R4(R3+ R4))- 0.4dB

= -6.4dB

Note: The VX output gain has been reduced by 6dB (to -6.4dB) and the VR input gain has been

reduced by 9.9dB (to -6.4dB) in this example.

C2

14

13

10

R3

TIP

MH88422

RLS

11

TF

RVLC

TXIN

9

RING

VDD

1

+5V

1) C1: 10µF, 6V Tantalum

2) C2: 0.1µF, 250V (Typical Value)

180VDC Foldback Diode, e.g. TISP 4180 , TISP5 180

3) D1:

4) VX and VR are biased at 2.5V, therefor e, coup ling capacito r s may be required depending on application.

5) (R3+R4) should be > 2kΩ to prevent overload.

AGND

2

+

C1

VX

VR

LC

6

100k

7

R5

4

3

R4

Audio Output

Audio Input

Ring Voltage & Loop

Current Detect Output

Loop Control Input

Figure 5 - Typical App licati on Circuit for Gai n Adju stm ent

14

TIP

13

RLS

TIP

D1

RING

Meter

Pulse

Detector

Note:

Meter pulses at high frequency (16kHz or 12kHz) and high level (10V RMS) are used in some countries. The VX amplifier has a low pass filter which attenuates by typically 15dB at 16kHz (For the -1 variant). If this proves insufficient for specific applications, an LC reject filter is recommended.

C2

Meter Pulse Filter

11

10

TF

TXIN

9

RING

MH88422

1

+5V

VX

VR

RVLC

LC

AGNDVDD

2

+

C1

6

10µF

7

10µF

4

Current Detect Output

3

1) C1: 10µF, 6V Ta ntalum

2) C2: 0.1µF, 250V (Typical Value)

3) D1:180VDC Foldback Diode, e.g. TISP4180, TISP5 18 0.

Audio Output

Audio Input

Ring Voltage & Loop

Loop Control Input

Figure 6 - Typical Application Circui t with Meter Pul se Filter and Coup ling Capaci t or

2-29

MH88422 Preliminary Information

AAAA

A

AAA

AAAA

A

AAA

TIP

C2

D1

RING

Notes:

1) C1: 10µF, 6V Tantalum

2) C2:1.8µF, 250V (Normally in master socket)

3) D1:180VDC Foldback Diode , e.g. TISP418 0, TISP518 0

14

13

11

10

TIP

MH88422

RLS

TF

TXIN

9

RING

1

VDD

R2

RVLC

AGND

2

+

VX

VR

LC

6

7

4

Audio Output

Audio Input

Ring Voltage & Loop

Current Detect Output

3

Loop Control Input

C1

+5V

Figure 7 -Typical Application Circuit show in g UK Dumm y Ringe r Circu it.

0.27 Max

(6.9 Max)

0.08 Typ (2 Typ)

0.200+ (5.08+

Notes:

1) Not to sc ale

2) Dimensions in inches).

3) (Dimensions in millimetres). *Dim en si on s to ce ntre of pin.

0.010

0.25)

*

0.19 Max (4.8 Max)

0.020 + 0.005 (0.5 +

0.12)

0.10 Typ

(2.54 Typ)

0.063 Max(1.6 Min)

0.015 (6.6+0.4)

0.26+

1.42 Max

(36.1 Max)

1

AAA

AAAA

0.90 Typ

(22.9 Typ)

0.95 Max

(24.2 Max)

AAAA

AA

2-30

Figure 8 - Mechanical Data for 14 Pin DIL Hybrid

Preliminary Information MH88422

AAAA

A

AAA

AAAA

A

AAA

AA

0.19 Max

(4.8 Max)

0.063 Max (1.6 Max)

0.10 Typ

(2.54 Typ)

Notes:

1) Not to scale

2) Dimensions in inches).

3) (Dimensions in millimetres). *Dimensions to centre of pin.

*

0.20 + 0.005 (5.0 +

0.12)

*

0.20 + 0.010 (5.08 + 0.25)

0.08 Typ (2 Typ)

1.42 Max

(36.1 Max)

0.33 Max (8.4 Max)

1.08 Max

(27.4 Max)

AAAA

AA

0.060 Typ (1.52)

0.125+0.015±

0.38)

(3.18+

Figure 9 - Mechani cal Data for 14 Pin Surface M oun t Hybri d

0.1

(2.5)

0.89

(22.6)

0.04

(1.02)

0.16

(4.06)

Figure 10 - Recomme nde d Fo otpr int for 14 Pin Surface Mo un t Hybri d

2-31

MH88422 Preliminary Information

Notes:

2-32