MITEL MH88422-1, MH88422BD-1, MH88422-2, MH88422-3 Datasheet

MH88422

Data Access Arrangement

Preliminary Information

Features

• FAX and Modem interface (V29)

• Variants available with different line impedances

• Provides reinforced barrier to international PTT requirements

• Transformerless 2-4 Wire conversion.

• Integral Loop Switch

• Dial Pulse and DTMF operation

• Line state detection outputs

• Loop current/ringing outputs

• Single +5V operation, low on-hook power (5mW)

• Full duplex data transmission

Applications

Interface to Central Ofﬁce or PABX line for:

• Modem

•FAX

• Telemetr y

DS5067 ISSUE 10 November 1998

Ordering Informations

MH88422-1/2/3 26 Pin DIL Package MH88422BD-1 26 Pin DIL Package

0°C to 70°C

Description

The Mitel MH88422 Data Access Arrangement (D.A.A.) provides a complete interface between data transmission equipment and a telephone line. All functions are integrated into a single thick ﬁlm hybrid module which provides high voltage isolation, very high reliability and optimum circuit design needing a minimum of external components.

A number of variants are available to meet particular country impedance requirements. The D.A.A. has been designed to meet regulatory approvals requirements in these countries.

TIP

RING

TXIN

RLS

Input Buffer

Line Termination

Network Connections

Isolation Barrier

Opto-

Isolation

Opto-

Isolation

Opto-

Isolation

Opto-

Isolation

Logic Input

Buffer

Audio

Buffer

Audio Buffer

Ring & Loop

Buffer

User Connections

Figure 1 - Functional Block Diagram

Transhybrid

loss

cancellation

circuit

VDD

AGND

RVLC

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MH88422 Preliminary Information

VDD

AGND

RVLC

IC IC

IC/NP

1 2 3 4 5 6 7 8 9 10 11 12 13

26 25 24 23 22 21 20 19 18 17 16 15 14

TIP IC RLS IC/NP IC IC/NP TF NP TXIN IC RING NP IC

Figure 2 - Pin Connections

Pin Description

Pin # Name Description

1 VDD Positive Supply Voltage. +5V.

2, 4, 6,

8, 9

3 AGND Analog Ground. 4-Wire Ground. Normally connected to System Ground. 5 LC Loop Control (Input). A logic 0 activates internal circuitry which provides a line

IC Internal Connection. This pin is cropped short.

termination across Tip and Ring. Used for seizing the line and dial pulsing.

7 RVLC Ringing Voltage and Current Detect (Output). Indicates the status of loop current

and ringing voltage.

10, 12 IC/NP Internal Connection or No Pin Fitted. This pin is either cropped shor t or not ﬁtted,

depending on the variant. See Note 1 11 VX Transmit (Output). Analog output to modem/fax chip set. 13 VR Receive (Input). Analog input to modem/fax chip set.

14, 17 IC Internal Connection. This pin is cropped short. 15, 19 NP No Pin Fitted.

16 RING Ring Lead. Connects to the "Ring" lead of a telephone line. 18 TXIN Dummy Ringer Connection. Connects to the "Ring" lead of a telephone line through a

dummy ringer capacitor. 20 TF Tip Feed. Connects externally to the RLS pin.

21, 23 IC/NP Internal Connection or No Pin Fitted. This pin is either cropped shor t or not ﬁtted,

depending on the variant. See Note 1 24 RLS Ringing Loop Sense. Connects externally to the TF pin. 25 IC Internal Connection. This pin is cropped short. 26 TIP Tip Lead. Connects to the "Tip" lead of a telephone line.

Notes:

1. Variant 1, 4 BD-1 - pins 10,12, & 21 are cropped short. Pin 23 is not ﬁtted.

2. Variant 2 - pin 23 is cropped short. Pins 10, 12 & 21 are not ﬁtted.

3. Variant 3 - pins 12 and 21 are cropped short. Pins 10 and 23 are not ﬁtted.

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Preliminary Information MH88422

Functional Description

The device is a Data Access Arrangement (D.A.A.). It is used to correctly terminate a 2-Wire analog loop. It provides a signalling link and a 2-4 Wire line interface between an analog loop and the subscriber’s data transmission equipment such as Modems, Facsimiles (Fax’s), Remote Metering and Electronic Point of Sale equipment (EPOS).

Isolation Barrier

The device provides an isolation barrier implemented by using optocouplers. This is a reinforced barrier for an instantaneous power surge of up to 3kV r.m.s., for example a lightning strike. It also provides full isolation for a continuous AC voltage level of up to 250V r.m.s.

External Protection Circuit

Should the input voltage from the line exceed that isolated by the optocoupler, an External Protection Circuit assists in preventing damage to the device and the subscriber equipment. See Figure 3.

Input Impedance

The MH88422 is available in a number of different variants each of which has its own ﬁxed Tip-Ring AC input impedance (Zin). Each variant is identiﬁed by the ﬁnal digit in its part number, as listed below. Also shown are the countries whose PTT requirements match these impedances.

MH88422-1 Zin = 220Ω + 820Ω // 120nF Australia / South Africa / Spain

MH88422BD-1 Zin = 220Ω + 820Ω // 115nF German BABT ZV5

MH88422-2 Zin = 600Ω North America

MH88422-3 Zin = 370Ω + 620Ω // 310nF UK / New Zealand

Many of these countries now pass equipment approved to CTR21. The MH88422 will not meet this speciﬁcation. See the MH88437 datasheet for a CTR21 Product.

Line Termination

When Loop Control (LC) is at a logic 0, a line termination is applied across Tip and Ring. The device can be considered off-hook and DC loop current will ﬂow. The line termination consists of both a DC line termination and an AC input impedance.

When LC is at a logic 1, a Dummy Ringer is applied across Tip and Ring. The device can be considered on-hook and negligible DC current will ﬂow. The dummy ringer is an AC load, which represents a telephone’s mechanical ringer.

DC Line Termination

When LC is at a logic 0, an active termination is applied across Tip and Ring, at which time it can be considered to be in an off-hook state. This is used to terminate an incoming call, seize the line for an outgoing call, or if it is applied and disconnected at the required rate, can be used to generate dial pulses. This termination resembles approximately 300Ω resistance, which is loop current dependent.

Dummy Ringer

This device supports a dummy ringer option which can be conﬁgured by the inclusion of external components. Further details relating to component values and conﬁguration can be obtained from MSAN-154. For example, Figure 3 shows capacitor C2 which if set to 1.8µF would meet the New Zealand dummy ringer requirements.

2-4 Wire Conversion

The device converts the balanced 2-Wire input, presented by the line at Tip and Ring, to a ground referenced signal at VX, as required by modem/fax chip sets.

Conversely the device converts the ground referenced signal input at VR, to a balanced 2-Wire signal across Tip and Ring.

During full duplex transmission, the signal at Tip and Ring consists of both the signal from the device to the line and the signal from the line to the device. The signal input at VR, being sent to the line, must not appear at the output VX. In order to prevent this,

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MH88422 Preliminary Information

the device has an internal cancellation circuit. The measure of attenuation is Transhybrid Loss (THL).

The Transmit (VX) and Receive (VR) signals are ground referenced (AGND), and biased to 2.5V. The device must be in the off-hook condition for transmission or reception to take place.

Transmit Gain

The Transmit Gain of the MH88422 is the gain from the differential signal across Tip and Ring to the ground referenced signal at VX. The internal Transmit Gain of the device is ﬁxed and depends on the variant as shown in the AC Electrical Characteristics table. For the correct gain, the Input Impedance of the MH88422 variant used, must match the speciﬁed line impedance.

By adding an external potential divider to VX, it is possible to reduce the overall gain in the application. The output impedance of VX is approximately 10Ω and the minimum resistance from VX to ground should be 2kΩ.

Characteristics table. For the correct gain, the Input Impedance of the MH88422 variant used, must match the speciﬁed line impedance.

The input impedance to ground of VR is 47kΩ and this can be used with an external series resistor to form a potential divider and reduce the overall gain in the application.

Example: If R3 = 100kΩ, in Figure 3, the Gain would reduce by 3.0dB.

Supervisory Features

The device is capable of monitoring the line conditions across Tip and Ring, this is shown in Figure 3. The Ringing Voltage Loop Current detect pin (RVLC), indicates the status of the device. The RVLC output is at logic 0 when loop current ﬂows, indicating that the MH88422 is in an off hook state.

When the device is generating dial pulses, the RVLC pin outputs a TTL pulse at the same rate.

Example: If R1 = R2 = 2kΩ, in Figure 3, the gain would reduce by 6.0dB.

Receive Gain

The Receive Gain of the MH88422 is the gain from the ground referenced signal at VR to the differential signal across Tip and Ring. The internal Receive Gain of the device is ﬁxed as shown in the AC Electrical

MH88422

TIP

RLS

TXIN

RING

VDD

+5V

TIP

Protection

Circuit

RING

Notes:

1) R1, R2: Transmit Gain Resistors

2) R3: Receive Gain Resistor

3) C1: 10µF 6V Tantalum

4) C2: Dummy Ringer Capacitor 250V

5) C3, C4: 10µF AC coupling Capacitors

An AC ringing voltage across Tip and Ring will cause RVLC to output a TTL pulse at double the ringing frequency with an envelope determined by the ringing cadence.

Mechanical Data

See Figure 10, for details of the mechanical speciﬁcation.

AGND

RVLC

Ring Voltage & Loop

Current Detect Output

Loop Control Input

Audio

Output

Audio

Input

2-16

Figure 3 - Typical Application Circuit

Preliminary Information MH88422

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 - 2 variant

- all other variants

5 Loop Current I

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

BAT

Loop

-0.3 6 V

-55 +125 ˚C

-110 +110 V

-2

150 120

-90mA

Recommended Operating Conditions

Parameter Sym Min Typ‡Max Units Test Conditions

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

‡ Typical ﬁgures are at 25˚C with nominal +5V supply and are for design aid only

Loop Electrical Characteristics

†

4.75 5.0 5.25

02570˚C

75 90 Vrms 150 Vrms for -2 variant

Characteristics Sym Min Typ‡Max Units Test Conditions

Vrms Vrms

1 Ringing Voltage

-1 V ariant Only No Detect Detect

BD-1 V ariant Only No Detect Detect

All other V ariants No Detect Detect

2 Ringing Frequency

BD-1 Variant Only All other Variants

3 Operating Loop Current

BD-1 Variant Only All other Variants

4 Off-Hook DC Voltage

-1 Variant

-2 Variant

-3 Variant

23 15

20 15

6.0

2.4

3.1

6.0

28 68

80 80

28.8

6.0

7.8

9.0

14.0

Vrms Vrms

Hz Hz

mA mA

V V

V V V

V V

Externally Adjustable See MSAN-154

Test circuit as Fig 4 I

=19mA (See Note 1)

Loop

=60mA

Loop

=15mA

Loop

=20mA (See Note 2)

Loop

=26mA

Loop

=15mA (See Note 3)

Loop

=90mA

Loop

BD-1 Variant

6.0

10.8 27

=20mA (See Note 4)

Loop

=50mA

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