Datasheet MH88520-1 Datasheet (MITEL)

Features



MH88520-1

German Subscriber Line Interface Circuit (SLIC)

Preliminary Information

ISSUE 4 April 1995

• Differential to s ingle en ded conv ersion

• Transformerless 2-2 wire conversion

• Minim um in sta lla tio n s pa ce

• Off-Hook detection and LED

indic ato r d riv e

• Relay drive outp ut

• Battery and ri ngin g feed to line

• Logic interface: MUTE

, SHK, RRC

• Mute of inco ming aud io

• Dial pulse detection

• Voltage surge protecti on

• German compl ex inpu t impe da nce

Applications

Line Interfac e for:

• Intercoms

• Key System s

• PABX

Ordering Information

MH88520-1 20 Pin SIL Pa ckag e

0°C to 70°C

Descript io n

The Mitel MH88520-1 German Subscriber Line
Interface Circuit provides a complete interface
between the telephone line and a speech switch
requiring only single bidirectional switch per
crosspoint. The functions provided by the
MH88520-1 include bidirectional differential to single
ended conversion in the speech path, line battery
feed, ringing feed and loop and dial pulse detection.
The device is fabricated as a thick film hybrid in a
20-pin ‘single-in-line’ (SIL) package allowing
optimum circuit board packing density and very high
reliability.

TIP (A)

RING (B)

RING FEED 1

RING FEED 2

VRLY

RRD
RRC

RGND

Loop Feed/

Ring Feed

Relay Drive

Circuit

VBAT

AGND VDD VEE

Speech Circuit

Figure 1 - Functional Block Diagram

Loop Detectio n

JUNC

MUTE

SHK

LED

THRESH ADJ

2-63

MH88520-1 Preliminary Information

TIP

IC

RING

RF1

IC

RF2

IC

VEE
LED

THRESH ADJ

SHK

VDD

AGND

VBAT

MUTE

JUNC

RRD

RGND

RRC

VRLY

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

Figure 2 - Pin Connections

Pin Description

Pin # Name Description

1TIPTip Lead. Connects to the “Tip” lead (A-wire) of the telephone line.
2ICInternal Connec tion . Leave open circuit.
3 RING Ring Lead. Connects to the “Ring” lead (B-wi re) of the telephon e line.
4RF1Ring Fe ed 1. Connect to the Ring Relay contact. See Figure 5.
5ICInternal Connec tion . Leave open circuit.
6RF2Ring Fe ed 2. Connect to normall y closed contact of Ring Relay. See Figure 5.
7ICInternal Connec tion . Leave open circuit.
8V

EE

9LED

10 SHK

11 THRESH ADJ Allows adjustment of SHK
12 V

DD

Negative Pow er Su pp ly Voltage. Normally -5V.
LED Drive (Output). Drives an LED directly. A logic low indicates an off-hook condition.
Switch Hook Detect (Output). A logic low indicate s an off-hook and dial pulsing

condition. Open collector out put wit h 10k Ω internal pull up to V

DD

.

detection threshold as shown in Figure 6.

Positive Power Supply Voltage. Normally +5V. This provides current for both internal

circuitry as well as the loop.
13 AGND Analog Grou nd . Supply and Bat tery Ground.
14 V

BAT

15 MUTE

Battery Supply Voltage. Normally -24V. This provides current to the loop.

MUTE (Input). A logic low will mute signals coming from Tip-Ring to the JUNC pin.

16 JUNC JUNCTOR. Ground (AGND) referenced transmit and receive speech path.
17 RRD

Ring Relay Drive (Outpu t). Connects to the ring relay coil. A logic low activates the

relay.
18 RGND Relay Ground. Return path for relay supply voltage. Normally connected to AGND.
19 RRC Ring Relay Control (Input). A logic high activates the Ring Relay Drive (RRD

) outputs.

20 VRLY Relay Positive Supply voltage. Normally +5V. Connects to the relay coil and the relay

supply voltage. An internal clamp diode from VR LY to GRND is provided.

2-64

Preliminary Information MH88520-1

Functional Description

The BORSH Functions

The MH88520-1 performs all of the Borsh functions
of Battery Feed Overvoltage Protection, Ringing,
Supervision and Hybrid (2-2 Wire).

Return Loss at Tip-Ring

To maximise return loss, the impedance at Tip-Ring
should match the SLIC’s impedance (220R + 820R //
115nF). However, the SLIC’s input impedance is
dependent on the JUNCTOR termination resist ance.
Therefore the JUNCTOR must be terminated with
754Ω.

Figure 3 illustrates a typical connection between two
SLICs through two crosspoint switches. Optimum
return loss occurs when the JUNCTOR is terminated
with 754Ω. Since the JUNCTOR input/output
impedances is 604Ω and the crosspoint switch
resistances are 75Ω + 75Ω, this configuration gives
optimum return loss as shown in Figure 4.

Hybrid

The 2-2 wire hybrid circuit converts the incoming
balanced signal at Tip and Ring of the telephone line
into a ground referenced output signal at JUNC of

the SLIC, and converts the ground referenced input
signal at JUNC of the SLIC into the non-balanced
output signal at Tip-Ring of the telephone line.

Mute

A logic low at the MUTE input results in muted
signals coming from Tip and Ring to the JUNC
terminal while allowing signals from the JUNC
terminal to Tip and Ring to be transmitted.

Overvoltage Protection

The MH88520-1 is protected from short term (1ms)
(+250V) between Tip and Ring, Tip and Ground, and
Ring and Ground. However, additional protection
circuitry may be needed depending upon the
requirements which must be met for the final
equipment.

Loop Detection

The loop detection circuit determines whether a low
enough path is across Tip and Ring to be recognised
as an off-hook condition. (Threshold impedance =

5.4kΩ with no adjustment). This threshold level can
be adjusted by the use of external resistors as
shown in Figure 6. When an off-hook condition
occurs the SHK
low level. These outputs also toggle during incoming
dial pulses.

and LED outputs toggle to a logic

TIP

RING

TIP

RING

1

TIP

3

RING

MH88520-1

16

JUNC

75Ω

CROSSPOINT

SWITCH

SLIC 1

MH88520-1

1

TIP

8

RING

JUNC

16

SLIC 2

75Ω

CROSSPOINT

SWITCH

Figure 3 - SLIC Crosspoi nt S witc h Connecti on

2-65

MH88520-1 Preliminary Information

Ringing

The relay drive circuit switches ringing onto Ring
Feed (Fig. 7). The diode is present to suppress
voltage transients during relay switching caused by
the inductive coils of the relay. Ringing voltage
included ac ringing (90V

typically) and DC line

RMS

feed voltage (-24V typically).

Line Feed/Ring Feed Circuit

The line feed circuit provides loop current and the
ability to apply ringing onto Tip and Ring. The
impedance from Ring Feed to GND is 600Ω dc
(although for ac it is optimised for a German complex
impedance) which gives the loop current as:

Voltage at Ring Feed pin Amps

Telephone Impedan ce + 600

The positive supply for the line feed circuit is VDD
though the loop current is determined from Ring
Feed and GND.

Line Impedance

The MH88520-1’s Tip-Ring (Zin) impedance is fixed
at the Germ an co mp l ex i mp e dan ce . Fo r correct SLIC
impedance, JUNC must be appropriately terminated.

See AC Electrical Characteristics.

Transmit and Rece ive Ga in

Transmit Gain (JUNC to Tip-Ring) and Receive Gain
(Tip-Ring to JUNC) are fixed (See AC Electrical
Characteristics). For correct gain, the SLIC input
impedance must match theline impedance and
JUNC must be appropriately terminated.

Digital Applications

The 2-wire junctor output can be converted to a
4-wire circuit using the MH88524 (2-4 wire
converte r). This 4 wire circuit can be interfaced to a
filter/codec to use in digital voice switched systems.
Alternatively the MH88600/MH88612, digital ONS
SLIC can be us ed.

TYPICAL

RETURN
LOSS

(dB)

10
20

30
40
50

60

550

600 650

LOAD IMPEDANCE ON JUNCTOR (Ω)

700 750

800

850 900

Figure 4 - Return Loss VS Junctor Lo ad I mped ance

950

2-66

Preliminary Information MH88520-1

Absolute Maximum Ratings†

Parameter Symbol Min Max Units

1 Voltage Supplies

Referenced to GND

2 Clamp Diode Breakdown Vo ltage-V

to RGN D V

Ref

3 Operating Temperature T
4 Storage Temperatu re T
5 Power Dissipation P

† Exceeding these values ma y cause perm anen t dama ge. Functi onal operati on und er these cond ition s is not implied.

V
V
V

DD

EE

Bat

RLY

AMB

S

D

-0.3 +15 V

-15 0.3 V

-35 0.3 V
+32 V

0+70°C

-55 +125 °C

AC Electrical Characteristics†

Voltages are with respect to ground (VSS), TA = 25°C, unless otherwise stated.
Test conditions unless noted, V

Characteristics Sym Min Typ

1 Junctor to Differential Out put

(tip-ring) Gain

2 Differe ntia l; Input (tip-ring) to

Junctor Gain

3 On/Off Hook Detection Threshold

4 Transhybrid Loss 30 dB Notes 1,2

=5V, VEE=-5V, V

DD

Loop Current I

Bat

=-24V).

Thresh

‡

Max Units Test Conditions

-7.0 0 dB 1kHz, 0.5V source on
pin 16. Note 2

0.0 dB 1kHz, 0.5V
Applied on pins 1&3
Note 1, 2

8.0 10 12 mA Note 1

4

Watt

Source

5 Pas sband Frequency Response ±1.0

dB Notes 1,2

200Hz - 3400Hz

6 Power Supp ly V

Rejection Ratio V
(@ Junctor) V

BAT

DD

EE

7 Common Mode Rejection Ratio

(Tip and Ring to Junctor)
8 Longi tud inal Balance 46 50 dB
9 Junctor Out put Impedance Z
10 Return Loss at Tip, Ring 18 30 dB
11 Max. Signal Level 3 dB
12 Max. Ringing Voltage 105 V
13 Max. Ringing Frequency 25 60 Ηz
14 Idle Channel Noise

at T-R

at Junctor

15 Mute Attenuat ion 30 dB

† Exceeding these values ma y cause perm anen t dama ge. Functi onal operati on und er these cond ition s is not implied.
‡ Typical figures are at 25°C with nominal+
Note 1: 754Ω connected between JUNCTOR (pin 16) and 0V.
Note 2: German Impedance connected betwe en TIP (A) (pin 1) and RING (B) (pin 3).

5V supplies and are for design aid only: not guaranteed and not subject to production testing.

PSRR
PSRR
PSRR

30
40
40

dB
dB
dB

CMRR 40 dB

OJ

N

TR

N

J

604 Ω

-80

-80

-70

-75

dBmp
dBmp

RMS

Notes 1,2. Ripple

0.1V 1kHz

Notes 1,2
1kHz, 0.5V

Notes 1

1kHz Notes 1,2
Notes 1,2

Notes 1,2
Notes 1,2

2-67

MH88520-1 Preliminary Information

DC Electrical Characteristics

.

Characteristics S ym Min Typ

S

1

2 Operating Supply Current s

3

Operating Supply Voltages

U
P
P
L
Y

High Level Input Voltage

MUTE

RRC

4 Low Level Input Voltage

I

N
P
U

5 High Level Input Current

T
S

MUTE

RRC

MUTE

RRC

6 Low Level Input Current

MUTE

RRC

7

Sink Current

RRD

8 Relay to V

O

Diode Clamp Current I

U
T
P

9 High Level Output Voltage

U

SHK

T
S

10 Low Level Output Voltage

DD

SHK

LED

V
V
V

I

I

I

V

V

V

V

I
I

I
I

I

LED

I

RRD

RLY

V

V

DD
EE

Bat

DD

EE

Bat

IH
IH

IL
IL

OH

OL

‡

Max Units Test Conditions

4.5

-5.5

-30

IH
IH

IL
IL

2.0

4.5

65

5

-5

-24

5.5

-4.5

-20

8
6
1

0.8

0.5

-28

700

100

10

1.5

100 200

V
V
V

mA
mA
mA

V
V

V
V

µA
µA

µA
µA

mAmAV

On Hook

= RRC= 5V

RLY

RGND = 0V

< 1.5V

V

RRD

65 100 mA RRC=RGND=0V

= 5V

V

RLY

> 4.5V

V

RRD

4.5 5 5.5 V LED Unconnected

0.010.7VLED Unconnected

11 Low Level Output Current I
12 Power Consum ption P
13 Max. Operating loop R

‡ Typical figures are at 25°C with nominal+ 5V supplies and are for design aid only: not guaranteed and not subject to production testing.

OL

C

L

R

L

4 µA

600
900

mW 400Ω Loop

Ω

at 18mA, 24V

Ω

at 18mA, 30V

MH88520 Input Impedance

Variant Country Impedance

01 GERMANY 220Ω + 820Ω // 115nF

2-68

Preliminary Information MH88520-1

TIP

RING

RINGING

GENERATOR

90VRMS

Notes:

R1= 200Ω, 1/4W, 5%
K1= Relay E/M 5V, 1Form C
C1, C2 = 0.1uF, 50V, Ceramic

Optio nal

Protection

Circuit

Earth Ground

K1

R1

∼

-24V

1

TIP

3

RING

4

RF1

6

RF2

14

VBAT

VEE AGND

13 12 18

8

-5V
C1 C2

MH88520-1

VDD RGND

+5V

JUNC

MUTE

SHK

LED

RRC
RRD

VRLY

16

15

10

19

17

20

AUDIO
INPUT/OUTPUT

MUTE CONTROL
INPUT

SWITCH HOOK
OUTPUT

9

DS1

K1

OFF-HOOK LED

RING CONTROL
INPUT

R and R

R

60

50
40
30
20

10

(kΩ)

THRESH

11

THRESH

ADJ

SLIC

RG = 6000 x I

VDD - (501 x I)

I = Threshold current

in Amps

= +5V

V

DD

Figure 5 - Ty pic al Applicati on Circu it

GND

R and R

THRESH

SLIC

RV= (100 x VDD) - (6000 x I)

R

(kΩ)(kΩ)

RG(kΩ)

(a)

400

200

(kΩ)

11

THRESH

(501 x I) - VDD

VBAT

RVRG

ADJ

RV(kΩ)

(b)

23456

Figure 6 - Off-Hook Threshol d Adjust

78

10

15

20 25

2-69

MH88520-1 Preliminary Information

V

DD

-24VDC
+90VAC

+5V

RELAY COIL

TIP(a)

RING

RING FEED 1

RING FEED 2

VRLY

RRD

RRC

RGND

LINE FEED/
RING FEED

HYBRID

CLAMP DIODE

RELAY

DRIVE

CIRCUIT

Figure 7 - Relay Drive Circu it

2-70

Preliminary Information MH88520-1

CONTROL

LOGIC

ADDRESS

OUT

L

A

0-A2/D0-D3

MT8812

Crosspoint

Switch

0

A0
A1
A2

MD74SC137

1 OF 8

DECODER

A0
A1
A2

MD74SC137

1 OF 8

DECODER

J

0

J

1

J

2

J

3

-L

7

00
01

02
03
04

05
06

07

00
01

02
03

04
05
06

07

5 MORE

SLICS

5 MORE

SLICS

+7v +5V

212920174

15
19

MH885 20 -1

10

-8V -24V 0V

+5V

+7V

2

15

MH88520-1

19
10

+7V +5V +5V

15
19

10

86147

16

-8V

-24V

MH885 20 -1

16 8

+5V

TIP

RING

7146816

+5V

1720912

4
TIP

RING

0V

4

17209122

TIP

RING

614 7

-24VDC
90VAC

-24VDC

1
3

-24VDC
90VAC

-24VDC

1

3

-24VDC
90VAC

-24VDC

1

3

A0
A1
A2

SELECT

OUTPUT

CMOS

4512

8-INPUT

MUX

D

0

D

1

D

2

|
|
D

7

-8V

-24V

0V

Figure 8 - PABX Typi cal Appli catio n

2-71

MH88520-1 Preliminary Information

Side View

0.010 +
(0.25 +

Notes:

1) Not to scale

2) Dimensions in inches).

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

tolerance non accumulative.

0.00 2

0.05)

0.080 Ma x
(2.0 Max)

0.12 Max

(3.1 Max)

0.02

0.58+
1 2 3 4 19 20

0.5)

(14.7+

*

0.01

0.05 +
(1.3 +

0.5)
*

0.05 +

0.02

(1.3 +

0.05)

Figure 9 - Mechanical Data

0.020 +
(0.51 +

2.00+ 0.020

0.5)

(50.8 +

0.05

0.13)

*

0.100 +

(2.54 +

*

0.10

0.13)

0.8 +

(4.6 +

0.02

0.5)

2-72