2-173

Features

Dual SLIC

Ringing generation

On-hook transmission

Transformerless 2-4 wire conversion

Constant current feed

Battery Feed to the line

Tip Ring reversal capability

Over current protection

Off-Hook detection

Logic interface for SHK, RC, LR, ESE, LCS

Metering injection

Wide V

Bat

operating range

Minimum installation space

ESE ramped output

Applications

Pair Gain

CT2

Cordless local loops

Description

The Mitel MH88622 is a Dual Subscriber Interface
Circuit which provides a complete interface between
the telephone lines a dual codec, requiring a dual rail
supply, battery and dc supply for ringing generation.
The functions provided by the MH88622 includes 2-4
Wire conversion, constant current line feed,
signalling and control. The SLIC manufactured using
thick film hybrid technology which offers high voltage
capability, reliability and high density resulting in a
significant area saving on the printed circuit board. A
complete C.O. type solution can be implemented
with minimal external components. Different variants
are provided to meet different country line
impedance, they are:

-1 220

+ (820

// 115nF)

-2 600

-3 370

+ (620

// 310nF)

-5

200

+ (680

// 100nF)

Figure 1 - Functional Block Diagram

Loop

Supervision

Line Drivers/

Feed

Over Current

Protection &

Constant

Current Feed

Over Current

Protection &

Constant

Current Feed

Loop

Supervision

Line Drivers/

Feed

2-4 Wire

Conversion

2-4 Wire

Conversion

Ring Generator

SHK1

LR1

TIP1

RING1

VX1

VR1

ESI1

VDD VEE AGND

VBat

DCRI RC1 RF1 RF2 RGV RG1 RC2

SHK2

LR2
TIP2
RING2

VX2
VR2
ESI2
ESE2

LCS1

LCS2

ESE1

ISSUE 3

April 1995

Ordering Information

MH88622 -1, -2, -3,-5 40 Pin SIL Package

C to 70

MH88622

DUAL OPS SLIC

Preliminary Information

2-174

MH88622

Preliminary Information

Figure 2 - Pin Connections

Pin Description

Pin #

Name

Description

TIP1

Tip Lead. Connects to the "TIP" lead of subscriber line 1.

RING1

Ring Lead. Connects to the "RING" lead of subscriber line 1.

BAT

Battery Voltage. Typically -48V dc is applied to this pin. This should be connected to pin 38
of the hybrid on the PCB.

DCRI

DC Ringing Voltage Input. A continuous 120V dc is applied to this input to achieve
90Vrms ringing. This should be connected to pin 37 of the hybrid.

GND

Ground. This pin should be tied to pins 13, 28 & 36 on the PCB.

ESI1

External Signal Input (Input). A continuous signal should be applied to this pin which will
be switched to "Tip" and "Ring" of subscriber 1.

ESE1

External Signal Enable (Input). The external signal to the subscriber 1 is controlled by a
logic level applied to this pin.

VR1

Receive (Input). 4-Wire GND referenced audio input for subscriber 1.

SHK1

Off Hook Indication (Output). A logic low output indicates when subscriber 1 equipment
has gone off hook.

LCS1

Loop Current Set 1. Logic 1 gives I

Loop

= 40mA, Logic 0 gives I

Loop

= 25mA

VX1

Transmit (Output). 4-Wire, GND referenced audio output for subscriber 1.

VEE

Negative Supply Voltage. -5Vdc. Connects to pin 29 of the hybrid on the PCB.

GND

Ground. Return path for VDD, VEE, VBat & DCRI. This pin should be connected to pins 5,
28 & 36 of the hybrid on the PCB.

VDD

Positive Supply Voltage. +5Vdc. Connect to pin 27 of the hybrid on the PCB.

LR1

Line Reversal. A logic 1 applied to LR1 will reverse the "Tip" and "Ring" to subscriber 1.
This pin has an internal pull down.

RC1

Ringing Control (Input). A logic level applied to this pin enables ringing to be applied
across Tip and Ring of subscriber 1.

RGV

RG1

NC
NC

RC2

LR2

VDD

GND

VEE

VX2

LCS2

SHK2

VR2

ESE2

ESI2

GND

DCRI

VBat

RING2

TIP2

TIP1

RING1

VBAT

DCRI

GND
ESI1

ESE1

VR1

SHK1

LCS1

VX1

VEE

GND

VDD

LR1

RC1

NC
NC

RF1
RF2

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

21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

2-175

Preliminary Information

MH88622

No Connection. This pin should not be connected.

No Connection. This pin should not be connected.

RF1

Ringing Frequency Node 1 (Input). A capacitor is connected between RF1 & RF2 and
determines the frequency of the ringing generator.

RF2

Ringing Frequency Node 2 (Input). Two capacitors are connected between RF1& RF2
and from RF2 to AGND. This determines the frequency of the ringing generator.

RGV

Ringing Gain Voltage. Connects to RG1 through a resistor to reduce the output ringing
voltage. When left open circuit output ringing voltage is 90Vrms.

RG1

Ringing Gain Node 1. Connects to RGV through a resistor to reduce the output ringing
voltage. When left open circuit output ringing voltage is 90Vrms.

No Connection. This pin should not be connected.

RC2

Ringing Control (Input). A logic level applied to this pin enables ringing to be applied
across Tip and Ring of subscriber 2.

LR2

Line Reversal. A logic 1 applied to LR2 will reverse the "Tip" and "Ring" to subscriber 2.
This pin has an internal pull down.

VDD

Positive Supply Voltage. +5Vdc. This pin should be connected to pin 14 of the hybrid on
the PCB.

GND

Ground. Return path for VDD, VEE, VBat & DCRI. This pin should be connected to pins 5,
13 & 36 of the hybrid on the pcb.

VEE

Negative Supply Voltage

-5Vdc. This pin should be connected to pin 12 of the hybrid on

the PCB.

VX2

Transmit (Output). 4-Wire GND referenced audio input for subscriber 2.

LCS2

Loop Current Set 2. Logic 1 gives ILoop = 40mA, Logic 0 gives ILoop = 25mA.

SHK2

Off Hook Indication (Output). A logic high output indicates when subscriber 2 equipment
has gone off hook.

VR2

Receive (Input). 4-Wire GND referenced audio input for subscriber 2.

ESE2

External Signal Enable (Input). The external signal to subscriber 2 is controlled by a logic
level applied to this pin.

ESI2

External Signal Input. A continuous signal should be applied to this pin which will be
switched to "Tip" and "Ring" of subscriber 2.

GND

Ground. This pin should be tied to pins 5, 13 & 28 on the PCB.

DCRI

DC Ringing Voltage Input. A continuous 120Vdc is applied to this input to achieve 90
Vrms ringing. This should be connected to pin 4 of the hybrid on the PCB.

VBAT

Battery Voltage. Typically -48V dc is applied to this pin. This should be connected to pin 3
of the hybrid on the PCB.

RING2

Ring Lead. Connects to the "Ring" lead of subscriber line 2.

TIP2

Tip Lead. Connects to the "Tip" lead of subscriber line 2.

Pin Description (Continued)

Pin #

Name

Description

2-176

MH88622

Preliminary Information

Absolute Maximum Ratings *-

All voltages are with respect to GNDA unless otherwise stated.

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

DC Electrical Characteristics

* Typical figures are at 25°C with nominal +5V supplies and are for design aid only.

Max & Min figures guaranteed over 0

C to 70

C only

Parameter

Symbol

Min

Max

Units

Supply Voltages - Referenced to V

(GND)

DCRI

Bat

+0.3

-0.3
-0.3

-60

-15

+15

+180

0.3

V
V
V
V

Operating Temperature

TAMB

-40

+85

°C

Storage Temperature

-55

+125

°C

Characteristics

Sym

Min

Typ*

Max

Units

Test Comments

S
U
P
P

Operating Loop Current

DCRI

Bat

-4.75

4.75

110

-60

-5

120

-48

-5.25

5.25

160

-20

V
V
V
V

Operating Supply Current
(per Channel)

DCRI

Bat

30
30
15

mA
mA
mA

On-hook
On-Hook
Ringing
(REN=1)
Idle

N
P
U

T
S

High Level Input Voltage LR,
RC, ESE, LCS

4.5

Low Level Input Voltage LR,
RC, ESE, LCS

0.5

High Level Input Current LR,
RC, ESE, LCS

700

Low Level Input Current LR,
RC, ESE, LCS

O
U

T
P

T
S

High Level Output Current
SHK

0.4

Low Level Output Current
SHK

High Level Output Voltage
SHK

4.75

Low Level Output Voltage
SHK

0.4

Constant Current Line Feed

Loop

LCS = 0

Maximum Operating Loop

500

1500

@ 25mA -24V
@ 25mA -48V
inclusive of telephone
set

Power Consumption

300

Excluding P

BAT

& P

DCRI

2-177

Preliminary Information

MH88622

AC Electrical Characteristics*

Characteristics

Sym

Min

Typ

Max

Units

Test Comments

Gain VR to 2-Wire

Gain relative to Gain @ 1kHz

-0.2

+0.15

+0.2

Input 1.0Vrms 1kHz @ VR,
Zload = Z

300-3.4kHz

Gain 2-wire to VX

Gain relative to Gain @ 1kHz

-6.2

-6

+0.15

-5.8

Input 3dBm 1kHz @ 2W
Zsource = Z

300-3.4kHz

Off-Hook Detect Threshold

7.5

Transhybrid Loss

THL

300-3.4kHz

Ringing Signal Voltage

Vrms Min 65Vdc differential between

DCRI & V

BAT

Ringing Frequency

See Table 1

Ringing Capability

REN

1750

impedance @ 20Hz min.

Power Supply Rejection Ratio

Bat

DCRI

PSRR

30
30
30

Ripple
0.1 VPP 1kHz

2-wire Return Loss

Input 0.5 Vrms 1kHz across Tip
& Ring Zload = Z

10 Longitudinal to Metallic Balance

-1 Variant

-2 Variant

-3 Variant
-5 Variant

Metallic to Longitudinal Balance

-2 Variant only

40
55
53
58
53
46
40
46

60
40

dB
dB
dB
dB
dB
dB
dB
dB

dB
dB

Input 0.5Vrms
50-300Hz
300-1000Hz
1k-4kHz
200Hz to 1kHz
3kHz
300Hz to 3k4Hz
300Hz to 600Hz
600Hz to 3k4Hz

200Hz to 1kHz
1kHz to 4kHz

11 Input AC Impedance (2- wire)

-1 variant (220

+ 820

// 115nF)

-2 variant (600

)

-3 variant (370

+ 620

// 310nF)

-5 variant (200

+ 680

// 100nF)

600
900
700
823

1kHz @ 2-wire

12 Input Impedance @ VR

230

13 Output Impedance @ VR

14 Total Harmonic Distortion

at VX

at Tip & Ring

THD

0.2
0.2

%
%

Input 4dBm @2-Wire
Input 1V at VR

15 Common Mode Rejection

Ratio 2-Wire to VX

CMRR

Input 0,5V, 1kHz

16 Idle Channel Noise

at VX

at 2-wire

15
15

dBrn

17 On-Hook Transmission Signal

Input Level Gain

2.0

Vrms

Bat

= -48V

T-R load = 10k

min.

18 External Signal Output Level

1.75

2.2

Vrms V

Bat

= -48V

T-R load = 200

2-178

MH88622

Preliminary Information

* AC Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated.
Typical figures are at 25°C with nominal + 5V supplies and are for design aid only.
Max and Min figures guaranteed over 0

C to 70

C only.

Notes: Impedance set to variant impedance
Test conditions uses a Z

value as specified by variant number.

Test conditions use a transmit and receive gain set to 0dB default and a Z

value of 600

unless otherwise stated.

Figure 3 - Loop Start SLIC Configuration Application Circuit

19 SHK Rise Time

Fall Time

1
1

ms
ms

Dial Pulse
Detection

20 Analogue Signal Overload Level

@ Tip & Ring

dBm

@ 1kHz

21 Ring Trip Delay

100

22 Outband Noise

-70

Refer to BS6305 section 4.1.4 &
fig 3 for details of limits

23 Crosstalk

Channel 1 to 2
Channel 2 to 1

-80
-80

dB
dB

@ 1kHz

AC Electrical Characteristics* (Continued)

Characteristics

Sym

Min

Typ

Max

Units

Test Comments

-5V

+5V

GND

VR1

VX1

RC1

LR1

ESE1

ESI1

SHK1

SHK2

VR2

VX2

RC2

LR2

DCRI

ESE2

ESI2

TIP2

RING2

Bat

CODEC

LINE

CONTROLLER

LOGIC

SUBSCRIBER 1

RGV

RG1

CODEC

SUBSCRIBER 2

12/16kHz
SOURCE

120VDC

SUPPLY

TIP1

RING1

SUBSCRIBER 1

SUBSCRIBER 2

CF1

CF2

RF1

RF2

DCRI

Preliminary Information

MH88622

2-179

Functional Description

The SLIC uses a Transformerless 2-4 Wire converter
for each subscriber which can be connected to a
CODEC to interface the 2-Wire subscriber loop to a
time division multiplexed (TDM), pulse code
modulated (PCM), digital link.

Powering of the subscriber line is provided through
precision battery feed resistors on the hybrid. The
thick film hybrid circuit contains control, signalling
and status circuits which combine to provide a
complete solution simplifying the manufacture of line
cards.

Approvals

FCC part 68, CCITT, DOS CS-03, UL 1459, CAN/
CSA-22.2 N0. 225-M90 and ANSI/EIA/TIA-464-A are
system level safety standards and performance
requirements. As a component of a system, the
MH88622 is designed to comply with the applicable
requirements of these specifications.

Battery Feed

The SLIC is designed for a nominal battery voltage
of -48 Vdc and can provide the constant feed current
for 1500

loop under this condition.

The interface circuit is designed to be operated up to
a maximum of -60V dc battery feed voltage without
damage, providing a minimum loop length capability
of 2000

There is also a function on the SLIC that provides for
Tip-Ring reversal.

Current Limit

Primary over current protection is inherent in the
current limiting feature of the battery feed circuit.

Current limiting is provided for both Tip and Ring
unbalanced conditions.

The maximum loop current limit is set internally on
the interface and current limiting does not affect the
longitudinal or the signal balance of the device. To
set I

Loop

to 40mA tie the LCS pin high (Logic 1), to

set I

Loop

to 25mA the LCS pin may be left open circuit

or tied low (Logic 0).

Two Wire Port Termination Impedance

The Tip/Ring impedance (Z

) is fixed for each

variant.

Transmit and Receive Gain

The transmit and receive gain of the MH88622 is
internally set.

Internal Ringing Generator

The MH88622 offers an on board ringing generator
requiring only two external passive components and
a DC voltage source to produce a sine wave of
between 17Hz to 68Hz.

An internal signal is amplified by a user programmed
amount and is applied to Tip and Ring. The
programmable gain must be set using RGV and RG1
to ensure that distortion of the ringing signal is
minimised.

With V

BAT

= -48Vdc and V

DCRI

+120Vdc and the

ringing voltage = 90Vrms RGV and RG1 should be left
open circuit. By adding an external resistor between
RGV and RG1 it is possible to reduce the ringing
voltage applied by the driver section to Tip and Ring.

The DC voltage source should be continuously applied
to the MH88622. The ringing voltage will only be
applied when the RC pin of the relevant subscriber is
activated.

Table 1 - Ring Generator Capacitor Selection

12-16kHz Meter Pulse

The MH88622 provides control of an external signal
path to the driver. A 12/16 KHz continuous signal
should be applied to the ESI pin. Control of the ESE
input allows the metering signal to be transmitted to
the line with a ramped up and down amplitude to
reduce noise on the line. Typical ramp time is 10mS.

Typ. Frequency

(Hz)

CF1, CF2

(nF)

100

2-180

MH88622

Preliminary Information

Figure 4 - Typical Protection Circuit

PROTECTION

PTC
RESISTOR

5 Ohms

TISP2290

P2702AB

PTC

RESISTOR

5 Ohms

Off-Hook and Dial Pulse Detection

The SHK pin goes low when e DC loop current
exceeds a specified level. The threshold level is
internally set by the bias voltage of the switch hook
detect circuit.

Dial pulse can be detected by monitoring the
interruption rate at the SHK pin. These dial pulses may
need to be debounced by the systems software.

Ring Trip Detection

The interface permits detection of an Off-Hook
condition during ringing. If the subscriber set goes
Off-Hook when the ringing signal has been applied,
the DC loop current flow will be detected within
approx. 100msecs and the SHK output will go low.
The ringing is automatically disabled by the internal
hardware.

Longitudinal Balance

Precision laser trimming of resistors in the hybrids
ensures good overall longitudinal balance.

The interface circuitry can operate in the presence of
induced longitudinal currents of up to 40mA rms at
60Hz.

High Voltage Capability

Inherent in the thick film process is the ability of the
thick film process dielectric strengths of greater than
1000 VAC or 1500 VDC. The thick film process
allows easy integration of surface mount
components such as the high voltage bi-polar power
transistor line drivers. This allows for simpler, less
elaborate and less expensive protection circuitry
required to handle high voltage transients and fault
conditions caused by lightening, induced voltages
and power line crossing.

On Hook Transmission

The MH88622 provides for on-hook transmission
which supports features such as Automatic Number
identifications (ANI).

Loop Length

The MH88622 can accommodate loop length of up to
2000

minimum (including the subscriber

equipment).

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