MH88622-2 Просмотр технического описания (PDF) - Mitel Networks

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MH88622-2

DUAL OPS SLIC

Mitel Networks 

Preliminary Information

MH88622

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 1500Ω 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 2000Ω.

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

set ILoop to 25mA the LCS pin may be left open circuit

or tied low (Logic 0).

Two Wire Port Termination Impedance

The Tip/Ring impedance (Zin) 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 VBAT = -48Vdc and VDCRI = +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.

Typ. Frequency

(Hz)

CF1, CF2

(nF)

17

100

25

68

35

47

50

33

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.

2-179

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