MH88520-1 데이터 시트보기 (PDF) - Mitel Networks

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MH88520-1

German Subscriber Line Interface Circuit (SLIC)

Mitel Networks 

MH88520-1

Preliminary Information

Ringing

Line Impedance

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 (90VRMS typically) and DC line

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

Telephone Impedance + 600

Amps

The positive supply for the line feed circuit is VDD

though the loop current is determined from Ring

Feed and GND.

The MH88520-1’s Tip-Ring (Zin) impedance is fixed

at the German complex impedance. For correct SLIC

impedance, JUNC must be appropriately terminated.

See AC Electrical Characteristics.

Transmit and Receive Gain

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

converter). 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 used.

TYPICAL

RETURN

LOSS

(dB)

10

20

30

40

50

60

550 600 650 700 750 800 850 900 950

LOAD IMPEDANCE ON JUNCTOR (Ω)

Figure 4 - Return Loss VS Junctor Load Impedance

2-66

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