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MH88617AV-PI

Programmable SLIC with Ringing Amplification

Mitel Networks 

MH88617

Advance Information

of applications this will not be a problem, however

the device could be damaged if used to drive a very

short line with the maximum battery voltage and

maximum programmable loop current.

For very long loops the constant current drive reverts

to a constant voltage source. A graph of loop current

versus line resistance is shown in Figure 4.

Under fault conditions, Tip or Ring are protected

from short circuits to ground when the current

exceeds the protection trip threshold. Under these

circumstances, the SLIC will go into a power down

mode and periodically check the line status until the

fault has been removed. Thereby minimizing power

dissipation. The SLIC will revert to an operational

state once the fault is removed.

Ringing Amplification

The MH88617 incorporates an internal ringing

amplifier circuit. A balanced ringing signal is applied

across Tip and Ring, when a DC voltage is

connected to the DCRI pin, a low level sinusoidal

signal is applied to RV and RC is set to logic 1. The

ringing voltage is approximately 50 times the signal

at RV. The gain depends on the ringer load and

impedance at ZA. If an absolute gain is required, a

transistor can be fitted across ZA to give 42.

The SLIC also has the ability to provide ringing on

short loops without the need for a high voltage DCRI

supply. This is achieved by connecting the DCRI pin

to a low voltage supply such as +5V or +12V

providing the subscriber equipment ringing detector

has a low enough sensitivity threshold. In this

application the input at RV needs to be a square

wave (refer MSAN-156).

The SLIC has an automatic ring-trip circuit that

ensures the ringing is removed when the subscriber

goes off-hook. However the user must still insure RC

is taken to logic 0 when SHK signals the subscriber

has gone off-hook.

Programmable Input Impedance

By connecting external passive components

between ZA and ground (AGND) the device’s input

impedance can be set to match the line impedance.

As shown in Figure 3 and Table 1. A more

comprehensive list is given in MSAN-156.

Programmable Network Balance

The network balance of the device can be

programmed by connecting external passive

components between GVX and VR, as shown in

Figure 3 and Table 1.

+5V -5V -48V 0-100V

C1

C2

+5V

1.0Vrms

Sinewave

(16-68Hz)

F1

TIP

E.G Teccor

P2353AB

F2

RING

SHK

Relay Drive

Output

Loop Current

Adjust Input

Protection

Circuit

VCC VEE VBAT DCRI RV

TIP

MH88617

RING

LR

RDI

ESE

RC

VX

SHK

RDO

LCA

AGND

ZA

GVX

VR

ESI

10k

MT896x

SD3

SD2

SD1

SD0

VX

R1

T

R2

Z2

VR

Notes:

Z1

1) For Resistor and Impedance values

see Table 1

2) C1 and C2 are 100nF decoupling capacitors

3) F1 and F2 Slow Blow Fuses

Figure 3 - Typical Application Circuit

1.0Vrms

Sinewave

(12/16kHz)

2-160

CA

F1i

CLK

DSTi

DSTo

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