MH88617AT-PI データシートの表示（PDF） - Mitel Networks

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MH88617AT-PI

Programmable SLIC with Ringing Amplification

Mitel Networks 

Advance Information

ILOOP

24mA

VBAT @ -48V

LCA O/C

MH88617

14mA

Constant

Current

Constant

Voltage

0Ω

≈1800Ω

≈2800Ω

Figure 4 - Loop Current vs. Line Resistance

RLOOP

Table 1 gives table of values for some common

applications. A more comprehensive list is given in

MSAN-156.

Programmable Transmit and Receive

Gain

The transmit gain from Tip and Ring to VX can be

programmed by connecting a resistor between GVX

and VX. Similarly the Receive Gain from VR to Tip

and Ring can be programmed by connecting an

impedance in series with VR as shown in Figure 3

and Table 1. Refer to MSAN-156 for additional

impedances.

Off-Hook and Dial Pulse Detection

for optimum performance forward operation is

recommended.

Meter-Pulse Injection

If the External Signal Enable (ESE) is taken to logic

1 and a 12kHz or 16kHz Meter Pulse signal is

applied to the ESI pin then this signal will be

amplified and output across Tip and Ring. This is

used for calculating the cost of a telephone call.

The gain of the meter pulse signal varies with

programmed input impedance e.g. with the input

impedance programmed for 600Ω and a 200Ω AC

load applied across Tip and Ring the ESI signal will

be amplified by a factor of 2.

The switch hook detect output (SHK) goes to a logic

1, when loop current is above the detect threshold

(see DC Electrical Characteristics). This occurs

when the subscriber’s equipment seizes the line to

initiate a call or answer a call. When loop disconnect

dialling is being used, SHK pulses to logic 0 to

indicate the digits being dialled. This output should

be debounced by the system software.

During On-hook transmission SHK remains at logic

0.

Reversal

During normal operation i.e. LR connected to logic 1,

the DC voltage on Tip is positive with respect to

Ring. This can be reversed by applying a logic 0 to

the Line Reversal pin (LR). This feature is used for

signalling. The SLIC is functional during reversal but

Some applications require the 12/16 kHz meter

pulse signal to be ramped before being input at ESI.

Power Down

If AGND is applied to LCA pin the MH88617 will

enter a power down mode where the internal circuitry

is turned off and the power consumption is reduced.

This can be used to conserve power when the line is

inactive.

If the system wants to initiate a call the AGND must

be removed from the LCA before the ringing signal is

transmitted.

If the subscriber initiates a call by seizing the line, SHK

will go to logic 1. The system should monitor this and

respond by removing the AGND from LCA causing the

device to wake up.

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