MT91610 데이터 시트보기 (PDF) - Zarlink Semiconductor Inc

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MT91610

Programmable Ringing SLIC

Zarlink Semiconductor Inc 

MT91610

Preliminary Information

Power Down And Wake Up

The MT91610 should normally be powered down to

conserve energy by setting the PD pin to +5V. The

SHK pin will be asserted if the equipment side (2

wire) goes off hook. The local controller should then

restore power to the SLIC for normal operations by

setting the PD pin to 0V.

Please note that there will be a short break (about

80ms) in the assertion time of SHK due to the time

required for the loop to power up and loop current to

flow. The local controller should be able to mask out

this time.

Meter Pulse Injection

The MT91610 provides a gain path input (ESI) for

meter pulse injection and an independent control

logic input (ESE) for turning the meter pulse signal

on and off.

Gain (meter pulse) = 20 Log [0.891 * (R10 / R11)]

with configuration targeting Zo = 220 Ω + (820 Ω //

115nF)

Component Selection

Feed Resistors

The selection of feed resistors, Ra and Rb, can

significantly affect the performance of the MT91610.

The value of 100 Ω is used for both Ra and Rb.

The resistors should have a tolerance of 1% (0.1%

matched) and a power rating of 0.5 Watt.

Calculating Component Values

There are five parameters a designer should know

before starting the component calculations. These

five parameters are:

1) characteristic impedance of the line Zo

2) network balance impedance ZNB

3) value of the feed resistors (Ra and Rb)

4) 2W to 4W transmit gain

5) 4W to 2W receive gain

The following example will outline a step by step

procedure for calculating component values. Given:

Zo = 600Ω, ZNB= 600Ω, Ra=Rb= 100Ω

Gain 2 - 4 = -6dB, Gain 4 - 2 = -1 dB

Step 1: Gain Setting (R7, R8, R9, R10)

Gain 2 - 4 = 20 Log [ R8 / R7]

-6 dB = 20 Log [R8 / R7]

∴ choose R7 = 300kΩ, R8 = 150kΩ.

Gain 4 - 2 = 20 Log [0.891 * [R10 / R9)]

-1 dB = 20 Log [0.891 * [R10/ R9)]

∴ choose R9 = 200kΩ, R10 = 200kΩ.

Step 2: Impedance Matching (R4, R5)

Zo / ( Ra+Rb) = kZo / R4,

where kZo = R5

Zo / ( Ra+Rb) = kZo / R4

600/(100+100) = k*(600)/R4

let k=500

∴ R4= 100kΩ

kZo = R5

500*600=R5

∴ R5= 300kΩ

Step 3: Network Balance Impedance (R6)

Optimised Case Zo = ZNB

R6 = R7 * (R9 / R10) * 2.2446689 * ( ZNB / ZNB + Zo)

R6 = 300kΩ * (1) * 1.1223344

∴ R6= 336.7kΩ

Step 4: The Loop Current (R2)

In order to remain in constant current mode during

normal operation, it is necessary that the following

equation holds:

{| I * Zt |} V < { | VBAT | - 6*VREF - 2} V

where,

I = Desirable Loop Current

Zt = Ra + Rb + maximum DC loop resistance

VBAT = Battery voltage

VREF= DC voltage at VREF pin

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