MT91610AQ Zarlink Semiconductor, MT91610AQ Datasheet - Page 6

• Manufacturer Part Number: MT91610AQ
• Description: Description = Short Loop Subscriber Line Interface Circuit (SLIC) With 2-4 Wire Conversion, Programmable Line Impedance, Ringing Amplification And On-hook Transmission For Did ;; Package Type = Qsop ;; No. Of Pins = 36
• Manufacturer: Zarlink Semiconductor

MT91610
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 Z
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
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 Z
2) network balance impedance Z
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:
6
is used for both Ra and Rb.
o
= 220
NB
o
+ (820
//
Step 1: Gain Setting (R7, R8, R9, R10)
Gain 2 - 4 = 20 Log [ R8 / R7]
Gain 4 - 2 = 20 Log [0.891 * [R10 / R9)]
Step 2: Impedance Matching (R4, R5)
Z
where kZ
Z
600/(100+100) = k*(600)/R4
let k=500
kZ
500*600=R5
Step 3: Network Balance Impedance (R6)
Optimised Case Z
R6 = R7 * (R9 / R10) * 2.2446689 * ( Z
R6 = 300k
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:
where,
I = Desirable Loop Current
Zt = Ra + Rb + maximum DC loop resistance
VBAT = Battery voltage
VREF= DC voltage at VREF pin
{| I * Zt |} V < { | VBAT | - 6*VREF - 2} V
o
o
R4= 100k
o
R5= 300k
R6= 336.7k
choose R7 = 300k , R8 = 150k .
choose R9 = 200k , R10 = 200k .
/ ( Ra+Rb) = kZ
/ ( Ra+Rb) = kZ
-1 dB = 20 Log [0.891 * [R10/ R9)]
= R5
-6 dB = 20 Log [R8 / R7]
Z
o
Gain 2 - 4 = -6dB, Gain 4 - 2 = -1 dB
= 600 , Z
o
= R5
* (1) * 1.1223344
o
o
o
= Z
NB
/ R4,
/ R4
Preliminary Information
= 600 , Ra=Rb= 100
NB
NB
/ Z
NB
+ Z
o
)