MT91600 Mitel Networks Corporation, MT91600 Datasheet - Page 5

• Manufacturer Part Number: MT91600
• Description: Programmable Slic
• Manufacturer: Mitel Networks Corporation

Preliminary Information
When using DTMF signalling only i.e. pulse dialling
is not used, the capacitor, C7, can be permanently
connected to ground and does not require to be
switched out during dialling.
Power up Sequence
The circuit should be powered up in the following
order: AGND, VEE, VDD, V
Application
The following Application section is intended to
demonstrate to the user the methods used in
calculating and selecting the external programming
components in implementing the MT91600 as an
analog line interface in a communication system.
The programming component values calculated
below results in the optimum performance of the
device.
Refer to Figure 5 for MT91600 components
designation.
Component Selection
Feed Resistors (R1, R2)
The selection of feed resistors, R1 and R2, can
significantly affect the performance of the MT91600.
It is recommended that their values fall in the range
of:
where, R1 = R2
The resistors should have a tolerance of 1% (0.15%
matched) and a power rating of 1 Watt.
Loop Current Setting (R3, R4, C9)
By using a resistive divider network, (Figure 3), it is
possible to maintain the required voltage at Vref to
set I
the following relationship:
I
where,
LOOP
LOOP
= - [ F * V
. The loop current programming is based on
F = R4 / (R4 + R3)
G = R3 / (R4 +R3)
K
H = 1.07
I
LOOP
o
= 200000 / (200000 + (R4//R3) )
200
is in Ampere
LC
+ G * V
(R1 +R2)
<= R1 <= 250
BAT
BAT.
] * K
o
* H
From Figure 3 with R1 = R2 = 220
For I
C9 is inserted to ensure pin 6, Vref, remains at a.c.
ground. 100nF is recommended.
I
low impedance voltage source. (See Figure 4). It is
recommended that a small resistor be placed in
series with the Vref pin. In this case:
I
Calculating Component Values For AC
Transmission
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 (R1 and R2)
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:
LOOP
LOOP
V
LC
LOOP
can also be set by directly driving Vref with a
= 1.07 * Vs
Vs
(R1 +R2)
R3
43k
= 25mA, V
Figure 3 - Resistor Divider
Figure 4 - Direct Voltage
2k
100nF
C9
100nF
C9
LC
= 0V, Vbat=-48V
130k
R4
where, Vs < 0
V
BAT
NB
6
6
MT91600
V
V
MT91600
MT91600
REF
REF
o
5