MT91600 Datasheet, PDF (4/18 Pages) Mitel Networks Corporation – Programmable SLIC

MT91600
Data Sheet
Impedance Programming
The MT91600 allows the designer to set the device’s impedance across TIP and RING, (Z_TR), and network balance
impedance, (Z_NB), separately with external low cost components.
For a resistive load, the impedance (Z_TR) is set by R11 and R18. For a complex load, the impedance (Z_TR) is set by
R11, R18, R19 & C8 (see Figure 5.)
The network balance, (Z_NB), is set by R16, R17 & C3 (see Figure 5.)
The network balance impedance should be calculated once the 2W - 4W gain has been set.
Line Impedance
For optimum performance, the characteristic impedance of the line, (Z_o), and the device’s impedance across TIP
and RING, (Z_TR), should match. Therefore:
Z_o = Z_TR
The relationship between Z_o and the components that set Z_TR is given by the formula:
Z_o / ( R1+R2) = kZ_o / R11
where kZ_o = Z_LZ
Z_LZ = R18, for a resistive load.
Z_LZ = [R18 + (R19 // C8)], for a complex load.
The value of k can be set by the designer to be any value between 20 and 250. Three rules to ensure the correct
operation of the circuit:
(A) R18 + R19 > 50kΩ
(B) R1 = R2.
(C) R11 > =50kΩ
It is advisable to place these components as close as possible to the SLIC.
Network Balance Impedance
The network balance impedance, (Z_NB), will set the transhybrid loss performance for the circuit. The balance of the
circuit is independent of the 4 - 2 Wire gain but is a function of the 2 - 4 Wire gain.
The method of setting the values for R16 and R17 is given by the formula:
R17 = [1.782 * Z_o / ( Z_o+Z_NB) * ( R13 / R12 )]
R17 + R16
[1 + R13 / R12]
where Z_NB is the network balance impedance of the SLIC and Z_o is the line impedance.
(R16 + R17) >= 50kΩ
It is advisable to place these components as close as possible to the SLIC.
4
Zarlink Semiconductor Inc.