MT9173 Datasheet, PDF (16/28 Pages) Mitel Networks Corporation – Digital Subscriber Interface Circuit with RxSB

MT9173/74
Data Sheet
Applications
Typical connection diagrams are shown in Figures 13 and 14 for the DN mode as a MASTER and SLAVE,
respectively. L_OUT is connected to the coupling transformer through a resistor R2 and capacitors C2 and C2’ to
match the line characteristic impedance. Suggested values of R2, C2 and C2’ for 80 and 160 kbit/s operation are
provided in Figures 13 and 14. Overvoltage protection is provided by R1, D1 and D2. C1 is present to properly bias
the received line signal for the L_IN input. A 2:1 coupling transformer is used to couple to the line with a secondary
center tap for optional phantom power feed. Varistors have been shown for surge protection against such things as
lightning strikes.
If the scramblers power up with all zeros in them, they are not capable of randomizing all-zeros data sequence. This
increases the correlation between the transmit and receive data which may cause loss of convergence in the echo
canceller and high bit error rates.
In DN mode the insertion of the SYNC pattern will provide enough pseudo-random activity to maintain
convergence. In MOD mode the SYNC pattern is not inserted. For this reason, at least on ”1” must be fed into the
DNIC on power up to ensure that the scramblers will randomize any subsequent all-zeros sequence.
DV Port ST-BUS _{
CD Port ST-BUS {
Master Clocks {
Mode Select
Lines
+5 V
0.33 µF
0.33 µF
To Time
Measurement
Circuitry
MT9173/74
DSTi
DSTo
CDSTi
CDSTo
F0
C4
MS0
MS1
MS2
V_Ref
V_Bias
L_OUT
L_IN
OSC1
OSC2
F0o
RxSB
C2’ = 1.5 nF
C2 = 22 nF
+5 V
D1 = D2 = MUR405
For 80 kbit/s: C2’ = 3.3 nF
R2 = 390 Ω
R1 = 47 Ω
2:1
D2
D.C. coupled,
Frequency locked
10.24 MHz clock.
NC ^{Refer to AC Electrical}
Characteristics
Clock Timing
DN Mode.
C1 = 0.33 µF
Line Feed
Voltage
1.0 µF
68 Volts
(Typ)
2.5 Joules
0.02 Watt
To Next DNIC
Note: Low leakage diodes (1 & 2) are required so
that the DC voltage at L_IN ª V_Bias
Figure 13 - Typical Connection Diagram - MAS/DN Mode, 160 kbit/s
16
Zarlink Semiconductor Inc.