MSAN-141 Zarlink Semiconductor, Inc., MSAN-141 Datasheet - Page 21

• Manufacturer Part Number: MSAN-141
• Description: Implementation Details of the MT8930B-31B S-T Interface
• Manufacturer: Zarlink Semiconductor, Inc.

Application Note
7.0
In compliance with ANSI T1.605 Specification, the
following power fault conditions should not damage
either the NT or the TE:
1.
2.
3.
For part 1 and 2, voltages of each polarity should be
applied between each of the 4-wire S interfaces, and
each other of these wires and the ground reference
of equipment power source. For part 3, fifty surges of
each polarity should be applied between all 4 wires
and the ground reference of the equipment power
source. Each surge is to be simultaneously coupled
to individual S interface wires, each through an
impedance of 15 nF, balanced with respect to
individual wires of the circuit pair.
The selection of the appropriate protection circuitry
to meet these conditions is restricted by the value of
the contributed total capacitance. This value must
not exceed 80 pF when measured on the line side.
DC voltage:
AC voltage:
Voltage surge: a) Amplitude: 1000 V peak
PROTECTION CIRCUITRY
Termination:
1. Z
2. Z
T
T
= 400
=
a
b
c) Duration: continuous for 5
c) Duration: 2 sec on, 4 sec off,
a) Amplitude: 56.5 V
b) Current limit: 0.5A
a) Amplitude: 200 V peak
b) Source resistance: 1500
b) Rise time: 1 s
c) Fall time: 50 s
d) Source capacitance: 15 nF
50
1M
minutes
continuous for 5 minutes
Figure 25 - Longitudinal Conversion Loss Test Circuit
10 F
68pF
E
L
50
50
LCL = 20 LOG
100
T1
Otherwise, this added capacitance will prevent the
device from complying with I.430 pulse and
impedance templates.
One protection circuit which has been proved to
meet all the stated power fault conditions on the line
side, and provide added protection to the output and
input drivers on the device side, is given in Figure 26.
The total capacitance contributed by this circuit can
be as low as 20 pF (when measured on the transmit
pair of the line side) depending upon the type of
diodes used. These diodes should have similar or
better electrical characteristics than the ones stated
below (typical diodes are the 1N916, 1N4149,
1N4448,
1N3600):
V
T
Figure 26 - Protection Circuitry for the SNIC
Note: The two diodes at the V
meet I.430 power fault conditions, but they are added for
extra protection.
(
E
V
L
T
SNIC
)
V
1N4449,
LRx
LTx
Bias
DUT
1 : 2
V
Notes: 1. Transformer T1 should
DD
10 F
1N4150,
V
2. Lead "b" of termination 2
DD
a
Bias
b
have a passband of at least
300 kHz to 5 MHz.
shown above should be
connected to transformer
pin marked with polarity
dot.
Z
input pin are not needed to
T
V
V
DD
DD
40
1N4450,
MSAN-141
2 : 1
2 : 1
1N4148,
A-221