PE-65793 Datasheet, PDF (5/7 Pages) Pulse A Technitrol Company – ISDN S-Interface Transformers

ISDN S-Interface Transformers
Surface Mount, Dual, 2000Vrms
HP-8751A
Network Analyzer
Out R A B
ISM-1 = Wandel and Goltermann
Signal Balance Ratio Bridge
VT
EL
ISM-1
Pri
Sec
Terminating
Resistor
Figure 2. Longitudinal Balance Test Circuit
2. (continued from previous page) A recommended
test set up is shown in Figure 2. A high inductance “low
frequency” is common mode choke, such as PE-
65950NL or PE-65853NL, is recommended to improve
balance, or to correct inherent unbalances of some
circuits.
3. Impedance Requirements - The requirements for
minimum impedance in the inactive and powered-
down states are expressed by impedance templates
for both transmitter and receiver in NT and TE. At the
low frequency end of 1MHz, it is reasonable to
assume that the impedance seen from the line is
entirely capacitive. The maximum capacitance budget,
derived from the templates, is somewat different
for the NT and the TE. Contributors to the total
capacitance are: the chip output, the protection circuit,
the transformer, common mode choke, and any other
element that may be present. In the TE case, there is
also the maximum allowable TE cord impedance. Here
the maximum buget is 800pF. As a rule, the
capacitances should be kept as low as possible in the
interface circuit design. With the specified transformer
capacitances, it is possible to remain within budget
and have a reasonable margin for measurement errors.
4. Common Mode Chokes - The “high frequency” 4-wire
common mode chokes shown on pages 7 and 8
provide an effective means of compliance with national
and international regulations on EMI. They are designed
to be used in conjunction with either Pulse’s ISDN
S-Interface or T1/CEPT transformers as shown in Figure
1. A high inductance “low frequency” common mode
choke is recommended to improve balance, or to
correct inherent unbalances of some ISDN S-Interface
circuits.
5. Surge Voltage Capability for Transformers and
Chokes
•Longitudinal Voltage Peak: 2,400V 10/700μsec
•Metallic Voltage Peak:800V10/560μsec
6. Behavior Under Fault Conditions - Telephony voltages
may accidentally appear on the ISDN S-Interface line
to the transformer. The transformer will withstand a
DC current of 0.5 Amps for 15 minues without
permanent damage. Such current may be cauased by
the telephone central battery. The transformer will
also survive ringing voltages. These are nominally
120V or 200V maximum at 20 to 60Hz, limited by
1500W resistive or 400 to 600W inductive limiting.
These may cause peak currents.
7. Flammability - Materials used in the products are
recognized UL94-VO. Products meet the requirements
of IEC 695-2-2 (Needle Flame Test).
5
pulseelectronics.com
T604.F (05/12)