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Data Sheet
January 1998
T7256 Single-Chip NT1 (SCNT1) Transceiver
58
Lucent Technologies Inc.
Application Briefs
(continued)
T7256 Reference Circuit
(continued)
Table 29. T7256 Reference Schematic Parts List
(continued)
1. Kemet is a registered trademark of Kemet Laboratories Company, Inc.
2. Philips is a registered trademark of Philips Manufacturing Company.
3. Vitramon is a registered trademark of Vitramon, Inc.
4. Hewlett Packard is a registered trademark of Hewlett-Packard Company.
5. Polyswitch is a registered trademark of Raychem Corporation.
6. Bel and Bel Fuse are registered trademarks of Bel Fuse, Inc.
7. Molex is a registered trademark of Molex, Inc.
8. Pulse Engineering is a registered trademark of Pulse Engineering, Inc.
9. Dale is a registered trademark of Dale Electronics, Inc.
10.Valor is a registered trademark of Valor Electronics, Inc.
11.Advanced Power Components is a registered trademark of Advanced Power Technology, Inc.
12.Vacuumschmelze is a registered trademark of Vacuumschmelze GmbH.
13.SGS-Thomson is a registered trademark of SGS-Thomson Microelectronics, Inc.
14.Teccor is a registered trademark of Teccor, Inc.
15.MTRON is a registered trademark of MTRON Industries, Inc., a wholly owned subsidiary of Lynch* Corporation.
*
Lynch is a registered trademark of Lynch Corporation.
Note:
The Lucent 2754K2 and the Valor PT4084 have different winding resistances than the Lucent 2754H2, and therefore require a change
to the line-side resistor (R15). In addition, if the Bel Fuse is used in place of the Raychem TR600-150 PTC at location F1 (which will
sacrifice the resettable protection that the PTC provides), the line-side resistors must be adjusted to compensate for reduced resistance
due to the removal of the PTC (12
). The following table lists the necessary resistor values for these cases. Note that R15 is specified
at 1%. This is due to the fact that the values were chosen from standard 1% resistor tables. When a PTC is used, the overall tolerance
will be greater than 1%. This is acceptable, as long as the total line-side resistance is kept as close as possible to the ideal value. See
Question and Answer section, #6 for more details.
Table 30. Line-Side Resistor Requirements
Reference
Designator
VR1
Description
Source
Part #
Transient Voltage
Suppressor
SGS-
Thomson
13
SM6T6V8CA
Alternates:
Motorola SA6.5CA, P6KE6.8CA, P6KE7.5CA
SMP100-140
Alternate:
Teccor
14
P1602AB (972) 580-7777
1.5SMC6.8AT3
Alternate:
Motorola 1N6269A
SRX5144
Alternates:
MTRON
15
4044-001 (605) 665-9321
2B Elettronica S.D.L. TP0648 39-6-6622432
VR2
Transient Voltage
Suppressor
SGS-
Thomson
VR[3, 4]
Transient Voltage
Suppressor, 6.8 V
Motorola
X1
15.36 Crystal
Saronix
(415) 856-6900
Transformer
When Raychem TR600-150 Is Used
R13
21
15.4
9.53
0
When Bel Fuse Is Used
R13
33.2
27.4
21.5
10.7
Lucent 2754H2
Lucent 2754K2
Lucent 2809A
Valor PT4084