Datasheet
SCEA019 - January 2001
7–76 Texas Instruments GTLP Frequently Asked Questions
Table of Contents
Introduction............................................................................................................................ 7–78
1. What is a backplane?............................................................................................................. 7–78
2. What is a backplane protocol? ............................................................................................... 7–78
3. Should I use a parallel or serial architecture?......................................................................... 7–78
4. If I use a parallel single-ended backplane, why do I need to use backplane-optimized
transceivers and not just typical LVT or FCT devices?........................................................... 7–79
5. What is VME?........................................................................................................................ 7–79
6. What is GTL?......................................................................................................................... 7–80
7. What is the difference between GTLP and GTL?................................................................... 7–83
8. What is distributed capacitance?............................................................................................ 7–86
9. What are you going to do with GTL now that you have GTLP? .............................................. 7–89
10. How should I terminate GTL devices in short-distance applications? ..................................... 7–90
11. What is the advantage of using GTLP in my backplane? ....................................................... 7–90
12. What is the difference between GTLP and LVDS?................................................................. 7–92
13. How does GTLP compare to other single-ended and differential bus solutions?.................... 7–93
14. What is the maximum data throughput using GTLP? ............................................................. 7–95
15. What is the difference between synchronous clock and source-synchronous clock? ............. 7–97
16. What GTLP devices are available and how much will they cost? ........................................... 7–98
17. These function numbers are different. How do they compare to normal logic functions?........ 7–99
18. I know what a bus transceiver is, but what is a UBT? ........................................................ 7–100
19. I need an alternate source. Are there any? .......................................................................... 7–102
20. Are the alternate-source devices identical?.......................................................................... 7–103
21. What is important about live insertion?................................................................................. 7–104
22. What is the total power consumption of an 18-bit GTLP driver?........................................... 7–105
23. How should I generate the termination voltage?................................................................... 7–108
24. Why not use Thevenin voltage dividers for termination? ...................................................... 7–109
25. Tell me more about bus hold................................................................................................ 7–110
26. Tell me more about power-up 3-State (PU3S). .................................................................... 7–110
27. Should I tie GTLPH16612 control inputs to 3.3 V or to 5 V? ................................................ 7–110
28. What do I do with unused or undriven GTLP A- or B-port I/Os? ........................................... 7–111
29. Can I connect the SN74GTLPH16612GR unused I/O pins of the
A ports and B ports directly to GND? .................................................................................. 7–112
30. How does an extender card affect signal integrity? .............................................................. 7–112
31. What is the transistor count for GTLP devices?.................................................................... 7–113
32. Can I use GTLP as a low-voltage translator?....................................................................... 7–114
33. What is the voltage input range I can apply to the B port if V is set at 0.8 V?................... 7–116
34. Can I use GTLP as a replacement for FB+ devices?............................................................ 7–116
35. I’m trying to determine which 3.3-V logic family will best fit my needs, and
I’m still not quite clear on what choice I should make. ......................................................... 7–117
36. How do I get a GTLP data sheet?........................................................................................ 7–119
37. When will GTLP models and devices be available? ............................................................. 7–119