Datasheet

SCBA015A
7–37
Fast GTLP Backplanes With the GTLPH1655
The measurement results presented in Figures 29 through 52 show:
The LVTTL input signal of the SN74GTLPH1655 that drives the bus line, together with the
LVTTL output signal of the SN74GTLPH1655 receiver that is situated at the end of the GTLP
bus. For this, the load of the receiver was varied. The diagrams show the curves for
R
L
= (unloaded output) and for R
L
= 50 .
Waveforms on the GTLP bus line:
GTLP output signal of the SN74GTLPH1655 that drives the bus line, i.e., the signal at
the beginning of the line
Bus signal in the middle of the GTLP bus
Signal at the end of the GTLP bus line, which also is applied to the input of the
SN74GTLPH1655 receiver device.
All curves are shown together for the frequencies 10 MHz, 50 MHz, and 160 MHz, and for the
two different edge-rate settings (with ERC = V
CC
and ERC = GND).
For these measurements, care was taken to ensure that the timing relationships between them
remained constant. A summary of the measurement results is given in Table 7.
Table 7. Measurement Results on SN74GTLPH1655 Demonstration Board
BUS LINE UNLOADED
(WITHOUT CAPACITORS)
BUS LINE LOADED
(WITH CAPACITORS)
SIGNAL
SLOW
EDGE RATE
ERC = V
CC
FAST
EDGE RATE
ERC = GND
SLOW
EDGE RATE
ERC = V
CC
FAST
EDGE RATE
ERC = GND
f=10MHz
I/O LVTTL level Figure 29 Figure 31 Figure 41 Figure 43
f
=
10
MH
z
Beginning, middle, end of GTLP bus Figure 30 Figure 32 Figure 42 Figure 44
f=50MHz
I/O LVTTL level Figure 33 Figure 35 Figure 45 Figure 47
f
=
50
MH
z
Beginning, middle, end of GTLP bus Figure 34 Figure 36 Figure 46 Figure 48
f =160 MHz
I/O LVTTL level Figure 37 Figure 39 Figure 49 Figure 51
f
=
160
MH
z
Beginning, middle, end of GTLP bus Figure 38 Figure 40 Figure 50 Figure 52