Datasheet

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Distributed-Load Backplane Switching Characteristics
From Output
Under Test
Test
Point
1.5 V
C
L
= 9 pF
19 Ω
L
L
= 19 nH
Drvr
1.5 V
0.25” 2”
1” 1”
1.5 V
1”1”
2” 0.25”
Rcvr
Rcvr
Rcvr
Slot 1 Slot 2 Slot 9 Slot 10
Conn.
Conn. Conn. Conn.
Z
O
= 70 Ω
38 Ω
38 Ω
Switching Characteristics
SN74GTLPH306
8-BIT LVTTL-TO-GTLP BUS TRANSCEIVER
SCES284E – OCTOBER 1999 – REVISED APRIL 2005
The preceding switching characteristics table shows the switching characteristics of the device into a lumped
load (Figure 1). However, the designer's backplane application probably is a distributed load. The physical
representation is shown in Figure 2. This backplane, or distributed load, can be approximated closely to a
resistor inductance capacitance (RLC) circuit, as shown in Figure 3. This device has been designed for optimum
performance in this RLC circuit. The following switching characteristics table shows the switching characteristics
of the device into the RLC load, to help the designer better understand the performance of the GTLP device in
this typical backplane. See www.ti.com/sc/gtlp for more information.
Figure 3. Medium-Drive RLC Network
Figure 2. Medium-Drive Test Backplane
over recommended ranges of supply voltage and operating free-air temperature,
V
TT
= 1.5 V and V
REF
= 1 V for GTLP (see Figure 3)
FROM TO
PARAMETER TYP
(1)
UNIT
(INPUT) (OUTPUT)
t
PLH
3.6
A B ns
t
PHL
4.1
t
en
4.4
OE B ns
t
dis
4.6
t
r
Rise time, B outputs (20% to 80%) 1.2 ns
t
f
Fall time, B outputs (80% to 20%) 2.2 ns
(1) All typical values are at V
CC
= 3.3 V, T
A
= 25°C. All values are derived from TI-SPICE models.
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