Datasheet

SN74GTLPH1645
16-BIT LVTTL-TO-GTLP ADJUSTABLE-EDGE-RATE BUS TRANSCEIVER
SCES290D – OCTOBER 1999 – REVISED SEPTEMBER 2001
3–122
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
DISTRIBUTED-LOAD BACKPLANE SWITCHING CHARACTERISTICS
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.
Drvr
1.5 V
.25” 1”
1” 1”
1.5 V
1”1”
1” .25”
Rcvr
Rcvr
Rcvr
Figure 2. High-Drive Test Backplane
Slot 1 Slot 2 Slot 19 Slot 20
Conn.
Conn. Conn. Conn.
Z
O
= 50 Ω
22 Ω 22 Ω
From Output
Under Test
Test
Point
1.5 V
C
L
= 18 pF
11 Ω
L
L
= 14 nH
Figure 3. High-Drive RLC Network
switching characteristics 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)
PARAMETER
FROM
(INPUT)
TO
(OUTPUT)
EDGE RATE
†
TYP
‡
UNIT
t
PLH
4.9
t
PHL
A B Slow
4.9
ns
t
PLH
3.7
t
PHL
A B Fast
3.7
ns
t
en
5.1
t
dis
OE
B Slow
5.4
ns
t
en
4.1
t
dis
OE
B Fast
4.1
ns
Slow 2
t
r
Rise time, B outputs (20% to 80%)
Fast 1.2
ns
Slow 2.5
t
f
Fall time, B outputs (80% to 20%)
Fast 1.8
ns
†
Slow (ERC
= GND) and Fast (ERC = V
CC
)
‡
All typical values are at V
CC
= 3.3 V, T
A
= 25°C. All values are derived from TI-SPICE models.