SN74F1018
18-BIT SCHOTTKY BARRIER DIODE
R-C BUS-TERMINATION ARRAY
SDFS094 – NOVEMBER 1992 – REVISED DECEMBER 1993
Copyright 1993, Texas Instruments Incorporated
2–1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
•Designed to Reduce Reflection Noise
•Repetitive Peak Forward
Current . . . 300 mA
•18-Bit Array Structure Suited for
Bus-Oriented Systems
description
This bus-termination array is designed to reduce
reflection noise and minimize ringing on
high-performance bus lines. The SN74F1018
features an 18-bit R-C network and Schottky
barrier diode array. These Schottky diodes
provide clamp-to-ground functionality and serve
to minimize overshoot and undershoot of
high-speed switching buses.
The SN74F1018 is characterized for operation
from 0°C to 70°C.
schematic diagram
GND A18 A17 A16 A15 A14 A13 A12 A11
GND A1 A2 A3 A4 A5 A6 A7 A8
GND
GND
GND
GND
23 22 21 20 19 18 17 16 1524 13
23 4 5 6 7 8 9 101 12
A10
A9
14
11
Resistor = 50 Ω ± 10%
Capacitor = 47 pF ± 10%, VR = 2.5 V, f = 1 MHz
Diode = Schottky
DW PACKAGE
(TOP VIEW)
1
2
3
4
5
6
7
8
9
10
11
12
GND
GND
A1
A2
A3
A4
A5
A6
A7
A8
A9
GND
GND
GND
A18
A17
A16
A15
A14
A13
A12
A11
A10
GND
24
23
22
21
20
19
18
17
16
15
14
13
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
SN74F1018
18-BIT SCHOTTKY BARRIER DIODE
R-C BUS-TERMINATION ARRAY
SDFS094 – NOVEMBER 1992 – REVISED DECEMBER 1993
2–2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†
Steady-state reverse voltage, VR 7 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous forward current, IF: Any D terminal from GND 50 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Total through all GND terminals 170 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repetitive peak forward current, IFRM‡: Any D terminal from GND 300 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Total through all GND terminals 1.2 A. . . . . . . . . . . . . . . . . . . . . . . . .
Continuous total power dissipation at (or below) 25°C free-air temperature 500 mW. . . . . . . . . . . . . . . . . . . .
Operating free-air temperature range 0°C to 70°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range –65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
†Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may af fect device reliability.
‡These values apply for tw ≤ 100 µs, duty cycle ≤ 20%.
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
single-diode operation (see Note 1)
PARAMETER TEST CONDITIONS MIN TYP†MAX UNIT
IRStatic reverse current VR = 7 V 2 µA
VF
Static forward voltage
IF = 18 mA 0.8 1
V
V
F
Static
for
w
ard
v
oltage
IF = 50 mA 1 1.2
V
VFM Peak forward voltage IF = 200 mA 1.25 V
VR = 0 80
CtTotal capacitance VR = 2 V 60 pF
VR = 3 V 55
†All typical values are at TA = 25°C.
NOTE 1: Test conditions and limits apply separately to each of the diodes. The diodes not under test are open-circuited during the measurement
of these characteristics.
multiple-diode operation
PARAMETER TEST CONDITIONS MIN TYP†MAX UNIT
IxInternal crosstalk current Total GND current = 1.2 A, See Note 2 10 50 µA
NOTE 2: Ix is measured under the following conditions with one diode static, all others switching:
Switching diodes: tw = 100 µs, duty cycle = 20%;
Static diode: VR = 5 V; the static diode input current is the internal crosstalk current I x.
switching characteristics, TA = 25°C
PARAMETER TEST CONDITIONS MIN TYP†MAX UNIT
trr Reverse recovery time IF = 10 mA, IRM(REC) = 10 mA, IR(REC) = 1 mA, RL = 100 Ω8 10 ns
undershoot characteristics
PARAMETER TEST CONDITIONS MIN TYP†MAX UNIT
VUS Undershoot voltage tf = 2 ns, tw = 50 ns, VIH = 5 V, VIL = 0, ZS = 25 Ω, Z O = 50 Ω,
L = 36-inch coaxial cable 0.7 0.8 V
SN74F1018
18-BIT SCHOTTKY BARRIER DIODE
R-C BUS-TERMINATION ARRAY
SDFS094 – NOVEMBER 1992 – REVISED DECEMBER 1993
2–3
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
Large negative transients occurring at the inputs of memory devices (DRAMs, SRAMs, EPROMs, etc.) or on the
CLOCK lines of many clocked devices can result in improper operation of the devices. The SN74F1018 diode
termination array helps suppress negative transients caused by transmission line reflections, crosstalk, and switching
noise.
Diode terminations have several advantages when compared to resistor termination schemes. Split resistor or
Thevenin equivalent termination can cause a substantial increase in power consumption. The use of a single resistor
to ground to terminate a line usually results in degradation of the output high level, resulting in reduced noise immunity.
Series damping resistors placed on the outputs of the driver will reduce negative transients, but they can also increase
propagation delays down the line, as a series resistor reduces the output drive capability of the driving device. Diode
terminations have none of these drawbacks.
The operation of the diode arrays in reducing negative transients is explained in Figure 1. The diode conducts current
whenever the voltage reaches a negative value large enough for the diode to turn on. Suppression of negative
transients is tracked by the current-voltage characteristic curve for that diode. A typical current voltage for the
SN74F1018 is shown in Figure 1.
The maximum effectiveness of the diode arrays in suppressing negative transients occurs when they are placed at
the end of a line and/or the end of a long stub branching off a main transmission line. The diodes can also be used
to reduce the negative transients that occur due to discontinuities in the middle of a line. An example of this is a slot
in a backplane that is provided for an add-on card.
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
– Forward Current – mA
VF – Forward Voltage – V
TA = 25°C
II
Variable 1:
VIN –Ch1
Linear Sweep:
Start 0.000 V
Stop –2.000 V
Step – 0.010 V
Constants:
VHI –Vs1 3.5000 V
VLO –Vs2 0.0000 V
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
DIODE FORWARD CURRENT
vs
DIODE FORWARD VOLTAGE
Figure 1
SN74F1018
18-BIT SCHOTTKY BARRIER DIODE
R-C BUS-TERMINATION ARRAY
SDFS094 – NOVEMBER 1992 – REVISED DECEMBER 1993
2–4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
ZO = 50 Ω
Length = 36 in
(a) UNDERSHOOT TEST SETUP
ZS = 25Ω
218.500 ns
Ch. 1 = 1.00 V/div
Timebase = 5.00 ns/div
Vmarker 1 = 0.00 V
Vmarker 2 = –640.00 mV
Offset = – 20.00 mV
Delay = 243.5 ns
Delta V = –640.00 mV
243.500 ns 268.500 ns
Vmarker 1
(b) SCOPE DISPLAY
S1
S1 Open
S1 Closed
Vmarker 2
–2.0 V
Figure 2. Undershoot Test Setup and Scope Display
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Copyright 1998, Texas Instruments Incorporated
