SN74F1056
8-BIT SCHOTTKY BARRIER DIODE
BUS-TERMINATION ARRAY
SDFS085A – AUGUST 1992 – REVISED JUL Y 1997
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
D
Designed to Reduce Reflection Noise
D
Repetitive Peak Forward Current 300 mA
D
8-Bit Array Structure Suited for
Bus-Oriented Systems
description
This Schottky barrier diode bus-termination array
is designed to reduce reflection noise on memory
bus lines. This device consists of an 8-bit
high-speed Schottky diode array suitable for a
clamp to GND.
The SN74F1056 is characterized for operation
from 0°C to 70°C.
schematic diagrams
1
2
3
4
7
8
9
10
1
2
3
4
5
6
7
8
6
5
15
14
13
12
11
10
GND
GND
GND
GND
GND
GND
GND
GND
D01
D02
D03
D04
D05
D06
D07
D08
D01
D02
D03
D04
D05
D06
D07
D08
SC Package D Package
Copyright 1997, Texas Instruments Incorporated
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.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
SC PACKAGE
(TOP VIEW)
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
D01
D02
D03
D04
D05
D06
D07
D08
NC
GND
GND
GND
GND
GND
GND
NC
D PACKAGE
(TOP VIEW)
1
2
3
4
5
6
7
8
9
10
D01
D02
D03
D04
GND
GND
D05
D06
D07
D08
SN74F1056
8-BIT SCHOTTKY BARRIER DIODE
BUS-TERMINATION ARRAY
SDFS085A – AUGUST 1992 – REVISED JUL Y 1997
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
†
Steady-state reverse voltage, V
R
7 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous forward current, I
F
: Any D terminal from GND 50 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Total through all GND terminals 170 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repetitive peak forward current, I
FRM
(see Note 1): 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, T
stg
–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 affect device reliability.
NOTE 1: 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 2)
PARAMETER TEST CONDITIONS MIN TYP‡MAX UNIT
I
R
Static reverse current VR = 7 V 2 µA
IF = 18 mA 0.8 1
VFStatic forward voltage
IF = 50 mA 1 1.2
V
V
FM
Peak forward voltage IF = 200 mA 1.23 V
p
VR = 0, f = 1 MHz 3 3.75
p
CtTotal capacitance
VR = 2 V, f = 1 MHz 2.5 3
pF
‡
All typical values are at TA = 25°C.
NOTE 2: T est 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
I
x
Internal crosstalk current Total GND current = 1.2 A, See Note 3 10 50 µA
‡
All typical values are at TA = 25°C.
NOTE 3: 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 Ix.
switching characteristics, TA = 25°C
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
t
rr
Reverse recovery time IF = 10 mA, I
RM(REC)
= 10 mA, I
R(REC)
= 1 mA, RL = 100 Ω 5 7 ns
undershoot characteristics
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
V
US
Undershoot voltage
tf = 2 ns, tw = 50 ns, VIH = 5 V, VIL = 0, ZS = 25 Ω, ZO = 50 Ω,
L = 36-inch coax
0.6 0.7 V
SN74F1056
8-BIT SCHOTTKY BARRIER DIODE
BUS-TERMINATION ARRAY
SDFS085A – AUGUST 1992 – REVISED JUL Y 1997
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 SN74F1056 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 reduce negative transients, but they also can 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 the following figures. The diode
conducts current when 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 versus
voltage plot for the SN74F1056 is shown in Figure 1.
To illustrate how the diode arrays act to reduce negative transients at the end of a transmission line, the test setup
in Figure 2(a) was evaluated. The resulting waveforms with and without the diode are shown in Figure 2(b).
The maximum effectiveness of the diode arrays in suppressing negative transients occurs when the diode arrays are
placed at the end of a line and/or the end of a long stub branching off a main transmission line. The diodes also can
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.
– Forward Current – mA
VF – Forward Voltage – V
I
I
Variable 1:
V
IN
–Ch 1
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
DIODE FORWARD CURRENT
vs
DIODE FORWARD VOLTAGE
–50
–40
–20
–10
0
–90
–30
0 0.2 0.4 0.6 0.8 1 1.2
–70
–60
–80
–100
1.4 1.6 1.8 2
TA = 25°C
Figure 1. Current Versus Voltage for the SN74F1056
SN74F1056
8-BIT SCHOTTKY BARRIER DIODE
BUS-TERMINATION ARRAY
SDFS085A – AUGUST 1992 – REVISED JUL Y 1997
4
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
ZO = 50 Ω
Length = 36 in.
(a) UNDERSHOOT TEST SETUP
ZS = 25Ω
1.03610 µs
Ch 1 = 2.000 V/div
Timebase = 5.00 ns/div
Vmarker 1 = 0.0000 V
Vmarker 2 = –600.00 mV
Offset = 2.340 V
Delay = 1.06110 µs
Delta V = –600.0 mV
1.06110 µs 1.08610 µs
–2.6 V
Vmarker 1
Vmarker 2
(b) OSCILLOSCOPE DISPLAY
S1
S1 Open
S1 Closed
Figure 2. Undershoot Test Setup and Oscilloscope Display
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Copyright 1998, Texas Instruments Incorporated
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