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DS8921/DS8921A/DS8921AT
Differential Line Driver and Receiver Pair
General Description
The DS8921, DS8921A are Differential Line Driver and Receiver pairs designed specifically for applications meeting
the ST506, ST412 and ESDI Disk Drive Standards. In addition, these devices meet the requirements of the EIA Standard RS-422.
The DS8921, DS8921A receivers offer an input sensitivity of
200 mV over a
±
7V common mode operating range. Hysteresis is incorporated (typically 70 mV) to improve noise margin for slowly changing input waveforms.
The DS8921, DS8921A drivers are designed to provide unipolar differential drive to twisted pair or parallel wire transmission lines. Complementary outputs are logically ANDed
and provide an output skew of 0.5 ns (typ.) with propagation
delays of 12 ns.
The DS8921, DS8921A are designed to be compatible with
TTL and CMOS.
Features
n 12 ns typical propagation delay
n Output skew - 0.5 ns typical
n Meet the requirements of EIA Standard RS-422
n Complementary Driver Outputs
n High differential or common-mode input voltage ranges
of
±
7V
n
±
0.2V receiver sensitivity over the input voltage range
n Receiver input hysteresis-70 mV typical
n DS8921AT industrial temperature
operation: (−40˚C to +85˚C)
Connection Diagram
Truth Table
Receiver Driver
Input V
OUT
Input V
OUTVOUT
VID≥ VTH(MAX) 1 1 1 0
V
ID
≤ VTH(MIN) 0 0 0 1
Open 1
DS008512-1
Order Number DS8921M, DS8921N, DS8921AM, DS8921AN,
DS8921ATM, or DS8921ATN
See NS Package Number M08A or N08E
May 1998
DS8921/DS8921A/DS8921AT Differential Line Driver and Receiver Pair
© 1998 National Semiconductor Corporation DS008512 www.national.com
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage 7V
Driver Input Voltage −0.5V to +7V
Output Voltage 5.5V
Receiver Output Sink
Current 50 mA
Receiver Input Voltage
±
10V
Differential Input Voltage
±
12V
Maximum Package Power Dissipation
@
+25˚C
M Package 730 mW
N Package 1160 mW
Derate M Package 9.3 mW/˚C above +25˚C
Derate N Package 5.8 mW/˚C above +25˚C
Storage Temperature
Range −65˚C to +165˚C
Lead Temperature +260˚C
(Soldering, 4 sec.) +260˚C
Maximum Junction
Temperature +150˚C
Recommended Operating
Conditions
Min Max Units
Supply Voltage 4.5 5.5 V
Temperature (T
A
)
DS8921/DS8921A 0 70 ˚C
DS8921AT −40 +85 ˚C
DS8921/DS8921A Electrical Characteristics (Notes 2, 3, 4)
Symbol Conditions Min Typ Max Units
RECEIVER
V
TH
−7V ≤ VCM≤ +7V −200
±
35 +200 mV
V
HYST
−7V ≤ VCM≤ +7V 15 70 mV
R
IN
V
IN
=
−7V, +7V 4.0 6.0 kΩ
(Other Input=GND)
I
IN
V
IN
=
10V 3.25 mA
V
IN
=
−10V −3.25 mA
V
OH
I
OH
=
−400 µA 2.5 V
V
OL
I
OL
=
8 mA 0.5 V
I
SC
V
CC
=
MAX, V
OUT
=
0V −15 −100 mA
DRIVER
V
IH
2.0 V
V
IL
0.8 V
I
IL
V
CC
=
MAX, V
IN
=
0.4V −40 −200 µA
I
IH
V
CC
=
MAX, V
IN
=
2.7V 20 µA
I
I
V
CC
=
MAX, V
IN
=
7.0V 100 µA
V
CL
V
CC
=
MIN, I
IN
=
−18 mA −1.5 V
V
OH
V
CC
=
MIN, I
OH
=
−20 mA 2.5 V
V
OL
V
CC
=
MIN, I
OL
=
+20 mA 0.5 V
I
OFF
V
CC
=
0V, V
OUT
=
5.5V 100 µA
|V
T
| – |VT | 0.4 V
V
T
2.0 V
|V
OS–VOS
| 0.4 V
I
SC
V
CC
=
MAX, V
OUT
=
0V −30 −150 mA
DRIVER and RECEIVER
I
CC
V
CC
=
MAX, V
OUT
=
Logic 0 35 mA
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Receiver Switching Characteristics
Figure 1(Figure 2
)
Symbol Conditions Min Typ Max Units
8921 8921A 8921AT
T
pLH
C
L
=
30 pF 14 22.5 20 20 ns
(
Figures 1, 2
)
T
pHL
C
L
=
30 pF 14 22.5 20 20 ns
(
Figures 1, 2
)
|T
pLH–TpHL
|C
L
=
30 pF 0.5 5 3.5 5 ns
(
Figures 1, 2
)
Driver Switching Characteristics
SINGLE ENDED CHARACTERISTICS (
Figures 3, 4
)
Symbol Conditions Min Typ Max Units
8921 8921A 8921AT
T
pLH
C
L
=
30 pF 10 15 15 15 ns
(
Figures 3, 4
)
T
pHL
C
L
=
30 pF 10 15 15 15 ns
(
Figures 3, 4
)
T
TLH
C
L
=
30 pF 5 8 8 9.5 ns
(
Figures 7, 8
)
T
THL
C
L
=
30 pF 5 8 8 9.5 ns
(
Figures 7, 8
)
Skew CL=30 pF 1 5 3.5 3.5 ns
(
Figures 3, 4
)
Driver Switching Characteristics(Note 6)
DIFFERENTIAL CHARACTERISTICS (
Figures 3, 5
)
Symbol Conditions Min Typ Max Units
8921 8921A 8921AT
T
pLH
C
L
=
30 pF 10 15 15 15 ns
(
Figures 3, 5, 6
)
T
pHL
C
L
=
30 pF 10 15 15 15 ns
(
Figures 3, 5, 6
)
|T
pLH–TpHL
|C
L
=
30 pF 0.5 6 2.75 2.75 ns
(
Figures 3, 5, 6
)
Note 1: “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the device
should be operated at these limits. The Table of “Electrical Characteristics” provides conditions for actual device operation.
Note 2: All currents into device pins areshownas positive values; all currents out of the device are shown as negative; all voltages are referenced to ground unless
otherwise specified. All values shown as max or min are classified on absolute value basis.
Note 3: All typical values are V
CC
=
5V, T
A
=
25˚C.
Note 4: Only one output at a time should be shorted.
Note 5: Difference between complementary outputs at the 50%point.
Note 6: Differential Delays are defined as calculated results from single ended rise and fall time measurements.This approach in establishingAC performance speci-
fications has been taken due to limitations of available Automatic Test Equipment (ATE).
The calculated ATE results assume a linear transition between measurement points and are a result of the following equations:
Where: T
cr
=
Crossing Point
T
ra,Trb,Tfa
and Tfbare time measurements with respect to the input. See
Figure 6
.
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AC Test Circuits and Switching Diagrams
DS008512-3
FIGURE 1.
DS008512-4
FIGURE 2.
DS008512-5
FIGURE 3.
DS008512-6
FIGURE 4.
DS008512-7
FIGURE 5.
DS008512-2
FIGURE 6.
DS008512-10
FIGURE 7.
DS008512-11
FIGURE 8.
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Typical Applications
ST506 and ST412 Application
DS008512-8
ESDI Application
DS008512-9
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6
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Physical Dimensions inches (millimeters) unless otherwise noted
SO Package (M)
Order Number DS8921M, DS8921AM or DS8921ATM
NS Package Number M08A
Molded Dual-In-Line Package (N)
Order Number DS8921N, DS8921AN or DS8921ATN
NS Package Number N08E
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LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into
the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance
with instructions for use provided in the labeling, can
be reasonably expected to result in a significant injury
to the user.
2. A critical component in any component of a life support
device or system whose failure to perform can be reasonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
National Semiconductor
Corporation
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: support@nsc.com
www.national.com
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Email: europe.support@nsc.com
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Tel: 65-2544466
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Japan Ltd.
Tel: 81-3-5620-6175
Fax: 81-3-5620-6179
DS8921/DS8921A/DS8921AT Differential Line Driver and Receiver Pair
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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