DS78C20/DS88C20
Dual CMOS Compatible Differential Line Receiver
General Description
The DS78C20 and DS88C20 are high performance, dual dif-
ferential, CMOS compatible line receivers for both balanced
and unbalanced digital data transmission. The inputs are
compatible with EIA and Federal Standards.
Input specifications meet or exceed those of the popular
DS7820/DS8820 line receiver, and the pinout is identical.
A response pin is provided for controlling sensitivity to input
noise spikes with an external capacitor. Each receiver in-
cludes a 180
terminating resistor, which may be used op-
tionally on twisted pair lines. The DS78C20 is specified over
a -55C to +125C operating temperature range, and the
DS88C20 over a 0C to +70C range.
Features
n
Meets requirements of EIA Standards RS-232-C RS-422
and RS-423, and Federal Standards 1020 and 1030
n
Input voltage range of
15V (differential or
common-mode)
n
Separate strobe input for each receiver
n
1
/
2
V
CC
strobe threshold for CMOS compatibility
n
5k typical input impedance
n
50 mV input hysteresis
n
200 mV input threshold
n
Operation voltage range = 4.5V to 15V
n
DS7830/DS8830 recommended driver
Connection Diagram
Dual-In-Line Package
DS005798-1
Top View
Order Number DS88C20N
See NS Package Numbers N14A
For Complete Military Product Specifications,
refer to the appropriate SMD or MDS.
Order Number DS78C20J/883
See NS Package Number J14A
May 1998
DS78C20/DS88C20
Dual
CMOS
Compatible
Differential
Line
Receiver
1998 National Semiconductor Corporation
DS005798
www.national.com
Absolute Maximum Ratings
(Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
18V
Common-Mode Voltage
25V
Differential Input Voltage
25V
Strobe Voltage
18V
Output Sink Current
50 mA
Maximum Power Dissipation (Note 1) at 25C
Cavity Package
1364 mW
Molded Package
1280 mW
Storage Temperature Range
-65C to
+150C
Lead Temperature (Soldering, 4 seconds)
260C
Operating Conditions
Min
Max
Units
Supply Voltage (V
CC
)
4.5
15
V
Temperature (T
A
)
DS78C20
-55
+125
C
DS88C20
0
+70
C
Common-Mode Voltage (V
CM
)
-15
+15
V
Note 1: Derate cavity package 9.1 mW/C; derate molded package 10.2
mW/C above 25C.
Electrical Characteristics
(Notes 3, 4)
Symbol
Parameter
Conditions
Min
Typ
Max Units
V
TH
Differential Threshold
I
OUT
= -200 A,
-10V
V
CM
10V
0.06
0.2
V
Voltage
V
OUT
V
CC
-1.2V
-15V
V
CM
15V
0.06
0.3
V
I
OUT
= 1.6 mA, V
OUT
0.5V
-10V
V
CM
10V
-0.08
-0.2
V
-15V
V
CM
15V
-0.08
-0.3
V
R
IN
Input Resistance
-15V
V
CM
15V
5
k
R
T
Line Termination
Resistance
T
A
= 25C
100
180
300
I
IND
Data Input Current
V
CM
= 10V
2
3.1
mA
(Unterminated)
V
CM
= 0V
0
-0.5
mA
V
CM
= -10V
-2
-3.1
mA
V
THB
Input Balance
I
OUT
= 200 A, V
OUT
-7V
V
CM
7V
V
CC
-1.2V, R
S
= 500
,
0.1
0.4
V
(Note 6)
I
OUT
= 1.6 mA, V
OUT
0.5V,
-7V
V
CM
7V
-0.1
-0.4
V
R
S
= 500
, (Note 6)
V
OH
Logical "1" Output Voltage
I
OUT
= -200 A, V
DIFF
= 1V
V
CC
-1.2
V
CC
-0.75
V
V
OL
Logical "0" Output Voltage
I
OUT
= 1.6 mA, V
DIFF
= -1V
0.25
0.5
V
I
CC
Power Supply Current
15V
V
CM
-15V,
V
CC
= 5.5V
8
15
mA
V
DIFF
= -0.5V
V
CC
= 15V
15
30
mA
(Both Receivers)
I
IN(1)
Logical "1" Strobe Input
Current
V
STROBE
= 15V, V
DIFF
= 3V
V
CC
= 15V
15
100
A
I
IN(0)
Logical "0" Strobe Input
Current
V
STROBE
= 0V, V
DIFF
= -3V
V
CC
= 15V
-0.5
-100
A
V
IH
Logical "1" Strobe Input
I
OUT
= 1.6 mA, V
OL
0.5V
V
CC
= 5V
3.5
2.5
V
Voltage
V
CC
= 10V
8.0
5.0
V
V
CC
= 15V
12.5
7.5
V
V
IL
Logical "0" Strobe Input
I
OUT
= -200 A,
V
CC
= 5V
2.5
1.5
V
Voltage
V
OH
= V
CC
-1.2V
V
CC
= 10V
5.0
2.0
V
V
CC
= 15V
7.5
2.5
V
I
OS
Output Short-Circuit
Current
V
OUT
= 0V, V
CC
= 15V, V
STROBE
= 0V, (Note 5)
-5
-20
-40
mA
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2
Switching Characteristics
V
CC
= 5V, T
A
= 25C
Symbol
Parameter
Conditions
Min
Typ
Max
Units
t
pd0(D)
Differential Input to "0" Output
C
L
= 50 pF
60
100
ns
t
pd1(D)
Differential Input to "1" Output
C
L
= 50 pF
100
150
ns
t
pd0(S)
Strobe Input to "0" Output
C
L
= 50 pF
30
70
ns
t
pd1(S)
Strobe Input to "1" Output
C
L
= 50 pF
100
150
ns
Note 2: "Absolute Maximum Ratings" are those values beyond which the safety of the device cannot be guaranteed. Except for "Operating Temperature Range" they
are not meant to imply that the devices should be operated at these limits. The table of "Electrical Characteristics" provides conditions for actual device operation.
Note 3: Unless otherwise specified min/max limits apply across the -55C to +125C temperature range for the DS78C20 and across the 0C to +70C range for the
DS88C20. All typical values are for T
A
= 25C, V
CC
= 5V and V
CM
= 0V.
Note 4: All currents into device pins shown as positive, out of device pins as negative, all voltages referenced to ground unless otherwise noted. All values shown
as max or min on absolute value basis.
Note 5: Only one output at a time should be shorted.
Note 6: Refer to EIA-RS-422 for exact conditions.
Typical Applications
Note 7: (Optional internal termination resistor.)
a) Capacitor in series with internal line termination resistor, terminates the line and saves termination power. Exact value depends on line length.
b) Pin 1 connected to pin 2; terminates the line.
c) Pin 2 open; no internal line termination.
d) Transmission line may be terminated elsewhere or not at all.
Note 8: Optional to control response time.
Note 9: V
CC
4.5V to 15V for the DS78C20. For further information on line drivers and line receivers, refer to applicaton notes AN-22, AN-83 and AN-108.
RS-422/RS-423 Application
DS005798-2
RS-232-C Application with Hysteresis
DS005798-3
For signals which require fail-safe or have slow rise and fall times, use R1
and D1 as shown above. Otherwise, the positive input (pin 3 or 11) may be
connected to ground.
DS005798-4
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3
Typical Applications
(Continued)
V
CC
R1
5%
5V
4,3 k
10V
15 k
15V
24 k
AC Test Circuit
Switching Time Waveforms
DS005798-5
t
r
= t
f
=
10 ns
PRR = 1 MHz
Note 10: Includes probe and jig capacitance
DS005798-6
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4
Physical Dimensions
inches (millimeters) unless otherwise noted
Ceramic Dual-In-Line Package (J)
Order Number DS78C20J/883
NS Package Number J14A
Molded Dual-In-Line Package (N)
Order Number DS88C20N
NS Package Number N14A
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5
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