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contained therein.
HD26LS31
Quadruple Differential Line Drivers With 3 State Outputs
ADE-205-576 (Z)
1st. Edition
Dec. 2000
Description
The HD26LS31 features quadruple differential line drivers which satisfy the requirements of EIA standard
RS-422A. This device is designed to provide differential signals with high current capability on bus lines.
The circuit provides enable input to control all four drivers. The output circuit has active pull up and pull
down and is capable of sinking or sourcing 40 mA.
Logic Diagram
1A
2A
3A
4A
Enable G
Enable G
1Y
1Z
2Y
2Z
3Y
3Z
4Y
4Z
HD26LS31
2
Pin Arrangement
(Top view)
1
2
3
4
5
6
7
1A
GND
1Y
1Z
2Z
8
Enable G
2Y
2A
13
14
15
10
11
12
9
16 VCC
4A
4Y
4Z
Enable G
3Z
3Y
3A
Function Table
Input Enables Outputs
AG GYZ
HH X H L
LHXLH
HX L H L
LX L L H
XLHZZ
H : High level
L : Low level
X : Irrelevant
Z : High impedance (Off)
HD26LS31
3
Absolute Maximum Ratings
Item Symbol Ratings Unit
Supply Voltage VCC 7.0 V
Input Voltage VIN 7.0 V
Output Voltage VOUT 5.5 V
Power Dissipation PT1W
Storage Temperature Range Topr 0 to +70 °C
Lead Temperature Range Tstg –65 to +150 °C
Note: 1. The absolute maximum ratings are values which must not individually be exceeded, and
furthermore, no two of which may be realized at the same time.
Recommended Operating Conditions
Item Symbol Min Typ Max Unit Application Terminal
Supply Voltage VCC 4.75 5.0 5.25 V VCC
Output Current IOH — — –40 mA All Output
Output Current IOL — — 40 mA All Output
Operating Temperature Topr 0 25 70 — —
HD26LS31
4
Electrical Characteristics (Ta = 0 to +70°C)
Item Symbol Min Typ*1Max Unit Application
Terminal Conditions
Input Voltage VIH 2.0 — — V All Inputs
VIL — — 0.8
Input Clamp Voltage VIK — — –1.5 VCC = 4.75 V, II = –18 mA
Output Voltage VOH 2.5 — — All Outputs VCC = 4.75 V IOH = –20 mA
VOH — — 2.4 IOH = –40 mA
VOL — — 0.5 IOL = 40 mA
Output Current IOZL — — –20 mA VCC = 5.25 V VO = 0.5 V
IOZH — — 20 VCC = 5.25 V VO = 2.5 V
Input Current II— — 0.1 mA All Inputs VCC = 5.25 V VI = 7 V
IIH ——20µAV
I = 2.7 V
IIL — — –0.36 mA VI = 0.4 V
Short Circuit Output
Current IOS*2–30 — –150 All Outputs VCC = 5.25 V
Supply Current ICC —3280 V
CC VCC = 5.25 V
Notes: 1. All typical values are at VCC = 5 V, Ta = 25°C
2. Not more than one output should be shorted at a time and duration of the short circuit should not
exceed one second.
Switching Characteristics (VCC = 5 V, Ta = 25°C)
Item Symbol Min Typ Max Unit Application
terminal Test
circuit Conditions
Propagation Delay Time tPLH — 14 20 ns All Outputs 1 CL = 30 pF
tPHL —1420ns
Output Enable Time tZH —2540ns 2 C
L = 30 pF, RL = 75 Ω
tZL —3745ns 3 C
L = 30 pF, RL = 180 Ω
Output Disable Time tHZ —2130ns 2 C
L = 10 pF
tLZ —2335ns 3 C
L = 10 pF
Complementary Output To
Output Skew — 1 6 ns 1 CL = 30 pF
HD26LS31
5
Test Circuit 1
Output
Output
AZ
Y
Pulse Generator
PRR = 1MHz
Duty Cycle 50%
Zout = 50Ω
Input
G
G
4.5 V
C =
30 pF
L
C =
30 pF
L
Note: 1. CL includes probe and jig capacitance.
Waveforms
Input 0.3 V
2.7 V
1.3 V 0 V
3 V
1.3 V
Output Y
OH
VOL
V
tPHL
tPLH tPHL
1.5 V 1.5 V
1.5 V 1.5 V
VOH
VOL
Output Z
2.7 V
0.3 V
trtf
Skew tPLH
Skew
HD26LS31
6
Test Circuit 2
VCC
G
AY
Z
S1
Pulse Generator
PRR = 1 MHz
Duty Cycle 50%
Zout = 50Ω
G
Input
4.5 V Output
Output 180 Ω
180 Ω
75 Ω
S1
CL
75 Ω
CL
Note: 1. CL includes probe and jig capacitance.
Waveforms
Enable G
0.3 V
2.7 V
1.5 V 2.7 V
0 V
3 V
1.5 V 0.3 V
Enable G
Output
tZH
OH
V
1.5 V
tHZ
0.5 V
S1 Open
S1 : Closed
0 V
1.5 V
trtf
S1 : Open
HD26LS31
7
Test Circuit 3
VCC
G
AY
ZS2
Pulse Generator
PRR = 1 MHz
Duty Cycle 50%
Zout = 50Ω
G
Input
4.5 V Output
Output
180 Ω
75 Ω
CL
75 Ω
CL
180 Ω
S2
Note: 1. CL includes probe and jig capacitance.
Waveforms
Enable G
0.3 V
2.7 V
1.5 V 2.7 V
0 V
3 V
1.5 V 0.3 V
Enable G
Output
tZL
OL
V
1.5 V
tLZ
0.5 V
S2 : Open
4.5 V
1.5 V
trtf
S2 : Closed
HD26LS31
8
HD26LS31 Line Driver Applications
The HD26LS31 is a line driver that meets the EIA RS-422A conditions, and has been designed to supply a
high current for differential signals to a bus line. Its features are listed below.
• Operates on a single 5 V power supply.
• High output impedance when power is off
• Three-state output
• On-chip current limiter circuit
• Sink current and source current both 40 mA
A block diagram is shown in figure 1. The enable function is common to all four drivers, and either active-
high or active-low can be selected.
The output section consists of two output stages (the Y side and Z side), each of which has the same sink
current and source current capacity.
Input is TTL compatible, and an output current limiter circuit is built into the output stage as shown in
figure 2.
1A
2A
3A
4A
Enable G
Enable G
1Y
1Z
2Y
2Z
3Y
3Z
4Y
4Z
Figure 1 HD26LS31 Block Diagram
The output current limiter circuit consists of transistor Q1 and resistance R1, and operates when the voltage
drop on both sides of R1 reaches approximately 0.7 V. At this time the current, i, is as follows:
i = 0.7 (V) / 9 (Ω) ≈ 78 (mA)
When a current greater than this flows, Q1 is turned on, the Q2 base current flows to the output side, and the
flow of an excessively large output current is prevented.
However, since this type of current limiter circuit has the characteristics shown in figure 3, the output stage
power dissipation is large.
Therefore, when the output is shorted, this should be limited to a maximum of one second for one pin only.
The IOL vs. VOL characteristic for low-level output is shown in figure 4.
HD26LS31
9
An example of termination resistance connection when the HD26LS31 is used as a balanced differential
type driver is shown.
VCC
Output
Q3
R1
9 Ω
Q4
Q2
Q1
Figure 2 Output Stage Circuit Configuration
When termination resistance RT is connected between the two transmission lines, as shown in figure 7 the
current path situation is that current IOH on the side outputting a high level (in this case, the Y output)
flows to the side outputting a low level (in this case, the Z output) via RT, with the result that the low level
rise is large.
If termination resistance RT is dropped to GND on both transmit lines, as shown in figure 5 the current
path situation is that the current that flows into the side outputting a low level (in this case, the Z output) is
only the input bias current from the receiver. As this input bias current is small compared with the signal
current, it has almost no effect on the differential input signal at the receiver end.
Figure 6 shows the output voltage characteristics when termination resistance RT is varied.
Also, when used in a party line system, etc., the low level rises further due to the receiver input bias
current, so that it is probably advisable to drop the termination resistance to GND.
However, the fact that it is possible to make the value of RT equal to the characteristic impedance of the
transmission line offers the advantage of being able to hold the power dissipation on the side outputting a
high level to a lower level than in the above case.
Consequently, the appropriate use must be decided according to the actual operating conditions
(transmission line characteristics, transmission distance, whether a party line is used, etc.).
Figure 8 shows the output voltage characteristics when termination resistance RT is varied.
HD26LS31
10
5.0
4.0
3.0
2.0
1.0
0 –20 –40 –60 –80 –100
Output Current IOH (mA)
Output Voltage VOH (V)
V
CC
= 5.25 V
V
CC
= 4.75 V
VCC = 5.0 V Ta = 25°C
Figure 3 IOH vs. VOH Characteristics
0.5
0.4
0.3
0.2
0.1
0 1020304050
Output Current IOL (mA)
Output Voltage VOL (V)
VCC = 4.75 V
Ta = 25°C
VCC = 5.0 V
VCC = 5.25 V
Figure 4 IOL vs. VOL Characteristics
HD26LS31
11
Y
Z
"H"
"L"
IOH
RT
RT
IIN (Receiver)
RT = ZO
2
ZO is the transmission line characteristic
impedance
Figure 5 Example of Driver Use-1
5
2
1.0
0.5
0.2
0.1
0.0510 20 50 100 200 500 1 k 2 k 5 k 10 k 20 k 50 k
Termination Resistance RT (Ω)
Output Voltage VOH (Y), VOL (Z) (V)
VCC = 5 V
Ta = 25°C
Z
Y
"H" VOH
GND
RT
RT
VOL
VOH (Y)
VOL (Z)
Figure 6 Termination Resistance vs. Output Voltage Characteristics
Z
Y "H"
"L"
IOH
IOL
RT
IIN (Receiver)
RT = ZO
ZO is the transmission line characteristic
impedance
Figure 7 Example of Driver Use-2
HD26LS31
12
A feature of termination implemented as shown in figure 9 is that power dissipation is low when the duty of
the transmitted signal is high.
However, care is required, since if RT is sufficiently small, when the output on the pulled-up side goes low,
since the inverter transistor (Q 4 in figure 2) has no protection circuit, and so a large current will flow and
the output low level will rise.
Figure 10 shows the output voltage characteristics when termination resistance RT is varied.
With the method of using the driver described above, if termination resistance RT becomes sufficiently
small, the region within which the output current limiter circuit operates will be entered, as can be seen
from the I OH vs. VOH characteristics shown in figure 3. In this region, the output stage power dissipation is
large and the output voltage changes abruptly. A measure such as insertion of a capacitor in series with the
termination resistance is therefore necessary. Consequently, when selecting the transmission line, the
circuit termination resistance to be used requires careful consideration.
5
2
1.0
0.5
0.2
0.1
0.0510 20 50 100 200 500 1 k 2 k 5 k 10 k 20 k 50 k
Termination Resistance RT (Ω)
Output Voltage VOH (Y), VOL (Z) (V)
VOH (Y)
VOL (Z)
VCC = 5 V
Ta = 25°C
Z
"H" VOH
GND
RT
VOL
Y
Figure 8 Termination Resistance vs. Output Voltage Characteristics
VCC
RT
RT
Z
Y
Data input
Figure 9 Example of Driver Use-3
HD26LS31
13
5
2
1.0
0.5
0.2
0.1
0.0510 20 50 100 200 500 1 k 2 k 5 k 10 k 20 k 50 k
Termination Resistance RT (Ω)
Output Voltage VOH (Y), VOL (Z) (V)
VOL (Y)
VOH (Z) VCC = 5 V
Ta = 25°C
Z
"L" VOL
GND
RTVOH
YRT
VCC
Figure 10 Termination Resistance vs. Output Voltage Characteristic
HD26LS31
14
Package Dimensions
Hitachi Code
JEDEC
EIAJ
Mass
(reference value)
DP-16
Conforms
Conforms
1.07 g
Unit: mm
6.30
19.20
16 9
81 1.3
20.00 Max
7.40 Max
7.62
0.25
+ 0.13
– 0.05
2.54 ± 0.25 0.48 ± 0.10
0.51 Min
2.54 Min 5.06 Max
0° – 15°
1.11 Max
Hitachi Code
JEDEC
EIAJ
Mass
(reference value)
FP-16DA
—
Conforms
0.24 g
Unit: mm
*Dimension including the plating thickness
Base material dimension
*0.22 ± 0.05
*0.42 ± 0.08
0.12
0.15
M
2.20 Max 5.5
10.06
0.80 Max
16 9
18
10.5 Max
+ 0.20
– 0.30
7.80
0.70 ± 0.20
0° – 8°
0.10 ± 0.10
1.15
1.27
0.40 ± 0.06
0.20 ± 0.04
HD26LS31
15
Cautions
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4. Design your application so that the product is used within the ranges guaranteed by Hitachi particularly
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Tel: Tokyo (03) 3270-2111 Fax: (03) 3270-5109
Copyright Hitachi, Ltd., 2000. All rights reserved. Printed in Japan.
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