BI/RBO is wire-AND logic serving as blanking input (BI) and/or ripple-blanking output (RBO). The blanking out (BI) must be open or held at a HIGH
level when output functions 0 through 15 are desired, and ripple-blanking input (RBI) must be open or at a HIGH level if blanking or a decimal 0 is not
desired. X
=
input may be HIGH or LOW.
Note 3:
When a LOW level is applied to the blanking input (forced condition) all segment outputs go to a HIGH level regardless of the state of any other input
condition.
Note 4:
When ripple-blanking input (RBI) and inputs A0, A1, A2 and A3 are LOW level, with the lamp test input at HIGH level, all segment outputs go to a
HIGH level and the ripple-blanking output (RBO) goes to a LOW level (response condition).
Note 5:
When the blanking input/ripple-blanking output (BI/RBO) is OPEN or held at a HIGH level, and a LOW level is applied to lamp test input, all segment
outputs go to a LOW level.
Functional Description
The DM74LS47 decodes the input data in the pattern indi-
cated in the Truth Table and the segment identification
illustration. If the input data is decimal zero, a LOW signal
applied to the RBI blanks the display and causes a multi-
digit display. For example, by grounding the RBI of the
highest order decoder and connecting its BI/RBO to RBI of
the next lowest order decoder, etc., leading zeros will be
suppressed. Similarly, by grounding RBI of the lowest order
decoder and connecting its BI/RBO to RBI of the next high-
est order decoder, etc., trailing zeros will be suppressed.
Leading and trailing zeros can be suppressed simulta-
neously by using external gates, i.e.: by driving RBI of a
intermediate decoder from an OR gate whose inputs are
BI/RBO of the next highest and lowest order decoders. BI/
RBO also serves as an unconditional blanking input. The
internal NAND gate that generates the RBO signal has a
resistive pull-up, as opposed to a totem pole, and thus BI/
RBO can be forced LOW by external means, using wired-
collector logic. A LOW signal thus applied to BI/RBO turns
off all segment outputs. This blanking feature can be used
to control display intensity by varying the duty cycle of the
blanking signal. A LOW signal applied to LT turns on all
segment outputs, provided that BI/RBO is not forced LOW.
www.fairchildsemi.com
2
DM74LS47
Logic Diagram
Numerical Designations—Resultant Displays
3
www.fairchildsemi.com
DM74LS47
Absolute Maximum Ratings
(Note 6)
Supply Voltage
Input Voltage
Operating Free Air Temperature Range
Storage Temperature Range
7V
7V
0°C to
+70°C
−65°C
to
+150°C
Note 6:
The “Absolute Maximum Ratings” are those values beyond which
the safety of the device cannot be guaranteed. The device should not be
operated at these limits. The parametric values defined in the Electrical
Characteristics tables are not guaranteed at the absolute maximum ratings.
The “Recommended Operating Conditions” table will define the conditions
for actual device operation.
Recommended Operating Conditions
Symbol
V
CC
V
IH
V
IL
I
OH
I
OH
I
OL
T
A
Supply Voltage
HIGH Level Input Voltage
LOW Level Input Voltage
HIGH Level Output Current
a
−
g @ 15V
=
V
OH
(Note 7)
HIGH Level Output Current BI /RBO
LOW Level Output Current
Free Air Operating Temperature
0
Parameter
Min
4.75
2
0.8
−250
−50
24
70
Nom
5
Max
5.25
Units
V
V
V
µA
µA
mA
°C
Note 7:
OFF-State at a–g.
Electrical Characteristics
Over recommended operating free air temperature range (unless otherwise noted)
Symbol
V
I
V
OH
I
OFF
V
OL
Parameter
Input Clamp Voltage
HIGH Level
Output Voltage
Output HIGH Current Segment Outputs
LOW Level
Output Voltage
Conditions
V
CC
=
Min, I
I
= −18
mA
V
CC
=
Min, I
OH
=
Max,
V
IL
=
Max, BI /RBO
V
CC
=
5.5V, V
O
=
15V a
−
g
V
CC
=
Min, I
OL
=
Max,
V
IH
=
Min, a
−
g
I
OL
=
3.2 mA, BI /RBO
I
OL
=
12 mA, a –g
I
OL
=
1.6 mA, BI /RBO
I
I
I
IH
I
IL
I
OS
I
CC
Input Current @ Max
Input Voltage
HIGH Level Input Current
LOW Level Input Current
Short Circuit
Output Current
Supply Current
Note 8:
All typicals are at V
CC
=
5V, T
A
=
25°C.
Note 9:
Not more than one output should be shorted at a time, and the duration should not exceed one second.
Min
Typ
(Note 8)
Max
−1.5
Units
V
V
2.7
3.4
250
0.35
0.5
0.5
0.25
0.4
0.4
100
20
−0.4
µA
V
V
CC
=
Max, V
I
=
7V
V
CC
=
Max, V
I
=
10V
V
CC
=
Max, V
I
=
2.7V
V
CC
=
Max, V
I
=
0.4V
V
CC
=
Max (Note 9),
I
OS
at BI/RBO
V
CC
=
Max
−0.3
µA
µA
mA
mA
mA
−2.0
13
Switching Characteristics
at V
CC
= +
5.0V, T
A
= +25°C
R
L
=
665Ω
Symbol
Parameter
Conditions
Min
t
PLH
t
PHL
t
PLH
t
PHL
Propagation Delay
An to a –g
Propagation Delay
RBI to a –g (Note 10)
C
L
=
15 pF
Max
100
100
100
100
ns
ns
Units
Note 10:
LT
=
HIGH, A0–A3
=
LOW
www.fairchildsemi.com
4
DM74LS47
Physical Dimensions
inches (millimeters) unless otherwise noted
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
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