Philips Semiconductors Linear Products
Product specification
LED decoder/driver
NE587
DESCRIPTION
The NE587 is a latch/decoder/driver for 7-segment common anode
LED displays. The NE587 has a programmable current output up to
50mA which is essentially independent of output voltage, power
supply voltage, and temperature. The data (BCD) inputs and LE
(latch enable) input are low-loading so that they are compatible with
any data bus system. The 7-segment decoding is implemented with
a ROM so that alternative fonts can be made available.
PIN CONFIGURATIONS
N Package
D
1
D
2
LE
BI/RBO
RBI
1
2
3
4
5
6
7
8
9
18
17
16
15
14
13
12
11
10
V
CC
f
g
a
b
c
d
e
POWER GND
FEATURES
•
Latched BCD inputs
•
Low loading bus-compatible inputs
•
Ripple-blanking on leading- and/or trailing-edge zeros
APPLICATIONS
D
3
D
0
I
P
DIG GND
D
1
Package
•
Digital panel motors
•
Measuring instruments
•
Test equipment
•
Digital clocks
•
Digital bus monitoring
D
1
D
2
LE
BI/RBO
RBI
1
2
3
4
5
20
19
18
17
16
15
14
13
12
11
V
CC
f
g
a
b
NC
c
d
e
POWER GND
NC 6
D
3
D
0
I
P
7
8
9
DIG GND 10
NOTE:
1. SOL and non-standard pinout.
ORDERING INFORMATION
DESCRIPTION
20-Pin Plastic Small Outline Large (SOL) Package
18-Pin Plastic Dual In-Line Package (DIP)
NOTES:
1. SOL and non-standard pinout
TEMPERATURE RANGE
0 to +70°C
0 to +70°C
ORDER CODE
NE587D
1
NE587N
DWG #
0172D
0407A
ABSOLUTE MAXIMUM RATINGS
T
A
=25°C unless otherwise specified.
SYMBOL
V
CC
V
IN
V
OUT
P
D
T
A
T
J
T
STG
T
SOLD
Supply voltage
Input voltage
(D
0
-D
3
, LE, RBI)
Output voltage
(a-g, RBO)
Power dissipation (25°C)
1
Ambient temperature range
Junction temperature
Storage temperature range
Soldering temperature (10sec max)
PARAMETER
RATING
-0.5 to +7
-0.5 to +15
-0.5 to +7
1000
0 to 70
150
-65 to +150
300
UNIT
V
V
V
mW
°C
°C
°C
°C
NOTES:
1. Derate power dissipation as indicated
N package—95°C/W above 55°C
August 31, 1994
530
853-1095 13721
Philips Semiconductors Linear Products
Product specification
LED decoder/driver
NE587
BLOCK DIAGRAM
BI/RBO (4)
V
CC
(18)
..
RBI (5)
D
0
D
1
D
2
D
3
(7)
(1)
(2)
(6)
DATA
LATCHES
BCD TO
7-SEGMENT
DECODER
LE
(3)
a (15)
b (14)
I
P
(8)
BANDGAP
REFERENCE
SEGMENT
CURRENT
DRIVER
c (13)
d (12)
e (11)
GND (9)
..
POWER GND (10)
f (17)
g (16)
August 31, 1994
531
Philips Semiconductors Linear Products
Product specification
LED decoder/driver
NE587
DC ELECTRICAL CHARACTERISTICS
V
CC
=4.75 to 5.25V, 0°C < T
A
< 70°C. Typical values are at V
CC
=5V, T
A
=25°C, R
P
=1kΩ (±1%), unless otherwise specified.
SYMBOL
V
CC
V
IH
V
IL
V
IC
PARAMETER
Operating supply voltage
Input high voltage
Input low voltage
Input clamp voltage
I
IN
=-12mA, T
A
=25°C
Inputs D
0
-D
3
, LE, RBI
V
IN
=2.4V
I
IH
Input high current
V
IN
=15V
Input BI (Pin 4)
RBI=H
V
IN
=V
CC
=5.25V
V
IN
=0.4V, Inputs D
0
-D
3
I
IL
Input low current
LE, RBI
Input BI
V
CC
=5.25V
RBI=H, V
IN
=0.4V
V
OL
Output low voltage
Output RBO
I
OUT
=3.0mA
Output RBO
V
OH
I
OUT
∆I
OUT
Output high voltage
Output segment
“ON” current
Output current ratio
(all outputs ON)
Output segment
I
OFF
I
CCO
“OFF” current
Supply current
I
OUT
=-50µA
RBI=H
Outputs “a” through “g”
V
OUT
=2.0V
With reference to “b” segment
V
OUT
=2.0V
Outputs “a” through “g”
V
OUT
=5.0V
V
CC
=5.25V
All outputs “ON”
V
OUT
>1V
V
CC
=5.25V
I
CCI
Supply current
All outputs blanked
50
70
mA
NOTES:
NE587 Programming:
The NE587 output current can be programmed, provided a program resistor, R
P
, be connected between I
P
(Pin 8) and Ground (Pin 9). The
voltage at I
P
(Pin 8) is constant (≈1.3V). Thus, a current through R
P
is I
P
≈
1.3V/R
P
, as shown in Figure 5. I
O
/I
P
is 20 in the 15 to 50mA output
current range.
33
55
mA
20
250
µA
0.90
1.00
1.10
20
25
30
mA
3.5
4.5
V
0.2
0.5
V
-0.7
mA
-5
-200
µA
1.0
15
10
10
15
100
µA
All inputs except BI
BI
TEST CONDITIONS
LIMITS
Min
4.75
2.0
2.0
Typ
5.00
Max
5.25
15
5.5
0.8
-1.5
V
V
µA
UNIT
V
V
August 31, 1994
532
Philips Semiconductors Linear Products
Product specification
LED decoder/driver
NE587
AC ELECTRICAL CHARACTERISTICS
V
CC
=5V, T
A
=25°C, R
L
=130Ω, C
L
=30pF including probe capacity.
SYMBOL
t
DAV
t
DAV
t
W
t
S
t
H
PARAMETER
Propagation delay (Figure 2)
Propagation delay (Figure 3)
Latch enable pulse width (Figure 4)
Latch enable setup time (Figure 4)
Latch enable hold time (Figure 4)
From data to LE
From LE to data
TEST CONDITIONS
From data to output
From LE to output
30
20
0
LIMITS
Min
Typ
135
135
Max
UNIT
ns
ns
ns
ns
ns
NOTES:
t
DAV
= (t
HL
+t
LH
)
TRUTH TABLE
BINARY
INPUT
-
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
**BI
INPUTS
LE
H
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
X
RBI
*
L
H
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
D
3
X
L
L
L
L
L
L
L
L
L
H
H
H
H
H
H
H
H
X
D
2
X
L
L
L
L
L
H
H
H
H
L
L
L
L
H
H
H
H
X
D
1
X
L
L
L
H
H
L
L
H
H
L
L
H
H
L
L
H
H
X
D
0
X
L
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
X
H
L
H
L
L
H
L
L
L
L
L
H
L
H
H
L
H
H
H
L
L
L
L
L
H
H
L
L
L
H
H
L
H
L
H
H
H
L
L
H
L
L
L
L
L
L
L
H
H
L
H
H
H
H
a
b
c
OUTPUTS
d
e
H
L
H
L
H
H
H
L
H
L
H
H
L
L
L
L
H
H
f
H
L
H
H
H
L
L
L
H
L
L
H
L
L
L
L
H
H
g
H
H
H
L
L
L
L
L
H
L
L
L
L
L
H
L
H
H
RBO
DISPLAY
STABLE
H
L
H
L
L
H
L
L
H
L
L
H
L
H
L
H
H
H
**
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
L**
STABLE
BLANK
0
1
2
3
4
5
6
7
8
9
-
E
H
L
P
Blank
Blank
NOTES:
H=HIGH voltage level, output is “OFF”
L=LOW voltage level, output is “ON”
X=Don’t care
* The RBI will blank the display only if a binary zero is stored in the latches.
** RBO/BI used as an input overrides all other input conditions.
NE587 PROGRAMMING
587 output current can be programmed by using a programming
resistor, RP, connected between RP (Pin 8) and GND (Pin 9). The
voltage at RP (Pin 8) is constant (
K =
1.3V). A partial schematic of
the voltage reference used in the NE587 is shown in Figure 1.
Output current to program current ratio, I
O
/I
P
, is 20 in the 15mA to
50mA range. Note that I
P
must be derived from a resistor (R
P
), and
not from a high-impedance source such as an I
OUT
DAC used to
control display brightness.
POWER DISSIPATION CONSIDERATIONS
LED displays are power-hungry devices, and inevitably, somewhat
inefficient in their use of the power supply necessary to drive them.
Duty cycle control does afford one way of improving display
efficiency, provided that the LEDs are not driven too far into
saturation; but the improvement is marginal. Operation at higher
peak currents has the added advantage of giving much better
matching of light output, both from segment-to-segment and
digit-to-digit.
August 31, 1994
533
Philips Semiconductors Linear Products
Product specification
LED decoder/driver
NE587
V
CC
I
O
1:20
I
P
+
V rP
RP
+
1.3V
RP
PIN 8
I
P
BAND GAP
REFERENCE
R
P
An output current of 10 to 50mA was chosen so that it would be
suitable for multiplexed operation of large-size LED digits. When
designing a display system, particular care must be taken to
minimize power dissipation within the IC display driver. Since the
output is a constant-current source, all the remaining supply voltage,
which is not dropped across the LED (and the digit driver, if used),
will appear across the output. Thus, the power dissipation will go up
sharply if the display power supply voltage rises. Clearly, then, it is
good design practice to keep the display supply voltage as low as
possible, consistent with proper operation of the supply output
current sources. Inserting a resistor or diode in series with the
display supply is a good way of reducing the power dissipation
within the integrated circuit segment driver, although, of course, total
system power remains the same.
Power dissipation may be calculated as follows. Referring to Figure
6, the two system power supplies are V
CC
and V
S
. In many cases,
these will be the same voltage. Necessary parameters are:
V
CC
V
S
I
CC
I
SEG
V
F
K
DC
Supply voltage to driver
Supply voltage to display
Quiescent supply current of driver
LED segment current
LED segment forward voltage at I
SEG
% Duty cycle
Figure 1.
TIMING DIAGRAMS
D
0
–D
3
t
PLH
OUTPUT
t
PHL
LE = L
V
F
, the forward LED drop, depends upon the type of LED material
(hence the color) and the forward current. The actual forward
voltage drops should be obtained from the LED display
manufacturer’s literature for the peak segment current selected;
however, approximate voltages at nominal rated currents are:
Red
Orange
Yellow
Green
LE
Figure 2. t
P
Data to Output
LE
t
PLH
t
PHL
1.6 to 2.0V
2.0 to 2.5V
2.2 to 3.5V
2.5 to 3.5V
t
W
D
0
–D
3
D
0
–D
3
OUTPUT
OUTPUT
Figure 3. t
P
Latch Enable to Output
a
f
g
b
e
d
c
Segment Identification
August 31, 1994
534
ÉÉÉ
ÉÉÉ
ÉÉÉ
ÉÉÉÉÉÉ ÉÉÉÉÉÉÉÉ
ÉÉ
ÉÉÉÉÉÉ ÉÉÉÉÉÉÉ
ÉÉÉÉÉÉ ÉÉÉÉÉÉÉ
ÉÉÉÉÉÉ ÉÉÉÉÉÉÉ
t
S
t
H
Figure 4. Setup and Hold Times
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