Philips Semiconductors Linear Products

Product specification

NE587

LED decoder/driver

August 31, 1994

533

AC ELECTRICAL CHARACTERISTICS

SYMBOL

PARAMETER

TEST CONDITIONS

LIMITS

UNIT

SYMBOL

PARAMETER

TEST CONDITIONS

Min

Typ

Max

UNIT

Propagation delay (Figure 2)

From data to output

135

ns

Propagation delay (Figure 3)

From LE to output

135

ns

Latch enable pulse width (Figure 4)

30

ns

Latch enable setup time (Figure 4)

From data to LE

20

ns

Latch enable hold time (Figure 4)

From LE to data

0

ns

NOTES:

TRUTH TABLE

BINARY

INPUT

INPUTS

OUTPUTS

DISPLAY

BINARY

INPUT

LE

RBI

a

b

c

d

e

f

g

RBO

DISPLAY

-

H

*

X

X

X

X

STABLE

**

STABLE

0

L

L

L

L

L

L

H

H

H

H

H

H

H

L

BLANK

0

L

H

L

L

L

L

L

L

L

L

L

L

H

H

0

1

L

X

L

L

L

H

H

L

L

H

H

H

H

H

1

2

L

X

L

L

H

L

L

L

H

L

L

H

L

H

2

3

L

X

L

L

H

H

L

L

L

L

H

H

L

H

3

4

L

X

L

H

L

L

H

L

L

H

H

L

L

H

4

5

L

X

L

H

L

H

L

H

L

L

H

L

L

H

5

6

L

X

L

H

H

L

L

H

L

L

L

L

L

H

6

7

L

X

L

H

H

H

L

L

L

H

H

H

H

H

7

8

L

X

H

L

L

L

L

L

L

L

L

L

L

H

8

9

L

X

H

L

L

H

L

L

L

L

H

L

L

H

9

10

L

X

H

L

H

L

H

H

H

H

H

H

L

H

-

11

L

X

H

L

H

H

L

H

H

L

L

L

L

H

E

12

L

X

H

H

L

L

H

L

L

H

L

L

L

H

H

13

L

X

H

H

L

H

H

H

H

L

L

L

H

H

L

14

L

X

H

H

H

L

L

L

H

H

L

L

L

H

P

15

L

X

H

H

H

H

H

H

H

H

H

H

H

H

Blank

**BI

X

X

X

X

X

X

H

H

H

H

H

H

H

L**

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

the voltage reference used in the NE587 is shown in Figure 1.

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.