5-56

FAST AND LS TTL DATA

BCD TO 7-SEGMENT

DECODER/DRIVER

The SN54 / 74LS47 are Low Power Schottky BCD to 7-Segment Decod-

er / Drivers consisting of NAND gates, input buffers and seven AND-OR-IN-

VERT gates. They offer active LOW, high sink current outputs for driving

indicators directly. Seven NAND gates and one driver are connected in pairs

to make BCD data and its complement available to the seven decoding

AND-OR-INVERT gates. The remaining NAND gate and three input buffers

provide lamp test, blanking input / ripple-blanking output and ripple-blanking

input.

The circuits accept 4-bit binary-coded-decimal (BCD) and, depending on

the state of the auxiliary inputs, decodes this data to drive a 7-segment display

indicator. The relative positive-logic output levels, as well as conditions

required at the auxiliary inputs, are shown in the truth tables. Output

configurations of the SN54 / 74LS47 are designed to withstand the relatively

high voltages required for 7-segment indicators.

These outputs will withstand 15 V with a maximum reverse current of

250

µA. Indicator segments requiring up to 24 mA of current may be driven

directly from the SN74LS47 high performance output transistors. Display

patterns for BCD input counts above nine are unique symbols to authenticate

input conditions.

The SN54 / 74LS47 incorporates automatic leading and / or trailing-edge

zero-blanking control (RBI and RBO). Lamp test (LT) may be performed at any

time which the BI / RBO node is a HIGH level. This device also contains an

overriding blanking input (BI) which can be used to control the lamp intensity

by varying the frequency and duty cycle of the BI input signal or to inhibit the

outputs.

14

13

12

11

10

9

1

2

3

4

5

6

VCC

7

16

15

8

f

g

a

b

c

d

e

B

C

LT BI / RBO RBI

D

A

GND

CONNECTION DIAGRAM DIP (TOP VIEW)

PIN NAMES

LOADING (Note a)

HIGH

LOW

A, B, C, D

RBI

LT

BI / RBO

a, to g

BCD Inputs

Ripple-Blanking Input

Lamp-Test Input

Blanking Input or

Ripple-Blanking Output

Outputs

0.5 U.L.

0.5 U.L.

0.5 U.L.

0.5 U.L.

1.2 U.L.

Open-Collector

0.25 U.L.

0.25 U.L.

0.25 U.L.

0.75 U.L.

2.0 U.L.

15 (7.5) U.L.

NOTES:

a) 1 Unit Load (U.L.) = 40

µA HIGH, 1.6 mA LOW.

b) Output current measured at VOUT = 0.5 V

The Output LOW drive factor is 7.5 U.L. for Military (54) and 15 U.L. for Commercial (74) Temperature Ranges.

SN54/74LS47

BCD TO 7-SEGMENT

DECODER/ DRIVER

LOW POWER SCHOTTKY

J SUFFIX

CERAMIC

CASE 620-09

N SUFFIX

PLASTIC

CASE 648-08

16

1

16

1

ORDERING INFORMATION

SN54LSXXJ

Ceramic

SN74LSXXN

Plastic

SN74LSXXD

SOIC

16

1

D SUFFIX

SOIC

CASE 751B-03

LOGIC SYMBOL

VCC = PIN 16

GND = PIN 8

7 1

2

6 3

5

13 12 11 10 9 15 14 4

A B C D LT RBI

a

b

c

d

e

f

g

BI/

RBO