Fairchild Semiconductor DM7447AN, DM7446AN Datasheet

DM7446A, DM7447A
BCD to 7-Segment Decoders/Drivers

DM7446A, DM7447A BCD to 7-Segment Decoders/Drivers

September 1986
Revised February 2000

General Description

The DM7446A and DM74 47A feature active- LOW outputs
designed for driving common- ano de LEDs or inc and esce nt
indicators directly. All of the circuits have full ripple-blank­ing input/output controls and a lamp test input. Segment
identification and resu ltant di splays a re shown on a fo llow­ing page. Display patterns for BCD input counts above nine
are unique symbols to authenticate input conditions.

All of the circuits incorporate automatic leading and/or trail­ing-edge, zero-blankin g control (RBI and RBO). Lam p test
(LT) of these devices may be performed at any time when
the BI/RBO node is at a HIGH logic level. All typ es cont ain
an overriding blanking input (BI) which can be used to con­trol the lamp intensity (by pulsing) or to inhibit the outputs.

Features

■ All circuit types featur e lamp inte nsity modulati on capa­bility

■ Open-collector outputs drive indicators directly

■ Lamp-test provision

■ Leading/trailing zero suppression

Ordering Code:

Order Number Package Number Package Description

DM7446AN N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
DM7446AN N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide

Connection Diagram

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Function Table

Decimal or Inputs BI/RBO Outputs

Function LT RBI D C B A (Note 1) a b c d e f g

0 HHLLLL H LLLLLLH
1 HXLLLH H HLLHHHH
2 HXLLHL H LLHLLHL
3 HXLLHH H LLLLHHL

DM7446A, DM7447A

4 HXLHLL H HLLHHLL
5 HXLHLH H LHLLHLL
6 HXLHHL H HHLLLLL
7 HXLHHH H L LLHHHH(Note 2)
8 HXHLLL H LLLLLLL

9 HXHLLH H LLLHHLL
10 HXHLHL H HHHLLHL
11 HXHLHH H HHLL HHL
12 HXHHL L H HLHHHL L
13 HXHHLH H LHHLHLL
14 HXHHHL H HHHLLLL
15 HXHHHH H HHHHHHH
BI XXXXXX L HHHHHHH(Note 3)

RBI HLL LLL L HHHHHHH(Note 4)

LT LXXXXX H LLLLLLL(Note 5)

H = HIGH level, L = LOW level, X = Don’t Care

Note 1: BI/RBO is a wire-AND logic servin g as blanking input (BI) and / or ripple-blanking outp ut ( R BO).
Note 2: The blanking input (BI) must be OPEN o r held at a HIGH logic le v el w hen output functions 0 t hrough 15 are desir ed. The ripple-blanking input (RBI)

must be OPEN or HI GH if blanking of a decimal ze ro is not desired.

Note 3: When a LOW logic level is applied dire c t ly to the blanking input (BI), all segment outputs are HIGH regardless of the level of any other input.
Note 4: When ripple-blanking input (RBI) and inputs A, B, C , and D are at a LOW level with the lamp test input HI GH , all segment outputs go H and the rip-

ple-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 HIGH and a LOW is applied to the lamp-test input, all segment outputs are

L.

Note

Logic Diagram

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