Page 145 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

Input Lines Output Lines
Digits Display
Pattern
A B C D a b c d e f g

0 0 0 0 0 1 1 1 1 1 1 0 0
1 0 0 0 1 0 1 1 0 0 0 0 1

2 0 0 1 0 1 1 0 1 1 0 1 2

3 0 0 1 1 1 1 1 1 0 0 1 3
4 0 1 0 0 0 1 1 0 0 1 1 4

5 0 1 0 1 1 0 1 1 0 1 1 5

6 0 1 1 0 1 0 1 1 1 1 1 6

7 0 1 1 1 1 1 1 0 0 0 0 7

8 1 0 0 0 1 1 1 1 1 1 1 8

9 1 0 0 1 1 1 1 1 0 1 1 9
The 4543B BCD to 7 segment latch/decoder/driver is designed for liquid crystal displays. Pins A, B, C, D represent
BCD inputs with A as a Least Significant Bit (LSB)Significant Bit (MSB). Pins a to g are the seven segment outputs.
The IC 4543B has three control terminals LD (Latch Disable), PH (Phase) and BL (Blank). In normal use, the LD
terminal is held high, and the BL. terminal is tied low. The state of the PH terminal depends on the type of display
that is being drive. For driving LCD displays, a square wave. About 60 Hz swinging fully between the GND and
Voce values must be applied to the phase terminal.

The display can be blanked by simply driving the BL terminal to the logic high state. When the LD terminal is in
its normal high state, BCD inputs are decoded and fed directly to the seven segment output terminals of the IC.
When the LD terminal is pulled low, the BCD input signals that are present at the moment of transition are latched
into memory and fed to the seven segment outputs.
Applications of Decoder Driver ICs:
The following are some important applications of decoder driver ICs −

Decoder driver ICs are used in computers for addressing memory locations.
Decoder driver ICs are also used for code conversion such as BCD to 7-segment, binary to decimal, etc.
Decoder driver ICs are also used in de-multiplexing of digital signals.
IC L7106 and IC L7107
The Maxim IC L7106 and IC L7107 are monolithic analog-to-digital converters. They have very high input
impedances and require no external display drive circuitry. On-board active components include polarity and
digit drivers, segment decoders, voltage reference and a clock circuit. The IC L7106 will directly drive a non-
multiplexed Liquid crystal display (LCD), whereas the IC L7107 will directly drive a common anode light emitting
diode display.

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CITS : E & H - Electronics Mechanic - Lesson 77 - 83