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LED Direct-Drive Calculator Circuits

Texas Instruments invented the Integrated Circuit (IC) in the year 1958. The first calculators with Integrated Circuits used DTL (Diode Transistor Logic), RTL (Resistor Transistor Logic) or TTL (Transistor Transistor Logic) elements. These ICs are small building blocks with typical 4 logic gates or 2 flip-flops in a 14 to 16 pin plastic housing. To get a working calculator you need more than 50 of them. The Cal-Tech project demonstrated in 1967 a calculator using only 3 LSI (Large Scale Integration) chips with more than 1,000 transistors per circuit and some additional shift registers. From this starting point, the calculator race created every year new Integrated Circuits with higher complexity following the Law of Moore. Working at another supplier of Integrated Circuits, the well known company Intel, Moore stated: Every three years the complexity of Integrated Circuits will double. The law is proved, within 30 years the complexity reached more than a million of transistors per chip.

Overview of LED Direct-Drive Calculator Chips

Manufacturer Type
Introduction		 VDD VLED Constant
(M-D-A-S)		 Special
Functions		 Program
Memory		 Data
Memory		 Keyboard
Scanning		 Clock
Circuitry		 Reset
Circuitry		 Segment
Current		 Fully
Integrated		 Process Die Size
Rockwell A5300
June 1974		 -15 V - 9V 2-2-2-2 6-Function Memory
[%]		 448 x 8 bits 48 x 4 bits Digit
KS Lines		 Internal
1 R		 External
1 R, 1 C
1 Diode		 External
8 R		 12 Discrete
DC/DC Conv.
Power Switch		 8 um
PMOS		 4.0 x 3.8 mm2
Texas Instruments TMS0950
March 1975		 -9 V - 9V 1-2-X-X 4-Function Memory
[+/−][%][√x]		 1,024 x 8 bits 64 x 4 bits Segment Internal
1 R, 1 C		 Internal External
3 R		 5 Discrete
Power Switch		 8 um
PMOS		 5.1 x 5.1 mm2

I. 

• A
• B
• C
• Z

 

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© Joerg Woerner, October 13, 2024. No reprints without written permission.