Texas Instruments SN75492


With the TMS0102 Texas Instruments introduced end of the year 1971 the first available standard calculator building block on a chip. The chip containes 3520-bit read-only program memory, a 182-bit random-access memory and a decimal arithmetic logic unit as well as control, timing, and output decoders but no drivers for the display. Most handheld calculators built around the TMS0100 make use of 7-segment LED displays. To simplify the interface and to reduce the component count,  Texas Instruments designed two special integrated circuits that allow direct interface between the TMS0100 and the TIL360, a multidigit display.

The circuits are designated SN75491 (segment driver) and SN75492 (digit driver). They meet the driving requirements of multiplexed, common-cathode displays and include the necessary pulldown resistors for the TMS0100 outputs.

The SN75492 digit driver includes six stages. Two SN75492 will be used for a calculator around the TMS0102.


TI-2500 and other early LED calculators

Technical Specification

Item Min Typ Max Unit Comments
VSS 6.6 7.2 9.0 V  
IL  250     mA VI=6.5 V, VO=3.5 V
IL     0.2 mA II=40 uA
VI-VD     1.2 V IL=250 mA
VI-VD     10 V SN75492A = 20 V


The SN75492 uses a standard DIP-14 package.

Pin Description

Pin IO Function Pin IO Function
1 O Digit output 1 14 I Digit input 1
2 O Digit output 2 13 O Digit output 6
3 I Digit input 2 12 I Digit input 6
4 V GND 11 V VSS
5 I Digit input 3 10 I Digit input 5
6 O Digit output 3 9 O Digit output 5
7 O Digit output 4 8 I Digit input 4


If you have additions to the above datasheet please email:

Joerg Woerner, February 02, 2001. No reprints without written permission.