7400 Logic Series Technologies Summary
Understand the differences between the different families of technologies used within the different types of 7400 series logic families: 74xx, 74LS, 74LV, etc
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Logic IC families & Technologies Includes:
IC logic families & technolgies summary chart
Numbering schemes
7400 Series TTL
7400 sub-families listing
The 7400 series of logic chips has been particularly successful since it was first launched in 1966.
Although the original chips are now dated, they can still be used, but the main way in which these chips have left their legacy is that new sub-families or technologes have been developed which meet the needs of today's logic chip requirements.
There are sub-families or technologies that support the low voltage requirements of many of today's designs, as well as providing fast operating times, etc.
To give a good idea of what the different sub-families or technologies provide, I've assembled some tables providing the basic information.
Bipolar Series of 7400 Logic |
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Family | Name | Supply (V) | tpd (ns) | IOL (mA) | IOH (mA) | Details |
74 | Standard TTL | 5 ± 5% | 22 | 16 | -0.4 | Original TTL introduced in 1966. |
74H | High speed | 5 ± 5% | 10 | 20 | -0.5 | Higher speed, but higher dissipation compared to standard TTL. |
74L | Low power | 5 ± 5% | 60 | 3.6 | -0.2 | Lower power, lower performance. |
74S | Schottky | 5 ± 5% | 5 | 20 | -1 | Used Schottky diode to reduce delays. |
74LS | Low power Schottky | 5 ± 5% | 15 | 8 | -0.4 | Same technology as 74S but with lower power and slightly slower performance. |
74F | Fast | 5 ± 5% | 3.9 | 20 | -1 | This was originally the Fairchild version of the 74AS family. |
74AS | Advanced Schottky | 5 ± 10% | 4.5 | 20 | -2 | |
74ALS | Advanced Schottky | 5 ± 10% | 4.5 | 20 | -2 |
The Bipolar series of the 7400 logic chips started off this popular and standard series, but as technology advanced and lower power requirements came to the fore, CMOS technology was utilised for new sub-families within the overal series.
BCMOS & BiCMOS Series of 7400 Logic |
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Family | Name | Supply (V) | tpd (ns) | IOL (mA) | IOH (mA) | Details |
74C | CMOS | 3.0 - 15 | 60 | 0.36 | -0.36 | Similar to the buffered 4000 series and levels not compatible with standard TTL. |
74HC | High speed CMOS | 2.0 - 6.0 | 15 | 4 | -4 | Performance similar to 74LS and with CMOS logic levels. |
74HCT | High speed CMOS | 5 ± 10% | 15 | 8 | -4 | Similar performance to 74LS and with TTL logic levels. |
74AHC | Advanced high speed CMOS | 2.0 - 5.5 | 5.5 | 8 | -8 | Up to three times as fast as 74HCT and utilises TTL logic levels. |
74AC | Advanced CMOS | 2.0 - 6.0 | 8 | 24 | -24 | CMOS logic levels. |
74ACT | Advanced CMOS | 5.0 ± 10% | 8 | 24 | -24 | TTL logic levels. |
As the operating voltages for microprocessor have fallen to reduce power consumption and increase the levels of integration, so too the operating voltages for some new sub-families have followed suit.
In order to be able to interface with them and run from the same supplies, new sub-families have been created.
Low Voltage CMOS Series of 7400 Logic |
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---|---|---|---|---|---|---|
Family | Name | Supply (V) | tpd (ns) | IOL (mA) | IOH (mA) | Details |
74LVT | Low voltage BiCMOS | 2.7 - 3.6 | 4.1 | 32 | -20 | TTL logic levels with 5V tolerant inputs and outputs. |
74LV | Low voltage CMOS | 2.7 - 3.6 | 18 | 6 | -6 | TTL logic levels. |
74LVC | Low voltage CMOS | 2.0 - 3.6 | 6 | 24 | -24 | TTL logic levels. |
74ALVC | Advanced low voltage CMOS | 1.65 - 3.6 | 3 | 24 | -24 | 3.3V tolerant inputs and output.s |
74LVX | Low voltage high-speedCMOS | 2.0 - 3.6 | 9.7 | 4 | -4 | TTL logic levels, 5V tolerant inputs, and faster than other types at low voltages. |
74AUC | Advanced ultra-low voltage CMOS | 0.8 - 2.7 | 2 | 9 | -9 | Very low voltage logic chips with 3.3V tolerant inputs. |
These represent some of the more widely used 74 series logic sub-families. The basic concept has been continued since the first chips were released in the mid 1960s, and although it is rare to see PCBs full of these chips, they are still used as logic surrounding microprocessors, microcontrollers and the like.
Written by Ian Poole .
Experienced electronics engineer and author.
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