Logic family

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In digital technology, logic family refers to a series of components (usually as integrated circuits ) that provide elementary (such as logic gates ) and usually more complex logic circuits. The components of a family are manufactured using the same manufacturing process , use the same circuit technology, have similar electrical and mechanical properties and can therefore be combined without any problems.

The term logic family , in a broader sense, is often used to denote circuit technology. However, a mere match of the circuit technology used does not guarantee that two circuits have to be compatible .

nomenclature

74, 54, and 84 rows

Texas Instruments SN7400 in a 14-pin DIP package

The logic modules most frequently used today come from the so-called 74 series, the type number of which starts with 74 (see photo on the right). The following combination of numbers identifies the logic function of the circuit, which means that 00 in the example means that it is a NAND module. Later other logic families were developed, which differ in the manufacturing technique and the voltage levels used (and more, see below), but not in the logic function. In order to distinguish these families from the original one, letters are inserted between the 74 and the "function number". For example, an in has L ow-power S produced chottky technology NAND gate, the term 74LS00.

The manufacturer often puts two letters in front of the prefix, e.g. B. 'SN' for Texas Instruments or 'MC' for Motorola (now ON Semiconductor Corp ). ICs from different manufacturers can differ in further data (e.g. the maximum clock frequency), so they are not always easily interchangeable.

The date of manufacture can be derived from an additional number printed on the IC housing, in this case the 45th week of 1976.

All components in this series were originally delivered in DIP housings; SMD housings followed later (for example the SO design ), which are exclusively offered for modern successor series such as Low Voltage CMOS (LVCMOS, Series 74LVC ...).

The components of the 74 series are also available in versions for extended temperature ranges , which form the otherwise functionally identical 84 and 54 series.

prefix Temperature range designation
74 ' 0 ° C to +70 ° C commercially
84 ' −40 ° C to +85 ° C industrial
54 ' −55 ° C to +125 ° C military

4000 series

The 4000 series is a family of CMOS logic. It is rarely used today. Many commonly used building blocks, such as B. the PLL chip 4046 were also adopted in the 74 series. The name is then z. B. 74HC4046.

4500 series

The 4500 series is a continuation of the 4000 CMOS series. This is also available as a 74HC45xx CMOS variant.

Origin of the logic families

First logic families (RTL / DTL)

The first actual logic family was the resistor-transistor logic, mostly called RTL (for resistor transistor logic ). These integrated circuits consist exclusively of resistors and transistors ; the logic links are achieved by connecting the transistors in series or in parallel . RTL is a circuit technology; manufacturers have produced various proprietary component families.

With the diode-transistor logic (DTL) , the logic links are generated on the input side via diodes and then amplified and inverted with a transistor stage. DTL is also to be understood as circuit technology with incompatible series. The slow fail-safe logic ( LSL ) is a variant of DTL.

Today, RTL and DTL are only of historical interest.

Transistor-transistor logic (TTL)

The transistor-transistor logic (TTL) has replaced the diode networks at the inputs with transistors with several emitter connections. Although a number of semiconductor manufacturers initially produced their own logic families in TTL circuit technology, the TTL family from Texas Instruments soon established itself as the industry standard . The remaining manufacturers abandoned their proprietary lines and produced TTL circuits with the same specifications as Texas Instruments.

The numbering of Texas Instruments has also established itself: The first component in the series, consisting of four NAND gates with two inputs each, was called the SN7400, and the number was incremented for the following ones. Other manufacturers only replace the prefix SN with their own letter sequences, for example DM7400 from National Semiconductor . 7400 or '00 for short became the generic (manufacturer-independent) name for four NAND gates in TTL technology. ( See also: 74xx )

This TTL logic family was expanded very quickly by variants that were optimized for low power consumption or high switching speed and are called low-power TTL or high-speed TTL , with a conflict of objectives between speed and power consumption. The family designations L-TTL and H-TTL or also 74L and 74H resulted from the type numbers 74L00 and 74H00. The original 7400 logic family is often called standard TTL to distinguish it from the modified TTL families and from the umbrella term TTL (in the sense of TTL circuit technology). Using Schottky TTL (as the 74S series), low power consumption can be combined with higher speed; the low-power Schottky technology (as the 74LS series) was widely used. Further developments were later presented as Advanced Schottky (74AS series) and Advanced Low Power Schottky technology (74ALS series).

CMOS

Pin assignment for four NAND gates with two inputs each for TTL (7400) and CMOS (4011)

Logical circuits can be implemented not only with bipolar transistors , but also with field effect transistors (more precisely: MOSFETs ). The first circuit techniques with MOSFETs were called PMOS and NMOS and used exclusively p-channel MOSFET or n-channel MOSFET. PMOS or NMOS circuit technology was used for many digital circuits such as microprocessors , but no actual logic families emerged.

CMOS (for Complementary MOS ) is a further development of PMOS and NMOS and uses a complementary circuit, i.e. H. n- and p-channel MOSFETs are used in pairs, which is a prerequisite for the characteristic low quiescent current .

4000/4500 series

With the Series 4000, RCA Semiconductor developed the first logic family in CMOS technology, which - like the 7400 family in TTL technology - established itself as the industry standard and was produced by various manufacturers. Compared to TTL, this family is characterized by very low power consumption, a wide range for the supply voltage, but also slow switching processes and low-power output drivers. A major weakness of 4000 is the high sensitivity to electrostatic discharge (ESD, engl. Electro Static Discharge ), and the latch-up which can easily lead to the destruction of the circuit. With the 4000B logic family, this problem has been reduced by means of improved input protection circuits and further improvements to the electrical specifications have been introduced. The improved 4000B series is still produced and used today - albeit with a reduced range of types.

The 4000 family uses its own numbering and pin assignment, a quadruple NAND gate with two inputs each is called, for example, 4011 ('11) and not 7400 ('00 or 74H00, 74L00, 74LS00 etc.) as with the TTL modules . In addition to the deviating number, the pin assignment is also different: Although the ICs of both families are available in the same 14-pin DIP , the inputs and outputs are on different connections; in most cases the modules are not interchangeable. In the case of the exceptions with identical pin assignment, two type designations are sometimes printed: in addition to the number of the 4000 series, a 74C number ( see below ; for example six 4069 or 74C14 inverters ). There are also selected components in HC technology ; a component with a function and pin assignment, for example a 4017, is referred to as a 74HC4017.

After the 4000 series, further circuits in CMOS were developed. For example 4511B, a 7-seg decoder with memory, or 4518B / 4520B with two BCD / binary counters. Selected ICs are also available as 74HC45xx.

Series 74C… and 74HC…
The 74C logic family from National Semiconductor eliminates the disadvantage of the other pin assignment of the 4000 series: Although these components were constructed in CMOS technology, comparable to the 4000B, they used the numbering, function definitions and pin assignments of the 7400 series . The 74C family was not very important, but the subsequent CMOS families 74HC / HCT and 74AC / ACT did.

74HC… (high-speed CMOS) and 74HCT ... (high-speed CMOS with TTL-compatible inputs) use the numbering of the 74 logic modules. They are pin-compatible and functionally compatible. The 74HCT version is conditionally electrically compatible with 5 volt TTL circuits. The advantage over them is the lower input current and the lower supply current requirement. 74HC… and 74HCT… differ in the permissible tolerance of the operating voltage and the range of permitted and prohibited input levels. The components of the 74HCT series are compatible with their inputs with 5 V TTL and 3.3 V logic levels. 74HC… is characterized by the operating voltage range of 2 to 6 volts, for example when the voltage can drop during battery operation. The 74AC… (Advanced-high-speed) and 74ACT… (Advanced-high-speed with TTL-compatible inputs) series have been around since the 1980s. These series also have different pin assignments under the designations 74AC110… for an optimized low- inductive supply of the supply voltage. The 74LS… series has been replaced by the 74HCT… series.

More logic families

Other logic families are:

Manufacturer prefixes
prefix Manufacturer
AT THE AMD
HD Hitachi
MC Motorola
Pc Philips
M. STMicroelectronics
DM, MM, F National Semiconductor
⊔ Signetics
SN Texas Instruments
SP SPI
TC Toshiba
Overview of the most important logic families
family Type Manufacturer
prefix 		U B P V t pd Consumption
P V · t pd
Transistor-transistor logic (TTL)
Standard TTL 7400 ⊔, SN, MC, DM 5 V 10 m W 10 n s 100 p y
Low power Schottky TTL 74 LS 00 2 mW 10 ns 20 pJ
Schottky TTL 74 S 00 ⊔, SN, DM 19 mW 3 ns 57 pJ
Low-Power-Advanced-TTL 74 AS 00 SN, MC, DM 1 mW 4 ns 4 pJ
Fast TTL 74 F 00 ⊔, F, MC, SN 4 mW 3 ns 12 pJ
Advanced TTL 74 AS 00 SN 10 mW 1.5 ns 15 pJ
Emitter-coupled logic (ECL)
Standard ECL 10 100 ⊔, MC, F −5.2 V 35 mW 2 ns 60 pJ
10 200 MC 1.5 ns 50 pJ
High speed ECL 1600 70 mW 1 ns 70 pJ
10 H 100 35 mW 35 pJ
100 100 ⊔, F −4.5 V 50 mW 0.75 ns 38 pJ
10 E 100 MC −5.2 V 0.4 ns 20 pJ
100 E 100 −4.5 V 40 mW 16 pJ
Complementary metal-oxide-semiconductor (CMOS)
Standard CMOS 4000 TC 5 V
15 V 		0.3 mW MHz −1
3 mW MHz −1 		90 ns
30 ns 		30 pJ MHz −1
90 pJ MHz −1
4000 MC1
74 C 00 MM
High-speed CMOS 74 HC 00 MC, MM, SP,
SN, TC, PC 		2-6 V 0.5 mW MHz −1 ≈10 ns
(voltage
dependent) 		5 pJ MHz −1
74 HCT 00 5 V
Advanced CMOS 74 AC 00 SN, PC, F 2-6 V 0.8 mW MHz −1 ≈3 ns
(voltage
dependent) 		2 pJ MHz −1
74 ACT 00 SN, F 5 V
Low voltage CMOS 74 LV 00 SN, PC, MM, TC 3.3V

1-5 V

0.6 mW MHz −1 14 ns 8 pJ MHz −1
74 LVC 00 0.5 mW MHz −1 7 ns 4 pJ MHz −1
74 ALVC 00 0.4 mW MHz −1 4 ns 2 pJ MHz −1

Hints

  • Standard CMOS components work with U B from 3 to 18 V; Values ​​above are given for 5 and 15 V.
  • The 74HCT and 74ACT are TTL-compatible CMOS, so they can often replace the 74LS and 74ALS
  • 74HCT inputs (5 volt logic) can be controlled with outputs from 3.3 volt logic modules

See also

literature

  • TTL paperback . IWT Verlag, Vaterstetten, 1996 or newer
  • Pocket Guide . Texas Instruments, 1983 or newer

Web links