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4000 series

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The 4000 series is the general classification used to refer to the industry standard integrated circuits which implement a variety of logic functions using CMOS technology. They were introduced by RCA as CD4000 COS/MOS in 1968, as a lower power and more versatile alternative to the 7400 series of TTL logic chips.[Wright, Maury. Milestones That Mattered: CMOS pioneer developed a precursor to the processor EDN, 6/22/2006] Almost all IC manufacturers active during the era fabricated chips from this series.

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Initially, the 4000 series was slower than the popular 7400 TTL chips, but had the advantage of much lower power consumption, the ability to operate over a much wider range of supply voltages (3V to 15V), and simpler circuit design due to the vastly increased fanout. However their slower speed (initially only capable of about 1 MHz operation, compared with TTL's 10 MHz) meant that their applications were limited to static or slow speed designs. Later, new fabrication technology largely overcame the speed problems, while retaining backward compatibility with most circuit designs. Although all semiconductors can be damaged by electrostatic discharge, the high impedance of CMOS inputs made them more susceptible than bipolar, TTL, devices. Eventually, the advantages of CMOS (especially the later series such as 74HC) edged out the older TTL chips, but at the same time ever increasing LSI techniques edged out the modular chip approach to design. The 4000 series is still widely available, but perhaps less important than it was two decades ago.

The series was extended in the late 1970s and 1980s to include new types which implemented new or more greatly integrated functions, or were better versions of existing chips in the 4000 series. Most of these newer chips were given 45xx and 45xxx designations, but are usually still regarded by engineers as part of the 4000 series.

In the 1990s, some manufacturers (e.g. Texas Instruments) ported the 4000 series to their 74HC / 74HCT series to make chips like the 74HCT4060 that offers the functionality of a 4060 IC but with the speed of the 74HCT chip.

Contents

Design considerations

The original 4000 series was available in two versions. The A series was unbuffered, while the B series featured buffered outputs. The buffered outputs were able to source or sink more current than the unbuffered outputs, which could eliminate the need for discrete switching transistors in some designs. The buffered versions were also faster, as the signal rise time through the buffer was faster than the unbuffered chip's output transistorLancaster, Don. CMOS Cookbook, ISBN 0-672-21398-2

The 4000 series permits the use of "cookbook" design at least for slow design, where standard circuit elements can be created and shared, and connected to other circuits with few, if any, connection difficulties. This greatly speeds up the design of new hardware by reusing standard approaches to circuit design. In contrast, TTL circuits, while similarly modular, often required much more careful interfacing, since the limited fanout (and fan-in) meant that loading of each output had to be carefully considered. Some modern TTL families, like 74LS reduce this problem with fanouts of 20. It is also much easier to prototype LSI designs using the 4000 series and get repeatable and transferrable results when moving to the more integrated design.

Some care needed to be taken with the design of circuits using these chips. Many parts offered multiple gates in a single package. Using less than the complete number of gates was common, and an engineer who forgot to tie off the other gates would find the chip using too much current. The problem was caused by biasing in each gate. With the outputs disconnected, the gate would bias itself into a linear mode where the outputs were partially switched. This left the output buffer drawing a great deal of current, since it wasn't fully on or off.

Example common 4000 series chips

Notable parts

A few parts are notable in the 4000 series because of their level of integration compared to other . This list is intentionally incomplete and is meant to provide a sample of the more interesting parts in the series.

4017 decade counter

The 4017 IC is a 16-pin CMOS decade counter from the 4000 series. It takes clock pulses from the clock input, and makes the ten outputs come on in sequence every time a clock pulse arrives.

Pinout

4017 pinout

Pin number Name Purpose
1 6 The 6th sequential output
2 2 The 2th sequential output
3 1 The 1th sequential output
4 3 The 3th sequential output
5 7 The 7th sequential output
6 8 The 8th sequential output
7 4 The 4th sequential output
8 0V, VDD The connection to the 0V rail
9 9 The 9th sequential output
10 5 The 5th sequential output
11 10 The 10th sequential output
12 CO Carry out output - goes high when changing from 10 to 1
13 LE Latch enable - latches on the current output when high (i.e. the chip counts when LE is low)
14 CLK Clock in
15 RST Reset - sets output 0 high and outputs 1 through 9 low, when taken high
16 +9V, VCC The connection to the +VCC rail (voltage between +3V and +15V)

4026 counter and display decoder

The 4026 IC is a 16-pin CMOS seven-segment counter from the 4000 series. It counts clock pulses and returns the output in a form which can be displayed on a seven-segment display. This avoids using a binary-coded decimal to seven-segment decoder, but it can only be used to display the (decimal) digits 0-9.

4026 pinout

Pin number Name Purpose
1 CLK Clock in
2 CE Clock enable - when high, clock pulses increment the seven-segment
3 DE Display enable - the chip outputs to the seven-segment when this is high (i.e. when it's low, the seven-segment is off) - useful to conserve battery life, for instance
4 DEO Display enable out - for chaining 4026s
5 CO Carry out output - Is high when changing from 9 to 0
6 F Output for the seven-segment's F input
7 G Output for the seven-segment's G input
8 VDD The connection to the 0V rail
9 D Output for the seven-segment's D input
10 A Output for the seven-segment's A input
11 E Output for the seven-segment's E input
12 B Output for the seven-segment's B input
13 C Output for the seven-segment's C input
14 UCS Ungated C-segment - an output for the seven-segment's C input which isn't affected by the DE input
15 RST Reset - resets all outputs to low when taken high
16 VSS The connection to the +9V rail

4511 BCD to seven-segment decoder

The 4511 IC is a 16-pin CMOS BCD to seven-segment decoder from the 4000 series. It takes the binary-coded decimal from a binary counter and decodes it to drive a seven-segment display.

Pinout

4511 pinout

Pin number Name Purpose
1 2s Input for the 2s digit from the binary counter
2 4s Input for the 4s digit from the binary counter
3 LT Lamp test - when low, the chip takes all the segments on the display high (to test connections, etc.)
4 BI Blanking input - when low, the chip doesn't output to the display - to conserve battery life, for instance
5 LE Latch enable - latches on the current output when high (i.e. the inputs change the output when LE is low)
6 8s Input for the 8s digit from the binary counter
7 1s Input for the 1s digit from the binary counter
8 0V, VDD The connection to the 0V rail
9 E Output for the seven-segment's E input
10 D Output for the seven-segment's D input
11 C Output for the seven-segment's C input
12 B Output for the seven-segment's B input
13 A Output for the seven-segment's A input
14 G Output for the seven-segment's G input
15 F Output for the seven-segment's F input
16 +9V, VCC The connection to the +9V rail

References

External links

 

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