Difference between IC chip technologies

[skyglin]

There are different types of IC technology out there such as the LS series, HC series, the F series. I want to know the difference between them and how each type can most optimized for different applicatioins.
A compare and contrast between these technology would be really helpful. Thank you all.

skyglin

 

[serg1976]

difference between 74hc and 74hct

Hi,
try find datasheet sdyu001o.pdf in www.ti.com
It datasheet must help you. Unfortunately I don't attach this file.

serg1976

 

[rajesh13]

difference between a hc ic and a ls ic

There are different types of IC technology out there such as the LS series, HC series, the F series. I want to know the difference between them and how each type can most optimized for different applicatioins.
A compare and contrast between these technology would be really helpful. Thank you all.

skyglin

Do you want to know about the various tachnology like CMOS, ECL, TTL, IIL etc.

 

[skyglin]

different between chip or ic

I like to know the difference of IC chips that functions similarly, but are in different families. Such as 74LS14 and 74HC14, in what applications do we use the LS series, and what applications for HC series. And what are other families out there and how are they used?

skyglin

 

[cawan]

74hct244 examples

Different of technology will provides different of features that suit the specific application. For example, HC series provides normal TTL logic for combinational system design. However, AC or ACT technology is needed for optical communication driver design to provide larger current sinking instead of HC technology.

 

[delay]

74hct act hc ls

You need the following from TI and Motorola:

TI TTL

TTL Logic Data Book (74, 74S, 74LS)
ALS/AS Logic Data Book (74AS, 74ALS)
F Logic Data Book (74F)

TI CMOS
HC/HCT Logic Data Book (74HC, 74HCT)
AC/ACT Logic Data Book (74AC, 74ACT)
AHC/AHCT Logic Data Book (74AHC, 74AHCT)

Motorola
FAST and LSTTL Data (74F, 74LSTTL)
74 HC, 74HCT High Speed CMOS Data
FACT Data Book (74AC, 74ACT)
MECL Device Data (10K ECL)

 

[hcet]

difference between logic chips als act

jhon wakerly's book 'digital design and verification' explains the basic differences. use the search button in this forum. as far as i know, this part of the book exists as a pdf.
best regards.

 

[Big Boy]

hc ls ics difference

Of all of those families, there are mainly 2 major groups. All of those families are within either one of those 2 groups.

The major difference to know first is the TTL and CMOS technology.

TTL (LS, S, ALS, FS, no letters (as in 7407), ...) are made out of bi-polar transistor (NPN and PNP transistors). TTL stand for Transistor-Transistor-Logic.
- They take more current.
- Older technology, but still very commonly used.

CMOS (C, HC, AHC, HCT, ...) are made of MOS transistors. CMOS stand for Complementary Metal-Oxide-Silicon. MOS being a short therm for MOSFET (Metal-Oxide-Silicon Field-Effect Transistor). MOSFET is a newer technology (compared to bipolar transistors). The transistor is made so that you have a path between two of the pads (the source and drain), and the current between those pads are controled via a third pad (the gate). The major advantage is that the gate is actually electrically isolated from the source-drain path via a small layer of oxide-silicon (some sort of glass) so there's no electrical current from the gate to the other two pads. Normally, no current flow from the source to drain because the junction between the source and the inter-source-drain path work a little like a reverse-bias diode. By applying a voltage to the gate, this create an electrical field around the oxcide-silicon barrier, and in the source-drain path. This electrical field effect actually attract electrons from the source, and let current flow from source to drain (this is called a tunel efefct).

Well, this is a lot of theory, but the advantage of CMOS is:
- Much lower power requirement
- Much higher input impedence (since no current flow from the transistors gates to the source-drain channel).

Though, with those advantage, CMOS have one inherent weekness. For the field-effect to work properly inside a transistor, the insulator oxide-silicon layer have to be very very small. This meen that the maximum voltage that can be applied to the gate is very low (in the order of 30 Volts). 30V may seem greater than any applications may need, but you have to think about electro-static discharges (you know, when you tough a door knob and you get zapped...). A sinple zap like that is harmless for us, but is in the order of a few hundreds volts to a few thousand volts (very high voltage, very low current). But a simple electro-static discharge (ESD) on a CMOS gate is fatal for the transistor. Current will flow through the insulator layer, carbonizing (shorting) the gate to the path. In a TTL device, an ESD at input wouldn't usually cause problem, since there's electrical connection between the transistor base and emitter/collector. The current would just flow there, with too little current to cause problem.

So, with CMOS, you have to be carefull about ESD (wear ground straps, or at least, make sure you touch something that is grounded before touching CMOS devices, not wearing cloths that are static-loaded, ...).

Though, todays, many newer CMOS devices come with protections diodes at each inputs. This help a lot in redising ESD hazards, clamping the input voltage between GND-0.7V and Vcc+0.7V.


Now, for TTL, a quick overview of some of the families:
- <no markings> (ex: 7407) are the firsts TTL.
- S (ex: 74S07) use schottky diodes. Those are much faster than regular diodes, but take more power than the classic TTL.
- LS (ex: 74LS07) are the most popular TTL chips. They are low-power schottky. This is a compromize between the power-efficiency and speed efficiency.
There are some others too...

For CMOS
- C (ex: 74C07) are some of the first CMOS.
- HC (ex: 74HC07) are a higher-speed version, and are the most widely used today.
There are also some other versions...

Some chips use a 'LV' markings. Those are low-voltage chips (3.3V). Like the 'LVC'.

If we take the two groups, the input/output voltage range for each families are common within their groups (most TTL families are compatible within each others TTL families, and most CMOS are compatible beteen CMOS).

The problem occur when mixing CMOS and TTL.

A CMOS output can drive a *single* LS TTL without modifications. A single TTL input being due to the fact that TTL inputs take much more current than CMOS input. A CMOS output is designed mainly for CMOS input. The problem occur when a TTL output want to drive a CMOS input. CMOS input voltage range are much less tollerent than TTL output can give. TTL output a '1' as any voltage between 2.4V to Vcc. A CMOS input see a '1' need the input voltage to be around 3 to 4 volts to Vcc. So, a TTL could output 2.8V (still valid TTL '1') but a CMOS could be in a voltage range that is 'gray'. Weird things can happen (oscillation, see a zero, and worse, a much higher increase in power consumption).

A TTL can usually drive a CMOS by adding a pull-up resistor.

Lastly, since many technology today use TTL, the CMOS manufacturer start to look at the TTL to CMOS compatibility issue. So, many of them design CMOS devices that can accept TTL voltage levels at inputs. Those devices are called 'TTL compatible'. For example, the 'HCT' CMOS (ex: 74HCT244) is a CMOS device. It work as a regular HC, but accepting a TTL output at it's input without special adjustment. Though, the 'CMOS to a single TTL input' rule still remain. If you need to connect a CMOS to multiple TTL, then, use a single TTL buffer, and output of that buffer to other TTL.