74LS & 74hc

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ZeleC

Joined: 18 Dec 2002
Posts: 296
Helped: 2

29 Jun 2003 12:38 74ls 74hc

hello
what is the difference between 74ls and 74hc
i know that the first is schottky and second cmos
what is the difference and where to use each kind ,and what is the advantage and disadvantge of each familly
any help? links,pdf,whatever...

gpenga

Joined: 19 Jun 2003
Posts: 11
Location: Brazil

29 Jun 2003 14:25 difference between74 hc, 74ls and 74c

hello
look the link
http://focus.ti.com/lit/misc/scyb004/scyb004.pdf
or
http://focus.ti.com/lit/misc/scyd013/scyd013.pdf
or
http://focus.ti.com/lit/misc/scyd013/scyd013.pdf
bye

WA

Joined: 27 Mar 2002
Posts: 74
Helped: 5
Location: wherever I go - there I am!

29 Jun 2003 22:47 difference between 74ls 74hc

ZeleC:

The main difference between the LS and HC is the logic of 74XX.

The 74LS is Transistor to Transistor logic. Uses Shottky transistors to reduce the stored charge and get higher switching speeds then with conventional bipolar transistors.

The 74HC uses MOSFET technology. Therefore can operate with wider variety of voltages. Power consumption better then TTL (but increases at higher frequencies). Has better noise margins so can work in noisy environments compared to TTL.

74HC are becoming more and more better replacements to older 74LS

Transition speeds are not too much different.
Prop delays for:
74LS - tpLH and tpHL about 15 nsec.
74HC - tpd about 18 nsec.

I don't know if this helps but, I hope this answers some questions.
WA

flatulent

Joined: 19 Jul 2002
Posts: 4877
Helped: 324
Location: Middle Earth

29 Jun 2003 23:11 74ls vs 74hc

The HC family was intended to exactly duplicate the speed of the LS but with lower power due to being CMOS.

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29 Jun 2003 23:11 Ads

bogdanm

Joined: 24 Jun 2003
Posts: 112
Helped: 1

30 Jun 2003 14:32 74 ac hc difference

There are a number of other interesting differences. For example, the HC circuits draw very little current at the inputs if you compare it with HC. At the same time, HC (Highspeed CMOS) also preserves other characteristics of the CMOS families, for example you can use 3.0V to power it (and even less, I don't have a datasheet here). Of course, if you to this, the maximum logical levels on the inputs change (with a 3V power suply you won't be able to tie 5V directly to an input, you need at least some minimal level adjustment). This is very interesting for people that design low-speed level shifters (5V-3.3V, seen for example in parallel port to JTAG adapters). Watch it, there is also HCT (Highspeed CMOS, TTL compatible) that makes the power range compatible with the LS series, so you can't power it from 3V. And then there are VHC, LVX, LVC, LVT and others, just to confuse you completely Smile

Zenner

Joined: 19 Sep 2001
Posts: 200

27 Jul 2003 18:09 74ls projects

The low power at low freq only. On the high speed, it req approximate as ttl LS series.

dipchip

Joined: 07 May 2001
Posts: 55

28 Aug 2003 16:20 difference between hc and vhc

One point that was implied, but maybe not stated. HC has the same functions as the corresponding TTL part, but the parameters are different. i.e. they are not interchangeable in a actual cicuit! The HCT line was introduced to be closer fit and can be interchanged in some cases.

D&S

Joined: 10 May 2004
Posts: 1

10 May 2004 10:55 74 family 74c 74hc 74ls

What's the diffirent between 74hc and 74ac (hc and ac)?

Zedman

Joined: 13 Oct 2003
Posts: 312
Helped: 2
Location: Hungary

10 May 2004 11:03 difference between 74ls and 74hc

Hope it helps Cool

:

Device Families:

TTL (74xx) True TTL
74L Low power
74S Schottky
74H High speed
74LS Low power - Schottky
74AS Advanced - Schottky
74ALS Advanced - Low power - Schottky
74F(AST) Fast - (Advanced - Schottky)
74C CMOS...................check Vcc levels
74HC (U) High speed - CMOS (Unbuffered output)
74HCT High speed - CMOS - TTL inputs
74AHC Advanced - High speed - CMOS
74AHCT Advanced - High speed - CMOS - TTL inputs
74FCT (-A) Fast - CMOS - TTL inputs (speed variations)
74FCT (-T, -AT) Fast - CMOS - TTL inputs (speed variations)
74AC Advanced - CMOS
74ACT Advanced - CMOS - TTL inputs
74FACT AC, ACT (Q) series
74ACQ Advanced - CMOS - Quiet outputs
74ACTQ Advanced - CMOS - TTL inputs - Quiet outputs

Bus Driver Families

74ABT Advanced - BiCMOS - Technology
74ABTE ABT - Enhanced Transceiver Logic
74ABTH Advanced - BiCMOS - Technology - bus Hold
74BCT BiCMOS - TTL inputs
74BTL Backplane - Transceiver - Logic
74GTL Gunning - Transceiver - Logic
74GTLP GTL Plus

Low Voltage Families

74ALB Advanced - Low Voltage - BiCMOS
74LV (U) Low - Voltage (Unbuffered output)
74LVC (R) (U) LV - CMOS (damping Resistor)(Unbuffered output)
74LVCH Low - Voltage - CMOS - bus Hold
74ALVC Advanced - Low - Voltage - CMOS
74LVT (R) (U) LV - TTL (damping Resistor(Unbuffered output)
74LVTZ Low - Voltage - TTL - High Impedance power-up
74ALVC (R) ALV - CMOS (bus Hold) (damping Resistor)
74ALVCH Advanced - Low - Voltage - CMOS - bus Hold
74LCX LV - CMOS (operates with 3v & 5v supplies)
74VCX LV - CMOS (operates with 1.8v & 3.6v supplies

4000 True CMOS (non-TTL levels)

Zed

bunalmis

Joined: 03 Jan 2003
Posts: 254
Helped: 5
Location: Turkey

10 May 2004 12:25 ttl hc hct ac ls comparison

If we compare the logic levels;

LSTTL, compatible with TTL
HCT, compatible with TTL
HC, not compatible with TTL

bogdanm

Joined: 24 Jun 2003
Posts: 112
Helped: 1

10 May 2004 13:03 difference between cmos 74hc and 74 hct series

HC - High-speed CMOS
AC - Advanced CMOS ( higher speeds that HC )
HCT - High-speed CMOS, TTL compatible (voltage levels compatible with TTL logic levels)
ACT - Advanced CMOS, TTL compatible (same)

If you need high speed (check the actual datasheets for numerical values) use ACT. Otherwise you can safely stick to HCT.