To find the input/output voltages of different logic families (and decide wheter they
are compatible) is a quite fuzzy thing. The values vary from source to source and from
manufactorer to manufacturer. Here are some tables which should help you in some
cases. To get really reliable values, you have to take a look into the devicesīs datasheet
You should take the datasheet from the manufacturer you have (and not any)
if you want to know exact values.
Type | Specified | Compatibility | Input Current| Drive Curr | Supply | Speed
| Power Supply | Input | Output | L/H | L/H | Current |
-------+--------------+-----------+-----------+--------------+------------+---------+--------
CMOS | | | | | | |
-------+--------------+-----------+-----------+--------------+------------+---------+--------
AC | 3.3V/5V | CMOS | TTL, CMOS | -1uA/1uA | 24mA/-24mA | 80uA | 7.5ns
ACT | 5V | TTL, CMOS | TTL, CMOS | -1uA/1uA | 24mA/-24mA | 80uA | 10ns
VHC | 3.3V/5V | CMOS | TTL, CMOS | -1uA/1uA | 8mA/-8mA | 40uA | 8.5ns
VHCT | 5V | TTL, CMOS | TTL, CMOS | -1uA/1uA | 8mA/-8mA | 40uA | 9.5ns
HC | 2/4.5/6V | CMOS | TTL, CMOS | -1uA/1uA | 6mA/-6mA | 80uA | 25ns
HCT | 5V | TTL, CMOS | TTL, CMOS | -1uA/1uA | 6mA/-6mA | 80uA | 25ns
74C | 3-15V | CMOS | TTL, CMOS | -1uA/1uA | 12mA/-14mA | 300uA | 70ns
CD4K** | 3-15V | CMOS | TTL, CMOS | 10pA | 8mA/-1.25mA| 3uA | 40ns
-------+--------------+-----------+-----------+--------------+------------+---------+--------
BIPOLAR| | | | | | |
-------+--------------+-----------+-----------+--------------+------------+---------+--------
AS | 5V | TTL | TTL | -1mA/20uA | 64mA/-15mA | 90mA | 6.2ns
ALS | 5V | TTL | TTL | -0.1mA/20uA | 24mA/-15mA | 27mA | 10ns
LS | 5V | TTL | TTL | -200uA/20uA | 24mA/-15mA | 54mA | 18ns
S | 5V | TTL | TTL | -400uA/50uA | 64mA/-15mA | 120mA | 9ns
TTL* | 5V | TTL | TTL | -1.6mA/40uA | 40mA/-250mA| 41mA | 30ns
-------+--------------+-----------+-----------+--------------+------------+---------+--------
ECL | | | | | | |
-------+--------------+-----------+-----------+--------------+------------+---------+--------
300 | -5.7 to -4.2V| ECL | ECL | 0.5uA/240uA | -1.8V into | -65mA | 1.55ns
series| | | | | 50 Ohm | |
* 7407 used for specifications
** CD4010 used for specifications
Type | Specified | Compatibility | Drive Curr | Supply | Speed
| Power Supply | Input | Output | L/H | Current |
-------+--------------+-----------+-----------+------------+-------------+--------
CMOS | | | | | |
-------+--------------+-----------+-----------+------------+-------------+--------
AC | 3.3V | CMOS | CMOS | 12mA/-12mA | 20uA (3.3V) | 8.5ns
AC | 5V | CMOS | CMOS | 24mA/-24mA | 40uA (3.3V) | 6.5ns
ACT | 5V | TTL | CMOS | 24mA/-24mA | 40uA | 8ns
HC | 5V | CMOS | CMOS | 6mA/-6mA | 80uA | 21ns
HCT | 5V | TTL | CMOS | 6mA/-6mA | 80uA | 30ns
-------+--------------+-----------+-----------+------------+-------------+--------
BIPOLAR| | | | | |
-------+--------------+-----------+-----------+------------+-------------+--------
AS | 5V | TTL | TTL | 64mA/-15mA | 143mA | 7.5ns
ALS | 5V | TTL | TTL | 24mA/-15mA | 58mA | 10ns
LS | 5V | TTL | TTL | 24mA/-15mA | 95mA | 12ns
S | 5V | TTL | TTL | 64mA/-15mA | 180mA | 9ns
TTL | 5V | TTL | TTL | 16mA/-0.4mA| 22mA | 20ns
The CMOS outputs which have a high enough drive capability should also be able to
drive TTL inputs without serious problems.
Family | 74LS... | 74ALS... | 74HC... | 40...B | ACL...
---------------------+-------------+-------------+-------------+-------------+-------------
Supply Voltage min. | 4.75 | 4.75 | 2 | 3 | 2
[V] nom. | 5 | 5 | 5 | - | -
max. | 5.5 | 5.5 | 6 | 15 | 5.5
---------------------+-------------+-------------+-------------+-------------+-------------
Output current | | | | |
IOH/IOL [mA] | | | | |
standard | 16/16 | 8/8 | 4/4 | 1.6/1.6 | 24/24
high current | 48/48 | 24/48 | 6/6 | |
---------------------+-------------+-------------+-------------+-------------+-------------
Propagation time | | | | |
ns, pF load | 10/15 | 4/15 | 10/15 | 30/- | 3/-
---------------------+-------------+-------------+-------------+-------------+-------------
Input level | | | | |
min UIH [V] | 2 | 2 | 3.15 | 70% Ub* | 2 (@ Ub=5V)
max UIL [V] | 0.8 | 0.8 | 1.0 | 30% Ub** | 0.8
---------------------+-------------+-------------+-------------+-------------+-------------
Output level | | | | Ub=5V | (seemed to be reversed in the book, so i swapped them)
min UOH [V] | 2.7 | 2.7 | 4.9 | 4.95 | Ub-0.8
max UOL [V] | 0.4 | 0.5 | 0.1 | 0.05 | 0.5
---------------------+-------------+-------------+-------------+-------------+-------------
Input current | | | | |
max IIH [uA] | 20 | 20 | 1 | 1 | ?
max IIL [uA] | -400 | -100 | -1 | -1 | ?
---------------------+-------------+-------------+-------------+-------------+-------------
Ouput current | | | | |
max IOH [uA] | 400 | ? | 3.4 | 500 | ?
max IOL [uA] | -8000 | ? | -3400 | -500 | ?
* Buffered stages; higher for unbuffered
** Buffered stages; lower for unbuffered
| 40..B | 40..UB | 40..A | Unit
-------------------------+--------+--------+--------+------
Propagation time | 150 | 60 | 50 | ns
Max. interfering voltage | 30 | 20 | 30 | % of Vdd
Output impendance | 400 | 100-400| 100-400| Ohm
AC voltage gain | 68 | 23 | 23 | dB
Transition Frequency | 280 | 885 | 885 | KHz
Min. Slew-Rate of input | | | |
signal | 5 | 0.05 | 0.05 | mV/us
Suggested voltage range | 3...15 | 3...15 | 3...12 | V
Max. voltage range | 3...18 | 3...18 | 3...15 | V
| ...B, ...UB | ...A | Units
-------------------------+-------------+-------------+-------
| 5V | 15V | 5V | 10V |
-------------------------+------+------+------+------+-------
Min. "H" output volt. | 4.95 | 14.95| 4.95 | 9.95 | V
Max. "L" output volt. | 0.05 | 0.05 | 0.05 | 0.05 | V
Max. "H" output curr. | -0.12| -1 | -0.25| -0.25| mA
Max. "L" output curr. | 0.36 | 2.4 | 0.16 | 0.4 | mA
Min. "H" input voltage | 3.15 | 11 | 3.5 | 7.0 | V
Max. "L" input voltage | 1.5 | 4 | 1.5 | 3.0 | V
Min. input impendace | 15 | 15 | 15 | 15 | MOhm
Max. Quiescent current | 7.5 | 30 | 15 | 30 | uA
B .... Buffered
UB ... Unbeffered
A .... Standard
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Copyright (C) 2003 by Wiesner Thomas