I found this useful information from TI.
But i still have doubt. May i know those 74HC573, 74HC245, 74HC02, 74HC32, 74HC138, and so on..Is CMOS or TTL IC? If those 74HCxx is CMOS IC then i will facing problem. Analyze as bellow:..
5.0V CMOS Voh=4.44V
3.3V LV Vih=2.0V
should not be any problem because Voh (CMOS) > Vih (LV), am I rite? In this case the 5V signal will harm the 3.3V device?
5.0V CMOS Vol=0.5V
3.3V LV Vil=0.8V
should not be any problem because Vol (CMOS) < Vil (LV), am I rite?
3.3V LVC Voh=2.4V
5V CMOS Vih=3.5V
problem because Voh (LV) < Vil (CMOS), am I rite?
3.3V LVC Vol=0.8V
5V CMOS Vil=1.5V
should not be any problem because Vol (LV) < Vil (CMOS), am I rite?
I very confusing after compare the TI information with 74HCxx datasheet. I did check the datasheet for 74HC245. The datasheet shown bellow:
74HC245 is CMOS device but the voltage level is not like TI information mention. This device voltage level most like TTL and LV category, am i rite?
One more doubt. Hope can get some advice.
All my board device are using 5V operation and almost all the logic gate IC is 74HCxxx. I have one LCD which is operate at 3.3V.
Can regulate the supply from 5Vcc to 3.3Vcc for all the 74HCxxx? make it standard voltage in the system. So that all the 74HCxxx Vil, Vih, Vol and Voh signal can be matching. I did check 74HC138, 74HC32, 74HC02 and so on... their min operation voltage is 2Vcc.
Some of the device i can't use 3.3V like example i have using 82C55 I/O expander, 4Vcc min operation, 62256 SRAM and so on... If the board able to drive 3.3V devices then 5V devices might not be drive-up. Any simple way or opinion can be advice?