??? 02/16/05 15:01 Read: times |
#87660 - LS, HCT and maybe AHCT Responding to: ???'s previous message |
Christian said:
Which i could use in a breadboard without suffering big problems like Kai said, i'm very concerned about this. SN74LS08, SN74HCT08 and maybe SN74AHCT08 should work. Of course, very much depends on your actual design, how you manage the ground routing, how much current is driven by the fast digital chips and how properly power supply decoupling is done. It cannot be guaranteed, that the one will work and the other not. But it should be clear, that the faster the chip is the more demanding the use of solid ground plane is. This solid ground plane provides not only lowest possible inductivity for the power supply decoupling measures, but also provides a low inductivity ground return path for the output signals of such a fast chip. With breadboard or wirewrap you add an enormous extra portion of inductivity to each line, which per se puts trouble into your design. But whether this actually results in a disaster or not depends on your actual circuit. One trick: If you have no solid ground plane for the ground return current of each decoupling capacitor, then connect two or three totally individual 10...100nF decoupling capacitors with shortest connections to the power supply pins of each chip. This will enormously decrease effective inductivity of power supply decoupling, because now three capacitors are connected in parallel. By this you can decrease noise across power supply pins by about a factor of two! This can directly be observed by the help of a good scope, by the way. Of course, you will not result in a performance that is better than using a solid ground plane... Kai |
Topic | Author | Date |
Problem getting 8051 chip to work | 01/01/70 00:00 | |
tie ~EA pin to Vcc | 01/01/70 00:00 | |
tie Vpp/~EA pin to Vcc | 01/01/70 00:00 | |
to connect or not? | 01/01/70 00:00 | |
conbnect | 01/01/70 00:00 | |
If it helps.... | 01/01/70 00:00 | |
Reset Capacitor | 01/01/70 00:00 | |
connect | 01/01/70 00:00 | |
T89C51RD2 | 01/01/70 00:00 | |
This device is ISP | 01/01/70 00:00 | |
VCC and GND? | 01/01/70 00:00 | |
I think you do not load | 01/01/70 00:00 | |
Series resistor for LED? | 01/01/70 00:00 | |
74F14 | 01/01/70 00:00 | |
give me +1 too | 01/01/70 00:00 | |
done | 01/01/70 00:00 | |
Sorry | 01/01/70 00:00 | |
LED Polarity | 01/01/70 00:00 | |
Does not seem to be the cause | 01/01/70 00:00 | |
Ouch! | 01/01/70 00:00 | |
FAST-TTL and breadboarded design | 01/01/70 00:00 | |
Ground bounce | 01/01/70 00:00 | |
Bad news 74F =( | 01/01/70 00:00 | |
HCT? | 01/01/70 00:00 | |
LS, HCT and maybe AHCT | 01/01/70 00:00 | |
Got it | 01/01/70 00:00 | |
wire wrap and breadboards | 01/01/70 00:00 | |
I use protoboard | 01/01/70 00:00 | |
the problem with that is | 01/01/70 00:00 | |
Thanks | 01/01/70 00:00 | |
Why do you want to use 74F chips? | 01/01/70 00:00 | |
well...![]() | 01/01/70 00:00 | |
maybe you are still in ISP mode? | 01/01/70 00:00 | |
1st things 1st please | 01/01/70 00:00 | |
Thanks | 01/01/70 00:00 | |
bounce on non PCB | 01/01/70 00:00 | |
Analytical thinking | 01/01/70 00:00 |