| ??? 01/25/05 13:54 Read: times |
#85754 - No latch-up Responding to: ???'s previous message |
Annibal said:
Could it cause a latch up condition ? No. Latch-up can only occur if the potential at input is higher than supply voltage. But if Vcc is 5V, means if LM324 and micro get the same supply voltage, then I see no reason that latch-up could occur. From your schematic it's not clear how you manage lines L1...4, C1..4. But I hope you do never pull-down L2? Otherwise a short circuit current of more than 40mA could flow into the micro! This could damage the micro, or at least cause heavy trouble. Connect a voltmeter across 330Ohm resistor. From datasheet of LM324 a potential of 3.5V should be provided even with this rather low load impedance. So, micro should see about 3.5V - 0.7V = 2.8V, which should be enough for the micro to detect logical high state. Could you give some more details, how you scan the keyboard? What is pulled-down or high, are diodes used, etc. Kai |
| Topic | Author | Date |
| P89C51RD2 x P89V51RD2 | 01/01/70 00:00 | |
| dead link | 01/01/70 00:00 | |
| differences | 01/01/70 00:00 | |
| P89C51RD2 x P89V51RD2 | 01/01/70 00:00 | |
| Latch UP condition ? | 01/01/70 00:00 | |
| Why this way? | 01/01/70 00:00 | |
| where is | 01/01/70 00:00 | |
| No latch-up | 01/01/70 00:00 | |
The other way round | 01/01/70 00:00 |