| ??? 03/16/10 17:45 Read: times |
#174212 - explanation Responding to: ???'s previous message |
Jason Khoo said:
1. 6mA Output Drive at 5V
2. Low Input Current of 1microA Max What does the number one mean? My understanding - The chip given 5V Vcc and it will give the output from the chip about 6mA... Is that right?? No -- this means that, assuming a 5V Vcc, each output can source or sink 6 mA. However, if you read a 74LS245 data sheet, you'll notice that it can sink 24 mA (when the output is low) and source 15 mA (when the output is high). (Also, its input current is 100 uA.) Maybe you're looking at a data sheet for the 74HC245, which has +/- 6mA output drive with input current of 1 uA. You must pay attention: the logic families (HC vs LS) are different! What does the number two mean?
My understanding - The chip only need about 1micro input and it will drive out the 6mA output. The 1uA spec means that the input will sink or source 1 uA (it's a high-impedance input). The output drive spec indicates that it can provide up to 6 mA -- but that is load-dependent. If the load is only one LS buffer then since that LS input only sinks/sources 100 uA then you can easily drive it and in fact several more in parallel. (Note that I've ignored dynamic current requirements.) -a |
| Topic | Author | Date |
| Wanna ask about SN74LS245 Octal Bus Transceivers | 01/01/70 00:00 | |
| backwards | 01/01/70 00:00 | |
| more specific | 01/01/70 00:00 | |
| The clue is in the name! | 01/01/70 00:00 | |
| More question | 01/01/70 00:00 | |
| Usually not needed... | 01/01/70 00:00 | |
| correction | 01/01/70 00:00 | |
| Correction?? | 01/01/70 00:00 | |
| Tell your lecturer ... | 01/01/70 00:00 | |
| First page of data sheet... | 01/01/70 00:00 | |
| What did he actually mean by that? | 01/01/70 00:00 | |
| In the spec i need explanation a bit | 01/01/70 00:00 | |
explanation | 01/01/70 00:00 | |
| '245 and '51 | 01/01/70 00:00 |