Am 07.10.2002 17:26:55, schrieb "Ricardo H. Wiggers" <[email protected]>: >Thanks, but I still have a question.. In the case o MSP can I rely on the >internal protection diodes and simply add a resistor between buses (5V and >3V), provided my 5V chip accepts TTL levels (and MSP grants it)? With TI >2407 I know it´s possible, provided I keep the current low enough (and thats >not a problem with MOS...). Lets say a 10k res. between buses (in series). > >----- -------- > | | >MSP |----\/\/\-----| 5VCI > | | >----- --------
that works - somehow... i think the protection diodes can take up to 2mA so that's basicaly no problem to connect 5V peripherals through a 1K or bigger resistor. the problem is, that you inject current to VCC. this means it raises VCC if you don't drain the current somewhere. and that can become a problem, especialy as the MSP features low power modes ;-) so, if you drain the current, you inject over the protection diodes, you can do it. if you don't do it, the supply voltage of the MSP can get up to 5V, beyond the specs... (imagine the rest) chris
