| ??? 08/31/06 15:39 Read: times |
#123445 - What standard do you mean?? Responding to: ???'s previous message |
Oliver said:
The standard 78XX regs have a 10% tolerance, but they have largely been superceded by the 78XXA, which are 5%. I don't know what your standard is, but as Richard already mentioned, for me also the standard always was +-5%! Have a look at here: http://www.fairchildsemi.com/ds/LM/LM7805.pdf http://www.national.com/ds/LM/LM340.pdf#page=2 The "A"-types show less than +-5%. "10%" makes no sense, because lots of chips only tolerate a supply voltage tolerance of +-5% maximum. Oliver said:
f the circuitry can be proven to run correctly at the lower end of the supply voltage then you should probably use a reset chip with a lower threshold. I wouldn't do that! Even when the supply voltage tolerates a deviation of more than of 5%, you still may suffer from a change of speed and timing performance! The lower the supply voltage, the higher the propagation delay times! The better choice is to select a regulator showing a supply voltage of more than 5.0V. Selecting is a job lasting no more than a few seconds if you are prepared to do it. Kai |
