[En-Nut-Discussion] lvttl and ttl

[Uwe Bonnes]

>>>>> "iVesWorking" == iVesWorking  <ivesworking at hotmail.com> writes:

    iVesWorking> my previous design is base on avr which run 5V TTL, but i
    iVesWorking> looking forward on 3.3V LVTTL Sam7X, but i not sure about
    iVesWorking> the need on adding a 3.3V to 5V bus convertor, or just
    iVesWorking> connect as usual, since device mention about their are 5V
    iVesWorking> tolerance, so i assume using the same connection without
    iVesWorking> the bus convertor will be fine. is this true?

The SAM is 5 Volt tolerant and can live with Signals coming from 5 V TTL or
5 V CMOS. 5 Volt TTL is also perfectly happy with 3.3 Volt CMOS Signals, as
coming from th SAM7. However 5 Volt CMOS will work (if supposed to work
together with 5 V TTL), or may work (if the VIH Voltage in the datasheet is
above 3.3 Volt). 5 Volt CMOS RAM will draw substantial more idel current
with 3.3 Volt CMOS input voltage, as the input buffers will be somehow cross
conducting.

So it depends...
-- 
Uwe Bonnes                bon at elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
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