I'm trying to identify an SMD on a PC board with some SPST keypad switches. It has 4 terminals and is marked M1I. Each is labeled DA1, DA2, etc. on the silkscreen, and two of the four terminals are marked A and K. All four terminals connect off in different destinations. I'm guessing this is some sort of debouncer or logic-level-shifter? But I'd like to know, if anyone has any suggestions.
On Thu, 09 Oct 2008 19:37:48 -0500, Richard J Kinch put finger to keyboard and composed:
Diode array? (A)node/(K)athode?
- Franc Zabkar
-- Please remove one \'i\' from my address when replying by email.
On Fri, 10 Oct 2008 13:28:46 +1100, Franc Zabkar put finger to keyboard and composed:
Maybe the DAx parts are wired as follows:
IN1 >----+-----> to uP | o |
+Vcc |--|
Yes, good call, thank you. Each chip is two diodes, four leads total. It explains all the resistance measurements being open circuit, as the ohmmeter wasn't overcoming the forward voltage drop. Measuring with a diode tester succeeds.
I think the diodes are either encoding matrix signaling, or perhaps the pull up/down you mention.
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