I'm trying to interface my electronics with an existing remote. The remote requires me to set one of its pins to either low or nothing (not connected) to activate it.

While getting the "low" value is easy, I have more doubts about the "nothing". It currently works if I use the "high impedance" state of a CD74HC125E chip. But as the remote consumes about 1.5 micro amp, I'm worried that the "high impedance" state might be a little too low sometimes.

I tried reading the datasheet, but I'm still a newbie and I can't figure out where to read this impedance. Any help?

Datasheet: http://pdf1.alldatasheet.com/datasheet-pdf/view/27003/TI/CD74HC125/+Q51QWUPGZwEYtKhBYw+/datasheet.pdf

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    \$\begingroup\$ Have you considered an open-drain buffer instead? \$\endgroup\$ May 26 '13 at 8:59
  • \$\begingroup\$ datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/… \$\endgroup\$
    – jippie
    May 26 '13 at 9:06
  • \$\begingroup\$ @Vazquez Definitely not, didn't know about it. What is it / would it be a better solution? \$\endgroup\$ May 26 '13 at 9:06
  • \$\begingroup\$ en.wikipedia.org/wiki/Open_collector \$\endgroup\$
    – jippie
    May 26 '13 at 9:07
  • \$\begingroup\$ Looks like a nice solution. However the end goal is to use an arduino to control the remote. The pins of an arduino can be set to high impedance as well. Would it be viable, or is the open drain still a better solution? \$\endgroup\$ May 26 '13 at 9:16

Here is a direct link to a datasheet, since "alldatasheet.com" has gone offline.

If you look at the top of page 4, the parameter you're looking for is IOZ, output leakage current. It is given as ±0.5 µA typical at 25°C, ±5 µA worst-case over the commercial temperature range. This translates (assuming VCC = 5 V) to resistance values of 10 MΩ (typ.) and 1 MΩ (min.), respectively.


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