1
\$\begingroup\$

I am looking for a lowest V_f possible Schottky diode out there for logic circuits in my designs. So far the best thing I came across is MCL103. It has 200 mV of V_f at 1 mA current. I am not looking for a high current diode (10 mA top is fine) or high blocking voltage one (10 V is fine, although the higher the better). Lowest forward voltage is crucial. What do you use for this end?

Edit: the application: What I need the diodes for is simply to allow current flow only in one direction in glue logic circuits. Because of that, I need a cheap solution in a small form factor. Ideal diodes are too expensive and too big. For example, making an open drain like output from an push pull output, etc.

|improve this question
\$\endgroup\$
  • 2
    \$\begingroup\$ What is this being used for? You might just be able to use a PMOS which would get rid of that forward voltage altogether and basically replace it with a low value resistor. \$\endgroup\$ – DKNguyen Jan 3 at 19:26
  • \$\begingroup\$ You are likely not to find much better diode. Depending on what you are using it for, other solutions may be possible. \$\endgroup\$ – fraxinus Jan 3 at 19:34
  • \$\begingroup\$ "Lowest forward voltage is crucial." - why? \$\endgroup\$ – Bruce Abbott Jan 3 at 19:53
  • 1
    \$\begingroup\$ "For example, making an open drain like output from an push pull output" - what are the logic voltage levels? \$\endgroup\$ – Bruce Abbott Jan 3 at 23:53
  • 1
    \$\begingroup\$ Also what speed, and how much capacitance is acceptable? \$\endgroup\$ – Bruce Abbott Jan 3 at 23:57
3
\$\begingroup\$

Low forward voltage inherently means a lot of reverse leakage, particularly at high temperature. So there's not much in the way of free lunch.

If you only care about Vf at given current, pick a Schottky diode with the lowest voltage rating and highest current rating you can. For example, a 1N5817 has a typical Vf of 151mV at 1mA. There are surface-mount versions you can search for.

That said, perhaps there is a better way of doing whatever it is you are trying to do.

|improve this answer
\$\endgroup\$
  • \$\begingroup\$ Thank you for ansfer. I have edited the question. Your example is actually valid, but I didnt mention in the beginning that small form factor is important as well, since its for logic circuits usage purposes (dense ones). In this case high current diodes mean big diodes :/ \$\endgroup\$ – Bremen Jan 3 at 23:40
  • \$\begingroup\$ There are diodes available in SMT DO-216 that typically have 80mV forward drop at 10mA if you follow my suggestion on searching. But they leak -5mA at +50°C and 5V reverse voltage. \$\endgroup\$ – Spehro Pefhany Jan 4 at 0:14
  • 1
    \$\begingroup\$ Egads! Someone makes a device with that bad of specs? Limited to use, either low temp operation or else low reverse voltage operation or both, would seem to narrow the market a fair bit. \$\endgroup\$ – jonk Jan 4 at 10:27
2
\$\begingroup\$

I'd recommend first and foremost making sure you are not fighting the windmills (a.k.a XY-problem).

If after that you still need lowest possible forward drop, then google for "precision rectifier", "ideal diode" or "super diode". There are hundreds of options (like MAX40200 for example) at all the usual suppliers.

UPDATE:

OK, so you use diodes in "glue logic circuits". By definition "glue logic" connects active components (e.g. gates). Each such component will boost the logic signal to its output levels before passing it further, making your worries about voltage drops somewhat misplaced.

I can't imagine glue logic having more than 3-4 diodes in series (even that already screams for schematics revision). And since your currents are pretty low their forward drops will be minimal as well.

|improve this answer
\$\endgroup\$
  • \$\begingroup\$ Thanks for answer. I know the MAX40200 ideal diode chip (utiling it already in some designs). I have extended my ansfer to express the need better. \$\endgroup\$ – Bremen Jan 3 at 23:30
  • 1
    \$\begingroup\$ Updated the answer \$\endgroup\$ – Maple Jan 3 at 23:52

Not the answer you're looking for? Browse other questions tagged or ask your own question.