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I have a scenario in which one of two power sources is selected by a power multiplexing:

enter image description here

One solution is to use already existing mux ICs like TPS2115A. The problem is that the leakage of these ICs are relatively high for my application. For example, the leakage current when the input 1 is inactive is around 50uA which is quite high for an indoor solar power harvesting (unless if I'm missing a power mux IC with extremely low leakage).

I'm considering two possible solutions (which I'm not sure about):

1- Use a low leakage switch between the power source and the mux input 1 to limit the inactive leakage current:

enter image description here

The leakage of the switch could be far less than the leakage in mux IC. So when the switch is disabled it would limit the leakage current of the inactive input. To test if this solution is feasible, I manually added a reverse diode between power source 1 and input 1 in the inactive mode; it substantially reduced the leakage current without affecting the output (from source 2).

2- Getting rid of the power mux IC and have one switch for each power source:

enter image description here

I'm not sure if connecting two switches in this configuration is a good idea or not.

But I'd appreciate if anyone has had similar problem or has suggestions.

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  • \$\begingroup\$ Can you use relays ? If size isn't a problem. \$\endgroup\$
    – Long Pham
    Commented Jun 20, 2018 at 7:14
  • \$\begingroup\$ The leakage current still appears to be massively lower than what your load current would be (100 ohm shown in schematic). \$\endgroup\$
    – Andy aka
    Commented Jun 20, 2018 at 9:13
  • \$\begingroup\$ @Andy aka: You're right, but my problem is that the mux IC draws current from the sources even when they're not active. This prevents the sources from getting charged because a portion of the charging current leaks to the mux. \$\endgroup\$
    – vmontazeri
    Commented Jun 20, 2018 at 12:09
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    \$\begingroup\$ Leakage current is in the hundreds of nA typically @ 25'C. The operating current is much higher, tens of uA.. which are you concerned about? \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Jun 20, 2018 at 12:47
  • \$\begingroup\$ @SpehroPefhany I'm concerned about the operating current. Specifically, supply current from INPUT1 is around 75uA when it's inactive and INPUT 2 is the active source. This current is relatively high for my application. \$\endgroup\$
    – vmontazeri
    Commented Jun 20, 2018 at 16:07

1 Answer 1

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I just tried the second approach: used two switches one for each power source. The leakage is extremely lower than the multiplexer.

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  • \$\begingroup\$ Thanks for advice! Did you add some delay before switching on the first switch when switching off the second switch? And what ultra low leakage switches did you use? Some MOSFET? \$\endgroup\$
    – Foreen
    Commented Jul 13, 2022 at 10:43

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