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Are there any other options for an extremely low loss switching circuit with extremely low switching frequency (about 4 times per day) and voltages from 0-3V with currents <2mA.

Current ideas include:

  • latching relays (<100mOhm, but use ~50mW for 5ms to switch) => would only consume power during switching, which is infrequent
  • analog signal switches (have about 100mOhm resistance and leakage/quiescent current in the tens of nA range) (eg. TI ts3a24159) => continuous quiescent power consumption

Does anyone have other solutions?

FYI: the switches are used in a "rectifier" that only changes the polarity of its input voltage about 4 times per day. It will be part of a TEG (thermal energy generator) that scavenges energy from a temperature difference and stores it in a battery. Since the temperature difference can be of both polarities the TEG will also output two different voltage polarities. So basically I want to minimize the total energy loss over a long period of time.

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  • \$\begingroup\$ What exactly do you care about? Conductance losses when the switch is closed, or power used by the switch? If the latter, why? \$\endgroup\$ – marcelm Apr 8 '16 at 15:15
  • \$\begingroup\$ Iq for the TI switch is 15na typically at room temperature. Is that really significant? If so, why? A battery probably has >100x that much self-discharge current. \$\endgroup\$ – Spehro Pefhany Apr 8 '16 at 15:28
  • \$\begingroup\$ @marcelm I care about the total losses in the system. Conductance losses are the main concern here, but if the power used by the switch itself is too large (for example with a regular relay) it too factors in heavily. It will be part of a TEG (thermal energy generator) that scavenges energy from a temperature difference and stores it in a battery. Since the temperature difference can be of both polarities the TEG will also output two different voltage polarities. So basically I want to minimize the total energy loss over a long period of time. \$\endgroup\$ – studentforlife Apr 10 '16 at 8:24
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Mosfets are another option. They're available with very low Rds(on), in the 10mOhm neighbourhood, and they require very little power to drive.

If your controlling voltage is low too, it might be tricky finding one with a low enough gate threshold voltage though.

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MOSFETs are indeed an option, and if you look around you can get P channel devices (easiest to switch because you need no boost circuit) with \$R_ds(on)\$ as low as 1.5 m\$\Omega\$ with 1.8V Vgs which is, quite honestly, astounding for a P channel device.

There does appear to be a mismatch between the page and datasheet, but I can certainly get P channel devices with about 3 m\$\Omega\$ from Vishay.

I am sure other vendors have suitable devices as well.

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