I want to improve an existing OFF/ON circuit in a project I have. Why do most off/on controller ICs have such a high quiescent current (approx 6 uA)? Their sole purpose is to manage an off/on battery circuit. The transistor I currently use has leakage of 100 nA.

I was looking at the MAX16054. I see they have a new lower power version (MAX16150) but it does not operate at the higher voltages. Other manufacturers seem to have the same limitations.

  • \$\begingroup\$ Why do you need a "controller" for that? Why not use a simple mechanical switch? With some de-bouncing cap? \$\endgroup\$ – Ale..chenski May 6 '19 at 17:41

6uA typ or even 20 uA max is not much “power”.

The Maxim IC’s you selected are designed for 5V logic only/

If you need high voltage low Quiescent current switches, you can choose MOSFETs or BJT’s to suit your task and choose low side switching for logic level drive.

If you define all your specs, for input and output V,I etc. Then you can start your design rather than look at IC’s and ask why these do not do the undefined tasks in your project.

Specs 1st, (must haves and nice to have for all inputs, outputs and environment)

  • then decide on topology, technology & find off-the-shelf solutions , figure out how it works,
  • then decide , Make or Buy.

This is how design is done.

P.s. all transistors have tradeoffs for V limit vs hFE vs GBW vs power rating vs leakage current vs slew rate vs current limit or Ron.

  • \$\begingroup\$ Thank you for explaining why they use that power. I don't expect you to put in all that work designing something for me. The voltage input is 6-10 V depending on the battery. logic is 3.3v from micro processor. Currently I use a FET isolated through an opto fet to turn power off and on from ether uP or an external button. My problem is it takes about 1 seccond for the uP to boot up and apply power to hold the fet on. so the operator needs to hold the power button for that 1 second. \$\endgroup\$ – instrumentek May 7 '19 at 16:39
  • \$\begingroup\$ I wanted to assess the feasibility of using a on/off push button controller IC to latch the input ON so the hold down time required is minimal. My battery pack is fairly large and 6uA would take quite some time to kill the battery. I just thought it was odd a basic FET leakage was much less in comparison \$\endgroup\$ – instrumentek May 7 '19 at 16:39
  • \$\begingroup\$ If you look at the IC schematic there is a lot more than a FET \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 7 '19 at 17:34

That's probably mostly the output driver at work: it has to be able to still pull the output below 0.4 V even if you draw 1.6 mA from it. That'll require a transistor that sinks 1.6 mA – and assuming a current amplification of say \$\beta\approx 200\$ that would roughly lead to your numbers.

  • \$\begingroup\$ the data sheet shows Supply: Current ICC VCC = 5V, IOUT = IOUT = 0, IN not connected 7 uA. I assumed that would be OFF state. no where in the datasheet can i find somthing that says OFF state current or quiescent current \$\endgroup\$ – instrumentek May 6 '19 at 15:37
  • \$\begingroup\$ yes, that's why I explained where the quiescent current comes from: There's an output transistor that keeps the output low. To do so, that transistor needs to have a base current. That's what I assume is what makes most of your 6 µA. \$\endgroup\$ – Marcus Müller May 7 '19 at 11:31

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