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I am looking for a ultra low voltage 2 ch stereo analog switch. I have two headphone audio sources that I need to switch between. It is very important that the chip can run of a 1.2v rechargeable cell (900 mAh) and use very low current.

I have been looking in digikey, intersil and maxim but all I can find are using a minimum single 1.8 V supply, which is to high.

My hopes are to avoid a DC-DC converter on this high quality audio device. The device currently has a run time of 30 hours on a 1.5v alkaline battery.

EDIT: I check around for relays to use in order to make the mechanical solution, and a 1.5V driven relay use a lot of current which in my case is not a acceptable solution. And I didn't find any 1V relays as well.

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    \$\begingroup\$ What is the voltage range of the audio signal? It appears you want the switch to run from 0 to 1.2V control, but headphone audio signals can easily be more than that peak to peak. \$\endgroup\$ – Olin Lathrop Nov 7 '11 at 15:00
  • \$\begingroup\$ I was looking at the MAX4745 and I think it can handle an audio source with a peak to peak higher than VCC but please correct me as I am no eagle to read datasheets. The problem is that it still has a minimal VCC of 1.8v. \$\endgroup\$ – Benjamin Nov 8 '11 at 0:19
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    \$\begingroup\$ If the only supplies you have are 0 and 1.2V, it's not a high-quality audio device. \$\endgroup\$ – Connor Wolf Nov 8 '11 at 3:47
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Your options basically fall into two broad catagories: Some sort of semiconductor device, like an opamp or analog CMOS switch, or some sort of mechanical switch (a.k.a. relay).

The problem with using a semiconductor device is that you really want your power rail to be higher than the audio. For a headphone that would put your power rail somewhere in the +/- 5 to 12v range.

A latching relay would be nice, and they are available. I doubt that you can find one that works at 1.2v, but it would only consume power when actually switching. A DC/DC converter might be required, but it only has to be on when switching the relay. Plus, it is very hard to beat the audio quality of what's effectively a piece of wire.

Of course, let me ask the obvious question: What's the problem with a simple switch? Zero power consumption. No power rail issues. Super reliable. Great sound quality. If a simple switch will work then this is what you want to use.

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  • \$\begingroup\$ The relay is a nice idea, but I am looking for a low power, low supply voltage chip that will still operate even so that the alkaline or rechargable battery voltage drops 1.5V/1.2V. \$\endgroup\$ – Benjamin Nov 8 '11 at 0:23
  • \$\begingroup\$ @user861389 It seems to me that David has explained how a relay can be low power/low supply voltage. If you want more then that you will really need to explain more about what you are doing and why a simple switch wont work. \$\endgroup\$ – Kellenjb Nov 8 '11 at 1:16
  • \$\begingroup\$ @user861389 To use something other than a switch/relay you must have your power be a higher voltage than the peak audio level. Sometimes higher by several volts. This is true of the MAX4745-- listed as "analog signal range" in the datasheet. If your requirements are: super low power, no DC/DC converter, and high audio quality then a latching relay is the only thing that fits the bill. If that still doesn't work then you will either have to loosen your requirements or tell us much more about your application. \$\endgroup\$ – user3624 Nov 8 '11 at 2:00
  • \$\begingroup\$ @DavidKessner Ok I see, so when the MAX4745 operate at 1.8v it can only handle a audio signal lower than the 1.8V ? \$\endgroup\$ – Benjamin Nov 8 '11 at 8:47
  • \$\begingroup\$ @DavidKessner thank you for making me think about the relay option again. \$\endgroup\$ – Benjamin Nov 8 '11 at 9:14
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A latching relay might be an interesting solution, though you might have to rewind the coil yourself.

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