I currently have a 2:1 switch / multiplexer which is being used to switch between two different batteries which are to provide power to a small module on my board. The switch that I am using is the TS5A3154 and I am wanting to switch between the channels using an output pin from my microcontroller (EFM32G222F128).
The issue that I am having is that the battery voltage is going to be approx. 2.7 – 3V which will be at both of the analogue inputs (NC and NO) and the supply voltage for this switch is going to be only 2.5 – 2.8V – due to V+ coming from a dual schottky diode which draws the current equally from each battery and also prevents on discharging through the other in the event of a battery failure so this part is needed.
Because of this small difference between the analogue inputs and V+, the Enable pin does not function properly (ie. when there is a high signal at the pin there is a high output when it should actually be off completely) and because of this I need to replace the switch with either a new component or a new solution which would only have a small voltage drop across it or be very low resistance.
I have already had a look around for alternative switches or multiplexers but it appears to me that the same problem would always be present for any alternatives that I looked at.
Low cost is also fairly important but at the moment I am more interested in any solution as opposed to a low cost one. The solution would also need to have a similar Enable function the current switch has in that the power to the module can be cut off at some point – either just by turning two separate things off or having one switch that would do it.
A schematic of what it currently is shown below might be of help for understanding a little more:
Best Answer
Why not use two devices then each can be powered by their individual local battery supply.
If not then TI have a range of power/load switches that may be suitable. I'm thinking of the TPS2080 listed on this page amongst other devices that may also be suitable. The TPS2080 is a dual supply with <0.1 ohms on resistance and supports a change over contact. It has a built-in charge pump that should overcome the problem you have.
If all else fails then create a low power "higher" voltage rail and use this for the chip supply.