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TPS2115A-Q1: TPS2115A-Q1 For Oring application

Stephen Thomas
Intellectual 710 points
Part Number: TPS2115A-Q1
Other Parts Discussed in Thread: TPS2115A

Hi,

I m looking for a low cost ORing solution (automotive qualified) that can be used for  5.V rail. 

i.e. I have two sources of 5V and I need provide output to the load from any one of them.

Idea is for redundancy with low voltage drop , I shall not loss the function due to a single regulator failure.

Current requirement is low (50mA)

Can TPS2115A-Q1  can be used for ORing application. I understand if both sources are 5V this will switch with 0.1 to 0.2V hysteresis. 

1. I m thinking that even if both the sources are within 0.1V tolerances the output will stick to either IN1 or IN2 and wait till 0.2V drop occurs in Auto mode. Please confirm

2.Can I use this in manual mode, i.e. I simply wire D1 to one of the 5V source so it will always select IN1 and if the 5V supply connected to D1 fails ( goes low <0.7V) output will automatically switch to IN2.

 Btw between VIH min (2V) and VIL max (0.7V) is it possible to know how the device may behave.

Thank you,

Regards

Stephen

  • 0
    TI__Mastermind 32650 points

    Hi Stephen,

    Do you have access to an TPS2115A EVM? I would recommend testing your system out on an EVM first.

    The TPS2115A is a PowerMUX and so it will be able to select one rail and pass to the output followed by the other in a break-before-make topology. Both your proposed cases are acceptable but they have different considerations/things to look out for.

    In case 1, the hysteresis is anywhere between 0.1V to 0.2V. What can occur here is that as the rails are loaded, the voltage could drop slightly causing the device to unintentionally switch to the other input. After this unloading, the rail could recover and rise up in voltage again. This in turn would cause another switchover. This depends on the current draw and the stability of the rails which is why I would first test this on an EVM.

    In case 2, I would use a resistor divider network that sets D1 to 2V as soon as IN1 rises to 5V rather than pulling D1 directly to 5V. The major concern here is that after IN1 has been disconnected, if there is significant input capacitance on this rail then it will take time for it to discharge. The pulldown on D1(from the resistor divider) has to pull D1 down below 0.7V quickly. Once again, this is system dependent and I would test this on an EVM first.

    Between 0.7V and 2V, the device behavior is not defined. Depending on the device, it could be ON, OFF or partially ON.

    We only have one automotive rated Power MUX offering at this time but we do have multiple automotive rated Load Switches. It is possible to build a PowerMUX using load switches. This is another option that you can pursue. Please refer to this tech document that describes building PowerMUXes with Load Switches: https://www.ti.com/lit/an/slva811a/slva811a.pdf