Logic IC required

Hello Abhishek,

In this case, what do you mean by isolate? Do you mean that you need them to have separate ground paths altogether, or do you just mean you need to make sure they aren't shorted together?
Are you saying that you need a device that chooses between two power sources to supply to another part of the system?
Logic devices are not a good way to source power, but they can be a good way to control where power is sourced from.

Do you need a power ORing type setup where the higher voltage is always provided to the system?
For example you could use a diode power ORing type structure to preferentially source current from the supply that has a higher voltage.

Also, do you have a signal to control which power supply you want to be active? Its possible you could use some sort of Logic device to input into a controller that drives one of two FETs to provide current specifically from that source.

What are the current requirements for your power source?
Any additional information you could provide would be very helpful.

Best,
Michael

Hi Michael,

Thanks for your reply. Below are my replies is red.

In this case, what do you mean by isolate? Do you mean that you need them to have separate ground paths altogether, or do you just mean you need to make sure they aren't shorted together? --> By Isolated I mean independent of each other, Ground is common for both of the supplies.
Are you saying that you need a device that chooses between two power sources to supply to another part of the system? --> Yes I mean a device which chooses between two power sources  but its in the same system. In my application hardware there is a Micro USB port which is source of 3.3V power supply (through a 5V to 3.3 V buck) and another is the main board power supply giving 3.3V  to a application circuit. I want the application circuit to be powered by either of them in either's presence and in the case of both of the power sources present, priority should be given to the main board supply, also ensuring that the both these supplies get a short connection.

Do you need a power ORing type setup where the higher voltage is always provided to the system?
For example you could use a diode power ORing type structure to preferentially source current from the supply that has a higher voltage. --> Nope, both of the voltages are same value, just need priority to be given to one of them when both are present.

Also, do you have a signal to control which power supply you want to be active? Its possible you could use some sort of Logic device to input into a controller that drives one of two FETs to provide current specifically from that source.--> I dont have a signal source to control it. this has to be a passive selection system, the solution IC should not operate on any kind of Vcc supply, because the sources themselves have to be selected by this IC ! 

What are the current requirements for your power source? -->500mA, 3.3V is my requirement

Thanks

Abhishek

Hi Abhishek,

Have you taken a look at the TPS211x devices? These devices are integrated power muxes and may fit in your application.

Another option would be using load switches or eFuses to solve this. Here's an app note which can give you more information.

Thanks,

Alek Kaknevicius

Hi Alek,

Thanks for the device's  suggestion.

I am employing a TPS2080D device in my design as TPS211x seems little costly for my design.

Though its a bidirectional device but I am making use of it by providing a complementary enable logic to the other pin with the help of transistor.

I hope this works

I

Hope this works.

What do you say ?

Thanks

Abhishek

Hi Michael,

Thanks for that suggestion. Not taking any chances I am going with TPS2111A solution with below schematics.

Please give your feedback.

Thanks

Abhishek

Hi Abhishek,

Based on the schematic, it looks like you have configured an automatic switching priority mux with priority to IN1 which will follow the truth table in the image.

Is D0 left floating or will it be pulled up?

Thanks,

Alek Kaknevicius

Hi Alek,

Yes, I have given priority to IN1.

D0 is left floating, I referred to the datasheet of TPS2111A page 16 Fig. 14, which describes this circuit.

DO let me know your feedback on the same.

Thanks

Abhishek