TPS2117: TPS2117 how to select sources

Hossam Moghrabi

Intellectual 360 points

Part Number: TPS2117

Tool/software:

Hello,

I am interested in TPS2117 to have in my design.

the design is simple, i have 5v source and 3.3v source which i need to switch between them using a slide switch.

I need the switch to never short the 2 sources and only connect one.

the circuit I suggest is to have 5v go to IN1 and 3.3v go into IN2. MODE is connected to 5v all the time.

5v has a voltage divider of 1k || 1k resistors, which the divider is connected to PR1. please check the image below

high quality full res image here: https://slow.pics/c/ico5gzld

is this circuit fully working properly??

as seen, the switch has 2 positions: no connect and GND.

when at no connect, the resistor divider will stay the way it is delivering about 2.5v to PR1 which activates 5v.

when at GND, it will pull PR1 pin down to 0v which will disengage 5v and activates 3.3v.

is this correct?

should i use the circuit or does it need modification?

best regards

Hossam

over 1 year ago

0 Kunal Goel over 1 year ago

TI__Guru* 79181 points

Hi Hossam,

This implementation looks fine to me.

Regards

Kunal Goel

0 Hossam Moghrabi over 1 year ago in reply to Kunal Goel

Intellectual 360 points

hello,

thanks for your input.

in this case, what mode am i in? i believe it is priority mode not manual mode.

but how can i be in manual mode in my example? like, is it by connecting either 5v or gnd to PR1?

please explain

0 Kunal Goel over 1 year ago in reply to Hossam Moghrabi

TI__Guru* 79181 points

Hi Hossam,

Let me check on this.

Regards

Kunal Goel

0 Hossam Moghrabi over 1 year ago in reply to Kunal Goel

Intellectual 360 points

hello Kunal,

I am waiting for your analysis, thanks. I appreciate if you verify this via simulation or real hardware if you have a board for it.

the circuit i want is above, as you see it has 5v as main and 3.3v as aux supply. mode is tied to 5v and pr1 is tied to 5v via divider which delivers 2.5v... the switch when activated switches the pr1 pin to ground making it 0v which should disconnect 3.3v and activate 5v.

please respond in details about this circuit.

thanks

0 Kunal Goel over 1 year ago in reply to Hossam Moghrabi

TI__Guru* 79181 points

Hi Hossam,

Please see below:

If you see any issue on evaluation then we can take up replicating. Please see if you can test on EVM.

Regards

Kunal Goel

0 Hossam Moghrabi over 1 year ago in reply to Kunal Goel

Intellectual 360 points

So you affirm that I am operating in priority mode using schematic above.

also, manual mode is when i connect extra source to both MODE and PR1. however, if i have a gpio which is 5v and my source1 is 5v, wouldn't this mean the same to the IC?

anyway i am just interested in the schematic i provided up, please check and tell me if it will work exactly as I mentioned... which is when switch is off (to NC way) it is 5v and when switch is on (to GND way) it is 3.3v.

i appreciate if you simulate this since i don't have an evaluation board and will issue my product prototype board tonight.

0 Kunal Goel over 1 year ago in reply to Hossam Moghrabi

TI__Guru* 79181 points

I will get back soon on this.

0 Hossam Moghrabi over 1 year ago in reply to Kunal Goel

Intellectual 360 points

Hello,

still waiting your response.

however, i decided to go with this circuit to my prototype.

I am still skeptical about ST pin. I don't require or care about any indication thus I pulled it down to ground. I saw in datasheet mentioned that it "should be pulled high" but I don't want that.

will my circuit functions properly with ST pulled down to ground via 10k resistor? assuming I don't require any indication signal.

Here is the circuit for reference: https://imgur.com/gjgZpV9

https://imgur.com/gjgZpV9https://imgur.com/gjgZpV9https://imgur.com/gjgZpV9

please check the image and tell me if all ok.

thanks!

0 Kunal Goel 11 months ago in reply to Hossam Moghrabi

TI__Guru* 79181 points

Extremely sorry for late response. We had backlog of critical customer requests. Circuit looks fine. ST can be pulled low.

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TPS2117: TPS2117 how to select sources