Suggestion on dual power source design

Jay Yeh

Other Parts Discussed in Thread: TPS62291, TPS63030, LM66100, TPS2121

I am now developing a system as the following figure, and the slave device part is what I am doing right now.

The slave device has a battery and could operate as a standalone device on its own.

The load electronics(MCU, Sensor, etc.) need 3.3v and 5v, so I use two regulators to have these two voltage supply.

The slave device could also connect to a host device. With different host devices, the host device could possibly provide 3v or 5v.

I would like to use the power provided by the host device while connected to share the current of the load system to extend the battery life of the slave device.

Could I naively connect the outputs of TPS63030 and TPS62291 together?

Thanks in advance.

over 5 years ago

0 Milos over 5 years ago

TI__Expert 7925 points

Hi Jay,

I would not recommend it, since both devices can sink the output current and operate in reverse, if they start fighting for control. The safest way would be to add ideal diodes. Or a switch on the TPS62291 output at least. When disabled, the TPS63030 disconnects the output from the input, which might not be the case for the TPS62291.

Best regards,
Milos

0 Jay Yeh over 5 years ago in reply to Milos

Intellectual 465 points

Hi Milos,

I added two LM66100 to the power block as the following figure:

Does it inline with what you suggested?

Will the output of two LM66100 still be 3.3V?

Would it effectively share the current load between the two 3.3v supply?

Thanks a lot.

0 Timothy Logan over 5 years ago in reply to Jay Yeh

TI__Mastermind 34935 points

Milos,

Generally it is not advised to use the LM66100 in a dual ORing configuration like then when both of the supply voltages are the same. The LM66100 is a make-before-break topology so if both supply voltages are the same there is a chance that the outputs will switch rapidly or both will be off. In this use case a power mux like the TPS2121 in a seamless switchover mode would likely be the better fit. See the below diagram taken from the datasheet:

There is also a really good TI design that explains a good switchover example similar to your scenario http://www.ti.com.cn/cn/lit/ug/tidue50/tidue50.pdf

0 Milos over 5 years ago in reply to Timothy Logan

TI__Expert 7925 points

Hi Timothy,

Thank you for the correction!

Best regards,
Milos

0 Tanvee over 5 years ago in reply to Milos

TI__Genius 17401 points

Hi Milos,

Yes, the TPS62291 device does not have a reverse current protection feature. The simple diode will help to protect to eliminate the reverse current here.

Best regards,

Tanvee

0 Jay Yeh over 5 years ago in reply to Timothy Logan

Intellectual 465 points

Hi Timothy,

Thanks for sharing the solution.

One little question that TPS2121 is a power mux, it should only use one input source at a time. Will it help to balance and share the current load between two input sources?

Thanks in advance.

0 Timothy Logan over 5 years ago in reply to Jay Yeh

TI__Mastermind 34935 points

Jay Yeh,

Maybe I am misunderstanding the application here- however the way the LM66100s are setup in the original diagram was an ORing configuration where only one supply was present at a time. The TPS2121 will be a similar operation where there is one primary supply and then the other auxillary supply is switched to once the primary supply falls below a certain voltage range. No supply balancing is done here.

0 Jay Yeh over 5 years ago in reply to Timothy Logan

Intellectual 465 points

Hi Timothy,

Any suggestion on the system design if the goal is to have load sharing?

Thanks in advance.

0 Timothy Logan over 5 years ago in reply to Jay Yeh

TI__Mastermind 34935 points

Jay Yeh,

I have moved this over to the load sharing forum and one of the engineers that work on our load sharing controllers may be able to give a suggestion.

Power management

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Suggestion on dual power source design