Dual Power Supply selection

kamlesh patel

Other Parts Discussed in Thread: TPS25947

Dear All

I am designing a Design for Dual Power auto Selection for Load.

my main external source is a 12v Adapter and the secondary source is a 7.4V battery. I have a question regarding the below design as per below

1) when both power supplies are present then how much leakage current will pass through Mosfet to Battery due to Mosfet Body diode Leakage current ?.

2) What will be the effect of Reverse leakage current on the Battery when the Battery is fully 100% Charged ?.

3) is it really safe design ?.

4) How can overcome this Issue ?.

our main log is to save the Battery for a Long time.

Please suggest to me for Dual Power selection.

Thanks to All in Advance.

over 3 years ago

0 Kunal Goel over 3 years ago

TI__Guru 65295 points

Hi Kamlesh,

The implementation is based on discrete components which is generally bulky , high leakage current , poor thermal performance. Also when fet is enabled it will allow reverse current.

You can use new TPS25947 integrated FET device which is designed for ORing application(dual supply auto select). It is a low RON , always reverse current blocking device , 2mm*2mm package. Have a look at datasheet section 9.4 https://www.ti.com/lit/ds/symlink/tps25947.pdf?ts=1632999555146&ref_url=https%253A%252F%252Fwww.google.com%252F

Low leakage current:

Regards

Kunal Goel

0 kamlesh patel over 3 years ago in reply to Kunal Goel

Prodigy 120 points

Hi Kunal

Thanks for Reply

your suggested part is a very long lead time for production. so we can not wait as much.

we have first preferred power mux IC but due to the silicon crisis issue, we went for a Discrete Component solution.

So can you help us with our suggested Design. or any other solution for blocking reverse current from discrete components.

0 Kunal Goel over 3 years ago in reply to kamlesh patel

TI__Guru 65295 points

Hi Kamlesh,

I am expert on TI part. Best I can suggest is have a look at implementation in this app note in section 3. Your present configuration can allow reverse current as single FET is there. Back to Back FET have to be used.

https://www.ti.com/lit/an/slvae51a/slvae51a.pdf?ts=1634822315221&ref_url=https%253A%252F%252Fwww.google.com%252F

Regards

Kunal Goel

Power management

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Dual Power Supply selection