LM7480-Q1: LM7480-Q1 Usage for ORing 2 power supply - 5.3V

Kevin Slavinec

Part Number: LM7480-Q1
Other Parts Discussed in Thread: LM74800-Q1, LM5149

Hello,

We have arhitecture when we have primary and secundary power supply (both 5.3V) and we were wondering, if LM74800-Q1 would be suitable for our application? We would use reference design which is shown below.

Thanks, Kevin

10 months ago

0 Shiven Dhir 10 months ago

TI__Mastermind 20650 points

Hi Kevin

We are on timebank due to year-end and will get back to you after January 2, 2024. Sorry for the inconvenience...

0 Praveen GD 10 months ago

TI__Guru 57737 points

Hi Kevin,

What is the minimum voltage of the input power supplies ?

0 Kevin Slavinec 10 months ago in reply to Praveen GD

Prodigy 30 points

we have 2 different power supplies, 24V and 12V - battery power supplies, and then we are using LM5149 to set each of them to 5.3V for our device.

0 Praveen GD 10 months ago in reply to Kevin Slavinec

TI__Guru 57737 points

Hi Kevin,

Since the 5.3V is the output of a DC-DC converter, I am assuming the minimum voltage of this 5.3V rail is 5V.

For input voltage greater than 5V the LM74800-Q1 can output a gate-source voltage of minimum 10V to drive the FETs sufficiently into the linear mode.

So, yes you can use 2x LM74800-Q1 in Priority Power Muxing configuration as shown below for the 5.3V rails.

0 Kevin Slavinec 10 months ago in reply to Praveen GD

Prodigy 30 points

Hello Praveen,

great, thank you !

We will be using NTMFD5C680NLT1G for Q1/Q2/Q3/Q4 or do you suggest any other mosfet?

Also any recommendation for Q5 and D3?

0 Praveen GD 10 months ago in reply to Kevin Slavinec

TI__Guru 57737 points

Hi Kevin,

NTMFD5C680NLT1G FET looks good to me. You can select any Mosfet which satisfies the recommendations in the datasheet sections '10.2.4 MOSFET Selection: Blocking MOSFET Q1' and '10.2.5 MOSFET Selection: Hot-Swap MOSFET Q2'.

R5 and beta of Q5 can be adjusted to limit the current flowing from charge pump capacitor into Q4 FET gate. Q5 needs to be rated for 85V and should be able to handle only mA's of current. D3 allows turn OFF of Q4 by sinking current. D3 voltage rating can be 20V-30V and should be able to handle only mA's of current.

0 Kevin Slavinec 10 months ago in reply to Praveen GD

Prodigy 30 points

Thank you!

any suggestion for Q5? maybe PMSTA06,115?

0 Praveen GD 10 months ago in reply to Kevin Slavinec

TI__Guru 57737 points

Hi Kevin,

The 80V voltage rating of PMSTA06,115 is fine. You can consider using another transistor with higher beta.
PMSTA06 has a beta of 50 which makes the current flowing through the NPN collector and into the Q4 FET gate only 55uA x 50 = 2.75mA.
If you use a NPN with beta of 200, the the current into the Q4 gate can be 55uA x 200 = 11mA which means faster turn ON of Q4 during transition from VPRIMARY to VAUX

0 Kevin Slavinec 10 months ago in reply to Praveen GD

Prodigy 30 points

We will use BC816-25W. which has beta min 160 to max 450.

Thank you for help!

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LM7480-Q1: LM7480-Q1 Usage for ORing 2 power supply - 5.3V