LM25149-Q1: Question about VCC regulator

Yuta Kurimoto

Part Number: LM25149-Q1

Hello Team,

Our customer is now considering to use TPS25149-Q1. They have some questions about VCC regulator inside this device.

Q. How much is the RON(max) of FET inside the VCC regulator?

Q, Could you describe what is "RVCCX(VCCX resistance)=2Ω)"? Is this external resistor? I would like you to describe this resistance in the circuit diagram for my better understanding.

FYI, Customer usecase are below

・Vin=4V~36V(Load dump)

・Vout=3.3V

・Iout=23.5A

・Fsw=500kHz

Thanks,

Yuta Kurimoto

over 2 years ago

+1 Timothy Hegarty over 2 years ago

TI__Mastermind 49647 points

Kurimoto-san,

Q1: We need to check this parameter - do you need it at room temp or at hot?

Q2: This is the resistance of the switch that connects VCC to VCCX. Note, however, that a 3.3V output is too low to power VCCX (the changeover threshold is 4.3V).

Regards,

Tim

0 Yuta Kurimoto over 2 years ago in reply to Timothy Hegarty

TI__Expert 8290 points

Hello Tim,

Thanks for your answer.

For the Q1, they need the RON(max) at hot temp(Tj=125C).

Regards,

Yuta Kurimoto

+1 Orlando Murray over 2 years ago in reply to Yuta Kurimoto

TI__Mastermind 22299 points

Hi Yuta,

You can use 0.5Ω as a starting point for the RDSON of the VCC LDO.

We don't have data over temperature for that parameter.

Let me know if you have further questions.

Power management

Power management forum

LM25149-Q1: Question about VCC regulator