Ltc3888-1+mp86957

DC-DC Power Converters
1

Hello,

I would like to design multiphase power system which involves these two components.
However MP86957 looks promising, I dont understand why REFIN pin is missing in MPS SPS’s.
This is a voltage input pin controls Vcm of Iout pin.

there is a formula to calculate Vcm voltage. According to that formula

0.7<((Isw*Giout)*Riout)+Vcm<2.1

  • Vcm value is between 1.52-1.68 on LTC datasheet.
  • Giout is 5uA/A
  • Isw ~30A
    To calculate Riout
    0.7< ((30A*5uA/A)*Riout)+1.6<2.1
    Riout<~3.3k

So if I use a resistor below calculated value Can i achieve that missing pin problem ?
or is there a another solution can help me about REFIN pin problem ?

BR,
Mustafa.

2

Hi mstf.ozkan,

Thanks for your question.
From what I understand, it seems you can achieve your desired reference voltage (V_CM) with the equation you used from the datasheet. I checked your calculations and also calculated Riout </= 3.3Kohm.

Thanks,
Cindy

3

Hi Cindy,

Thanks for your reply.

I have another question. What If Isw=0A, will i get 1.6 Vcm on SPS’s Iout pin ?
I cant sure about it because there is too much gap 0<Rout<3k3 ohm.

BR,
Mustafa.

4

Yes, it depends on your reference voltage(V_CM) that is connected to I_OUT. I believe you stated in your original post that V_CM is 1.52-1.68V. So you should see that voltage if I_SW = 0A.

Cindy