# About the register description of MFR_CTRL_VOUT (D1h) of MPM3695

Dear Support member,
I am considering MPM3695-25.
I have a question about register descriptions.

Q1
Please tell me the meaning described in the description of MFR_CTRL_VOUT (D1h) on the data sheet p47.

Could you teach the meaning of the following description?
（Description）
00: Vo / Vref = 1, Vref = 0.5 ~ 0.672V,
LSB = 2mV

Best regard.

Hi,
The “00:Vo/Vref = 1” is referring to a 1:1 ratio where Vref=Vout if bits[1:0] is 00 for register D1h. The Vref and Vout can have a range of 0.5V to 0.672V with this setting.

Thank you very much for your answer.

Best regard.

Dear Cecilia

May I ask add a question?

Q2
Which of 01,10,11 is this register when the output voltage is 0.72V?

Best regard.

Hi Hideyuki,

I will have to get back to you on this since our engineer for this part is out of office for a few days. I have sent in the question and will let you know once I get a response.

Hi Hideyuki,
Please see below of the screen capture of Virtual Bench Pro 3.0 for MPM3695-25’s Vout Range choices for register D1h. Are you planning to use an external divider or use I2C to set the Vout?

Dear Cecilia

Thank you very much for your answer.
Is it possible to output 0.72V output voltage with an external resistor?

With external resistance, I think that the output voltage is up to 0.672V, and I am thinking of using I2C.

Best regard.

Hi Hideyuki,
Yes, it is possible to get 0.72Vout with an external FB divider. The D1h register [1:0] is changing the Vref, so it should allow for 0.72V output if it is set as 00.

Dear Cecilia,

Thank you very much for your answer.

May I ask add question?

previous your answer was
『The “00:Vo/Vref = 1” is referring to a 1:1 ratio where Vref=Vout if bits[1:0] is 00 for register D1h. The Vref and Vout can have a range of 0.5V to 0.672V with this setting.』.

Even on the capture screen, [0b00] is 0.5 to 0.672V.

Q3
How Is it possible to output 0.72V output voltage with an external resistor?

Q4
When outputting 0.72V output voltage with I2C,
Which of 01,10,11 is this register?

Best regard.

Hi Hideyuki,
Apologies for the conflicting info. I will have to contact the engineer that wrote that to clarify, but from what they said about the register, 00 should set only the Vref for 0.5V~0.672V.
To set 0.72V with an external FB, 00 should be used.
You can also follow the table below found in the evaluation board datasheet:

When outputting with I2C, it should be 01.

Dear Cecilia,

Thank you very much for your answer.
I really appreciate for checking.

Best regard.

Dear Cecilia,

Thank you very much for your answer.

May I ask add question?

Q5
What is the value of 0.5-0.672V of the external described in screen capture of Virtual Bench Pro 3.0?

Vout or Vref or VFB?

Q6
What is the value of 0.4 to 1.344V, 0.7 to 2.688V, and 1.3 to 5.376V of the internal described in screen capture of Virtual Bench Pro 3.0?

Vout or Vref or VFB?

Best regard.

Hi Hideyuki,

I am contacting internal to provide some insight on those questions.

Dear Cecilia,

Thank you very much for Correspondence.
This project is hurry.
When would you give me an answer?

Best regard.

Hi Hideyuki,
Please see response form our engineers below:
D1h’s[1:0] is to configure the divider according to the output voltage range. 00 is for external divider,”Vo/Vref=1” means”Vfb=Vref”
If you choose the range of 0.5~0.672V, then you can adjust the value of 29h and 21h to get a Vref. For more details, please refer to the datasheet.

Dear Cecilia,

Thank you very much for your answer.

May I ask add question?

I’m asking a question because I don’t know how to set the output voltage when using the internal setting resistor.

I don’t understand the relationship between VOUT_SCALE_LOOP(29h), VOUT_COMMAND(21h) and [1: 0] VO_RANGE of MFR_CTRL_VOUT (D1h).

Q7
Is it possible to set the output voltage by setting VOUT_SCALE_LOOP(29h) and VOUT_COMMAND(21h)?

[1: 0] Is VO_RANGE of MFR_CTRL_VOUT (D1h) unrelated to the output voltage setting?

Same question as last time, but
Q6-1
What is the value of 0.4 to 1.344V, 0.7 to 2.688V, and 1.3 to 5.376V of the internal described in screen capture of Virtual Bench Pro 3.0?

Vout or Vref or VFB?

Best regard.

Hi Hideyuki,
Can you please contact mpsnow@monolithicpower.com for further assistance? We can assign a local FAE that can further help you on this and can answer within your timezone.