LM25117-Q1: LM25117-Q1 digital controlling through PWM

Hello Bhargav,

One simple implementation to adjust VOUT of a Buck controller like the LM5117 is to use the LM10011.

Hope you find this device useful?

Kind regards,

David Baba.

Thanks David for the information. 

I had some other questions, the LM25117-Q1 (the typical application schematic). In the PDF of LM25117-Q1 (attached diagram). I wish to order all the components and for my application the range specified is similar to that in the Technical document. I wish to know if you can help with the values for the capacitors (e.g C24 to C31) which are stated as NU and that of the diodes also .

There is no specific set of values given in the datasheet for the application. The webench design has few capacitors and resistors but not the full application schematic as it is described in the datasheet. 

Regards 

Bhargav

Hello Bhargav,

For the Diode D1 use a 1N4148.
The Values of C24 to C31 will depend on your need for reducing the Vout Ripple and Transient performance of Vout. Typically they will not be needed unless you have a specific need to add based on the said Vout ripple and transient performance?
R7 is a 0ohm if you wish to boot strap supply the VCC Regulator from the output turning off the internal VCC regulator.
Z1 is used in place of R7 and is based on your Vout. It is used in case Vout>VCC Abs max voltage.
For example, if you have a Vout of 20V I would make Z1 = 10V which will supply 10V to the VCC pin of the device.

Let me know if you have any questions or concerns?

kind regard,

David.

Hello David, 

Thank you very much for the information on sch components. I am currently working on selecting the components, will ask for your assistance if there is any. 

Regards 

Bhargav 

Hello David, 

I am currently having few questions regarding using of LM10011 with LM25117-Q1, In my application as I wish to send the data, to CAN Bus and thus need a digital signal micro-controller dsPIC30F4011 in my Application. 

Can you suggest if the using LM10011 with other digital signal microcontrolller would be a good option. Or can I use some external circuitry and components to control the output of LM25117-Q1 ? along with dsPIC30F

Thank you 

Regards

Bhargav

Hello Bhargav,

I believe that the LM10011 would be a good option.

Please follow the guidelines in the datasheet to suit your requirements.

Let me know if you have a a more specific question regarding the LM10011?

Thanks.

David.

Hi david, 

Question regarding LM25117-Q1 is, for DC-DC power supply application purpose is it possible to use the schematic diagram provided in the data sheet of LM25117-Q1 

In my application I will have atmost 4 IC's (LM25117-Q1) 

In case I wish to limit the output current according to my application, which design should I go with, as there are 3 to 4 different LM25117-Q1 diagrams based on constant current and constant voltage regulator in the data sheet . 

Or the generalized application schematic which is that I had previously asked you (Q about the component selection) 

Regards 

Bhargav

Hello Bhargav,

 

The schematics in the datasheet are examples for specific Input, output voltages and output power.  I advise you use the Quick start calculator and/or WeBench to determine values in your design.

 

Regarding constant current and constant voltage control question, do you need current regulation, or just current limit?  If you need current regulation, what is your application?  Your application will determine the approach you move forward with.

 

Kind regards,

 

David.

Hi david, 

My application is I am currently working on a design (Design of Power supply to realize Automotive Transients for e.g Start-Stop System and so on 

The Plug-In module will have two ICs one buck-boost and other boost . Both this IC will have common input voltage but shall produce or give different output voltages dependent on the programmed ouput voltage through the digital signal Controller (dsPIC) which will control the output of this ICs.

The loads connected to this Power supply design are the loads connected to the ECU (Vehcile ECU). which will have different pins on which I need different current as per the load (at one pin 3A , 2A at the other and so on) 

For me it is important that I am able to measure this output current from LM25117-Q1 and am able to give some info to my controller regarding this output current..

So I feel going ahead with current regulation will be feasible .. I hope I have made things clear for you to understand my application. Is it possible to get this current value ? 

Regards 

Bhargav

hi David, 

I had a question, I have made a list of components that I will need for the power supply design with LM25117-Q1 and few other components in my design . Before proceeding for the actual PCB design with SMD components . I was thinking of using the through hole components for test design. Will using the through-hole components affect the LM25117-Q1 (if they are not Automotive qualified) ? Is it possible to work with them ?

Regards 

Bhargav 

Hello Bhargav,

Not sure I understand the question? Can you please clarify? Thank you.

David.

Hello, 

I meant when I open the design in webench there is a list of components which I need to use with the LM25117-Q1 for the design. The list says (all the components are automotive qualified) that is are capable of being used with the iC. This components are however all SMD components that is can be mounted on a designed PCB and not directly on a normal board. 

Before going for the actual PCB, I wish to get checked the components (passive capacitors and resistors some through-hole components). Do you think if they are not qualified for Automotive they can harm the IC LM25117-Q1? 

I hope I have made my question clear.

Thank you