DC-DC Wandler mit MCP42010

[Bhargav Bharat J. (bhargavbharat_j)]

Hallo zusammen,

  ich arbeite zZ mit LM25117-Q1 ein dc-dc wandler (buck), damit möchte 
ich MCP42010 (digital POTI) ankopplen. Die MCP42010 ist ein 12 Pin IC 
(document und diagram im amhäng).

 Die Feedback output von die erste LM25117-Q1 dc-dc wandler soll ich mit 
dieser MCP42010 digi pot adjustieren. Ich bin nicht sicher aber welce 
PIN passt dass mit, ob mit die PW0, PW1 (die wiper output - feedback pin 
)

Wei soll ich den eigentlich die pinning ankloppen.


 Vielen Dank im Vorhaus!


 Bhargav

[Stefan F. (Gast)]

Ich verstehe dich nicht. Kannst das auf englisch besser schreiben? Dann 
mach das mal.

[Bhargav Bharat J. (bhargavbharat_j)]

Hi,

 English is better to explain,

 I am currently working on project design of power supply for Automotive

 This power supply is a switching mode power regulator

 The first SMPS IC "LM25117-Q1" 20 PIN IC  outputs positive voltage 
(upto
 40V), it has a FB pin with which I thought of using a digi 
Potentiometer to adjust the output voltage with its wiper resistance.

 It is 12PIN MCP42010 with SPI interface, which will be controlled by 
the

 dsPIC30f4011 controller (mit CAN ANSCHLUSS).

 My question is I am which pins should I used or connect the FB pin of 
my DC-DC converter with MCP42010 digi POT.

 I am currently creating this symbols in Ltspice so I can have a proper 
connections pin-pin

 Thanks

[Joachim B. (jar)]

muss er nicht, sinnverstehendes Lesen reicht


zum LM25117
https://www.mikrocontroller.net/attachment/349773/lm25117.pdf

Seite 1 Teiler Typical Application
Vout zu FB feedback dort ist das Poti die 2 R

MCP42010
http://ww1.microchip.com/downloads/en/devicedoc/11195c.pdf

Seite 11 Fig.2-25

PA0 (oder 1) ist Vout
PB0 (oder 1) ist GND
PW0 (oder 1) ist der Mittelpunkt zum FB feedback

[Stefan F. (Gast)]

I would prefer a DAC plus an OP-AMP instead of the digital 
potentiometer.

The DAC generates a programmable reference volatage. The OP-AMP compares 
that with the current output voltage. If the output voltage is too high, 
then the OP-AMP outputs a high voltage. If the output voltage is lower 
than it should be, then the OP_AMP outputs a low voltage.

The output of the OP-AMP is connected to the COMP input of the buck 
controller.

So that replaced the fixed internal reference voltage of the bock 
controller by an programmeable external one. As far as I know, it is 
important that the OP-AMP does not amplify the deviation too much, 
otherwise the circiut might oscillate.

Another similar approach without OP-AMP is described here: 
https://www.maximintegrated.com/en/app-notes/index.mvp/id/818

Another method with OP-AMP would be to generate the reference volate 
with PWM and a low-pass filter instead of a DAC.

[Bhargav Bharat J. (bhargavbharat_j)]

Thank you for your reply

  The thing is I have already the parts (Digital Potentiometer, MCP42010 
and
  also some other parts for the design.

  The approach of using a DAC can also be considered but the thing with 
DAC
  is I could not find them with SPI interface, with which I can use them 
with
  DSPIC30F4011 the controller in my design

  So, had to shift for the option of to use digi POT IC

  Bhargav