Digital Potentiometer

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breaktru

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Instead of using an analog potentiometer for regulating the output voltage on a switched regulator or linear regulator, is there a Digital Pot that I can use instead?
This is NOT the part but is it something like this:
IC VOLTAGE DIVIDER DGLT 8-UMAX - MAX5420AEUA+
 

AttyPops

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Since you are looking on digikey, you probably have already seen digital pots...???....???....? or could just search for em. I'm not being smart, but my posting a link to digikeys digital pots is probably not what you are looking for. And since I haven't used em, I should probably not say anything but I did research em before. Some notes:

* Some have a memory so that they "remember" where they were last set and come back on at the same setting. This is some kind of flash memory with like 10,000 or 100,000 cycles. There is a procedure for setting it (a combination of high/low pins).

* Some have a +/- function to increase/decrease the resistance. Others work by digital communication to set the resistance (I2C, etc).

* they are often used with microcontrollers/MCUs... The MCU wants a digital interface so you don't have to rig a servo to turn a pot...lol.

* Many have 2-way communication so you can "read" the current setting of the pot.

* Lots of options for packages, resistances and capacities/ratings.

So I guess it depends, in part, on your intended interface.

Like I said, I've only done preliminary research and am still unsure of the details, but I hope this gets the conversation started.

Good Luck!

P.S. If you are using a mcu, there are other ways of varying resistance... like a resistor ladder of some sort with transistors, combination of pins/resistors sinking current, etc. ...... so you may not even need a digital pot. You may also wish to check out PWM of a power mosfet to see if that works for ya ... no need to vary resistance at all. IDK what you are designing so it's hard to comment.......

You'd think that someone would have a digital pot with 2 buttons built in ... plus and minus.... in a turn-key package. I haven't found one yet....
 
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SurvivorMcGyver

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Hey SurvivorMcGyver.... you know what that is??? THAT'S NIIIIIIICE!!!!

Simple 2 button interface.... auto storage... nice.

I thought so too -- Sorry I provided the link to one that that required a 4.5-5.5vcc - The one I've worked with from maxim (there are others) requires 2.7v - 5.25v - perfect for a single battery mod. I've played with some capacitive touch switches with it but have not implemented in in an actual mod yet (other than on a bread board). It has also been several months ago as I've been into other endeavors so there may be better more suitable units created since then. I have, however, set this aside as a definate go to for final design considerations. Pretty sweet - I think

That looks good SurvivorMcGyver. I think that maybe what I am looking for. Will do more research first. Thank you very much. Have you tried using something like that?

Only in simulations and bread boards as of yet -- sorry - no "real life History" -- but I can atest - It works as advertized - superbly -one I will most certainly implement when the circumstance calls for it.
 

rannox

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I just got a few samples of the 2.7-5.0v 1kohm version of these http://www.intersil.com/products/deviceinfo.asp?pn=X9317 to test out, but they are very, very, tiny, literally about 3mmx3mm (I got the msop instead of the pdip... oops).

Havent been able to test em out yet, waiting on some caps and momentary switches. Considering how tiny they are, ill get to learn how to drag solder... yay.... lol....
 

breaktru

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Can these Digital pots hold the amperage of an atty?

No, but they can handle the amperage of a control pin.

dig_pot1.gif

dig_pot2.gif
 

breaktru

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The majority of the digital pots are MAX voltage of 5.5 or 6v. The purpose of this project is to use it on a 7.4v evercool. I probably can tap it mid point for 3.7v.
I did find a 4.5v-8v but every site is sold out so somebody is buying them up. Maybe the Darwin guy. Also this D.P. can use either a single or two momentary switches for up and down resistance and is 10k ohm.
Has anyone used the previous mentioned? They are uMax packaged. I would need to find the machine from the fantastic voyage to shrink me and the iron to solder to it. The 8v one I found is a DIP package which I believe is maybe more practicle to solder to. I also found some SOIC packages and a video on how to solder them, also tiny format but I think larger than the uMax.
 

CapeCAD

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The maximum output adjust of the Evercool is 5.5V, why would you look for higher than that? You can add an external resistor between the Voadj pin and the pot to lower the max voltage the pot will see in the 2 terminal configuration. A minimum resistance of 240 Ohms is required according to the data sheet.
 
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breaktru

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Unless I can find a socket or PCB for these Ic's, the project is on hold. Tried solder to these micro chips yesterday with the smallest wire and smallest soldering tip and it was impossible for me to do it. I actually soldered four wires on when the pin 3 leg snapped off the IC. Rats....."#%* - %@ - ^ &#!#&"
 
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