Regulation Conundrum 2.8v

Go To Last Post
8 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I've been using these nice little TPS60100 Charge pump regulators for powering things from 3v batteries for a while. You put the chip, a couple capacitors and you've got a steady 3.3v as your battery goes from brand new to twice dead and plucked out by the roots.

 

However, these little TFT displays are always rated for 2.8v.

 

Does anybody know of a similar 2.8v regulator?

 

Perhaps I shouldn't worry about it and just run the TFTs at 3.3 anyhow?

 

I have 2 that have gone a little naf, and I'm wondering if 3.3v is doing them in. Likely, it's just me doing them in. A guy a NewHaven told me not to worry about it, but that was when they were working.

 

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Torby,

 

what is the maximum voltage the display can work at?

most of the time that is 3,3 or 3,6V, so you should be safe. if it is 3V then you could add a schottkey diode in series with the output of the TPS60100 this will drop the voltage with about 0,4V and then you should be safe.

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Most TFTs have a maximum 3.3V on their external pins.    But internally,   they use different voltages for the LCD contrast etc.

But the controller has several internal registers that determine the internal charge pumps.

 

You can ask it to measure its own supply voltage or you tell it that it is 2.8V or 3.3V or whatever.

 

I suggest that you use the controller facilities to measure / generate its voltages.

 

David.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Well, a little nervous as the max spec for the display is 3.3. Maybe I'll go with the diode, or just hope the TPS60100 doesn't run a little TOO high in its rated range.

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I didn't know about these parts, and just looked them up.  Nice.  What about the TPS60124/125 parts?  They output 3V, not 3.3, 200mA, and seem to be in the same price range.  Might they work, or am I missing something obvious?

 

http://www.ti.com/product/tps60124

Last Edited: Wed. Oct 15, 2014 - 10:17 PM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Nope. You're not missing anything, I was just missing those part numbers. Thanks!

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

http://www.pololu.com/product/2118

 

Not especially cheap, and probably too inefficient for your needs (0.3 mA quiescent), but there is a shutdown pin (30 µA at 3V).

"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"Wisdom is always wont to arrive late, and to be a little approximate on first possession."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Tom,

 

It is not step up, but I like using the TPS76333 as a 150mA, 3.3volt low drop out voltage regulator. I guess the TPS76328 would be the 2.8 volt unit. They have a 300 millivolt drop out voltage at 150mA.

 

Cheers,

 

Ross

Ross McKenzie ValuSoft Melbourne Australia