Hi, I would like to use a SMD device to boost a 3v battery to 5v with minimum passive components can anyone suggest an IC for the job ?
thanks
Andy
Yes, look at what Pololu has done here
CR2032 has a very limited capacity. What are you going to power by it?
It is a small thermometer that has a tilt switch when picked up it displays the temp on a .96" Oled for about 2 secs then the screen clears and the atmega328p returns to a deep sleep drawing 62uA. power is switched off to the DS18b temp sensor and the display via a transistor 2n2222a.
thanks
Andy
This boost module requires no external components and is SMD.
Thanks, this looks like just what I need!...will check it out some more.
I'd rather lower Atmega frequency to 8 MHz and feed your device directly from CR2032.
Seems unlikely that a CR2032 can supply enough current for an OLED display.
Most people recommend drawing no more from a CR2032 than 15 mA, but see this white paper on the topic.
Boosting to 5V will nearly double the current draw from the cell.
BJHenry:
This boost module requires no external components and is SMD.
Check the datasheet, a 4.7uf output cap is required. No matter, at $3 each and a uSiP package, it’s very DIY unfriendly.
andymouse:
Hi, I would like to use a SMD device to boost a 3v battery to 5v with minimum passive components can anyone suggest an IC for the job ?thanks
Andy
I'd rethink this, you aren't going to get enough power from a calculator cell, they are designed
for very low power operation and very long shelf life. There is a reason calculators use LCDs,
not LEDs, and that's because these 3V lithium coin cells are very low power.
Hi
The Oled I'm using has a maximum draw of about 20mA (measured) and the display is switched off most of the time, the Atmega 328p-AU is in "deep sleep" and draws 60uA, I'm wondering if that can be improved, but thats another topic ! So, my micro is in deep sleep and maybe a couple of times a day the project is picked up and activates a tilt switch that via a transistor (2N2222A) displays the temperature but only for a couple of seconds and then back to sleep. My problem is the Oled seems fine at about 4v but not much lower and I thought a dc-dc boost chip would solve it, otherwise all is well, I am using a DS18b20 as temp sensor. Any thoughts on this gratefully received otherwise bigger battery it is !
Andy
As mentioned, a CR2032 nor it’s big brother, the CR2450,, cannot handle the ~60ma draw when your device is operating. The CR2032 datasheet says the nominal discharge rate is 200ua. Running at more than 300 times that rate will not end well, not to mention rather quickly too! A 150mAh LiIon would happily handle the load for about the same physical size as a coin cell and anything larger in capacity would just add run time between charges.
Hi
Thanks, yes your right of course, and I will use your selection. I was getting hung up about size ( not for the first time ! ), in this case it matters ! Thanks for the links
Andy
CR2032 batteries have an internal resistance that normally limit them to around 30 mA. If you need 60 mA at 5V from a 2032, then you're looking at a non-starter. You may want to look at stacking 2032's if you really want to use those or perhaps a lithium ion battery.
andymouse:
My problem is the Oled seems fine at about 4v but not much lower and I thought a dc-dc boost chip would solve it, otherwise all is well, I am using a DS18b20 as temp sensor. Any thoughts on this gratefully received otherwise bigger battery it is !
Then its likley the OLED is designed for 5V operation and has a regulator on board to drop down to 3.3V.
I use the SSD1306 OLEDs on 3.3V, either the type without a regulator, or I remove it.
As ever, providing links to or details of the parts you are actually using is a great help to the forum.