Hello! We're designing a miniature air purifier in the wearables space. We're soliciting schematics (sketches are fine) to drive a dc fan with battery management, which you can post here, and as a community we can work toward a complete schematic. Tangent suggestions and tips also welcome!

$150 bounty (total) will be distributed via Paypal in 1-2 weeks to the most helpful posters.
Those posters may also receive an additional contract from us to finalize the schematic and proceed to layout / tapeout / testing.

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Parent Product
· miniature air purifier

Specs
· Adjustable 4.5-5.5V boost driver for DC fan, <200 mA
· Charging and protection for Li battery, 3.6V, around 300 mAh
· Button to turn on/off and adjust driver voltage (e.g. OFF -> 4.5V -> 5.5V -> OFF with button presses); also open to other UI suggestions
· PCB Footprint <300 mm^2 (not hard to do), 2 layers
* ~500 mA charging current

Consideration

* Battery safety and protection most important ! Otherwise user's face or hair might catch on fire...
* Design for mass manufacture
* Use only high volume standard components!
* Cost isn't critical if doing above ^
· No logic or RF blocks to worry about

 

Hello! We're designing a miniature air purifier in the wearables space. We're soliciting schematics (sketches are fine) to drive a dc fan with battery management, which you can post here, and as a community we can work toward a complete schematic. Tangent suggestions and tips also welcome!

$150 bounty (total) will be distributed via Paypal in 1-2 weeks to the most helpful posters.
Those posters may also receive an additional contract from us to finalize the schematic and proceed to layout / tapeout / testing.

=======================

Parent Product
· miniature air purifier

Specs
· Adjustable 4.5-5.5V boost driver for DC fan, <200 mA
· Charging and protection for Li battery, 3.6V, around 300 mAh
· Button to turn on/off and adjust driver voltage (e.g. OFF -> 4.5V -> 5.5V -> OFF with button presses); also open to other UI suggestions
· PCB Footprint <300 mm^2 (not hard to do), 2 layers
* ~500 mA charging current

Consideration

* Battery safety and protection most important ! Otherwise user's face or hair might catch on fire...
* Design for mass manufacture
* Use only high volume standard components!
* Cost isn't critical if doing above ^
· No logic or RF blocks to worry about

Couple of questions.
What is input voltage to charger.
Does it need to charge and run at the same time.
I assume the fan voltage is developed from the battery.
Fan voltage adjustable from 4.5 to 5.5 volts or is this tolerance?

Edit:
To speed things up, have a look at this IC.
http://cds.linear.com/docs/en/datasheet/3586fb.pdf

 

Thanks for the LTC3568 suggestion
It does the trick but it's a little expensive ($6 for small volumes)
How cheaply can you source it at scale?

Might be cheaper to source the charging IC and boost IC separately?

Addendum
* charge input is 5V via typical micro usb port
* battery 3.6V boosted to an user adjustable level (4.5V or 5.5V) for DC drive
* does need to charge and run at same time - matter of adding a FET switch?

 

Thanks for the LTC3568 suggestion
It does the trick but it's a little expensive ($6 for small volumes)
How cheaply can you source it at scale?

Might be cheaper to source the charging IC and boost IC separately?

Addendum
* charge input is 5V via typical micro usb port
* battery 3.6V boosted to an user adjustable level (4.5V or 5.5V) for DC drive
* does need to charge and run at same time - matter of adding a FET switch?

Okay. VW not Mercedes.
How about BQ1040 and AP3012. About $1 in 100's.
Find here.

 

...
$150 bounty (total) will be distributed via Paypal in 1-2 weeks to the most helpful posters.
...

You guys are trying to do this on the cheap side I see. $150.00 is chicken feed for an experienced engineer and represents about an hours worth of effort. Most of us would help you for free, now that we are retired. Why do you feel the need to make such an insulting offer for our valuable skill and experience. Take your money and put it in a dark place where the sun does not shine.

 

This post also rubs me the wrong way.

 

This post also rubs me the wrong way.

Yea, I don't think anyone wants his money, but it is a welcome chance from LED circuits.

 

You guys are trying to do this on the cheap side I see. $150.00 is chicken feed for an experienced engineer and represents about an hours worth of effort. Most of us would help you for free, now that we are retired. Why do you feel the need to make such an insulting offer for our valuable skill and experience. Take your money and put it in a dark place where the sun does not shine.

This post also rubs me the wrong way.

I'd like to apologize if my offer was insulting to you.
We were asking for schematic suggestions, not complete designs.
My thinking was maybe I get parts suggestions and then I can draft a schematic to be reviewed and then iterate--not meant to take too much of anyone's time.

Again my apologies, and all the best.

 

I'd like to apologize if my offer was insulting to you.
We were asking for schematic suggestions, not complete designs.
My thinking was maybe I get parts suggestions and then I can draft a schematic to be reviewed and then iterate--not meant to take too much of anyone's time.

Again my apologies, and all the best.

Did you have a look at the parts in post #4?

 

Thanks ronv.
AP3012 looks good but what's BQ1040 (couldn't find it anywhere)?

Attached is my schematic draft so far w ap3012
Need charging and run at same time; what's the typical setup here?

 

I think in general it's ok to charge and load the battery simultaneously
Just wondering why some charging pmics specifically tell you to decouple the load while charging (maybe if load is big or variable and messes with vsense on the charger?)

 

I think in general it's ok to charge and load the battery simultaneously
Just wondering why some charging pmics specifically tell you to decouple the load while charging (maybe if load is big or variable and messes with vsense on the charger?)

Sorry about the typo. The number for the other IC is BQ21040.
I think the only things you need to worry about is that the charger ic can supply enough current to both charge and supply the load and do it before any safety timer goes off.