Double MintyBoost not working

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tom42107
 
Posts: 3
Joined: Thu Jul 11, 2013 11:05 pm

Double MintyBoost not working

Post by tom42107 »

Hello, I decided to make a double MintyBoost, No reason really, just thought it might be cool. Well, it doesn't work. I've measured voltages and here is what I get:

Ground to Pin 1 of USB - 3.2v
to Pin 2 2.2v
to Pin 3 2.2v
This is the voltage readings on both of them so whatever I did wrong, I was consistent. Not sure what else to try. I know this isn't one of the MintyBoost kits so there might not be any way to help. Thanks for looking though.

Tom
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ifrpilot999
 
Posts: 26
Joined: Fri Nov 25, 2011 10:21 pm

Re: Double MintyBoost not working

Post by ifrpilot999 »

Looks like the chip is the LT1302CN8. The MB kit uses the LT1302CN8-5. The "-5" has resistors built in that set the output voltage to 5 volts. Not sure if there are other issues with the PCB, etc.

tom42107
 
Posts: 3
Joined: Thu Jul 11, 2013 11:05 pm

Re: Double MintyBoost not working

Post by tom42107 »

Thanks ifrpilot999. I've looked through all of the literature and datasheets and still can't find a difference between the CN8 and CN8-5. It's definitely worth a try. I'll see if I can get some samples. Thanks again.

Tom

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adafruit_support_bill
 
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Joined: Sat Feb 07, 2009 10:11 am

Re: Double MintyBoost not working

Post by adafruit_support_bill »

Ground to Pin 1 of USB - 3.2v
to Pin 2 2.2v
to Pin 3 2.2v
Hard to reconcile those measurements with the voltage divider in the schematic. Double check your measurements and component values.

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ifrpilot999
 
Posts: 26
Joined: Fri Nov 25, 2011 10:21 pm

Re: Double MintyBoost not working

Post by ifrpilot999 »

Tom -- Take a look at the datasheet, page 7, top right. "The LT1302-5 incorporates feedback resistors R1 and R2 into the device. Output voltage is set at 5.05V in Burst Mode, dropping to 4.97V in current mode."

Hope this helps. Also, Adadfruit support is the real BANNED master on this chip but usually only supports their kits builds. ;-)

tom42107
 
Posts: 3
Joined: Thu Jul 11, 2013 11:05 pm

Re: Double MintyBoost not working

Post by tom42107 »

Your right. after I posted that I couldn't see a difference I went back and found the part you referenced to. I'm sure the correct chip will clear up my problems. Thanks ifrpilot999.

Tom

Mopped
 
Posts: 3
Joined: Thu Feb 20, 2014 3:20 pm

Re: Double MintyBoost not working

Post by Mopped »

Does your circuit works?

Thanks
Mopped

Illum3415
 
Posts: 6
Joined: Sun May 11, 2014 12:09 pm

Re: Double MintyBoost not working

Post by Illum3415 »

Hello Tom,

Looking at your new boards there's a ton of usable space, perhaps you could incorporate a wider ground plane for pin 1 and 8 to enhance heatsinking. I hope you managed to find the error, otherwise the layout looks great.

Referencing: http://cds.linear.com/docs/en/datasheet/lt1302.pdf
PGND (Pin 8): Power Ground. Pins 8 and 1 should be connected under the package. In the SO package, pins 1 and 8 are thermally connected to the die. One square inch of PCB copper provides an adequate heat sink for the device.

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