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MintyBoost voltage drops under load
Moderators: adafruit_support_bill, adafruit

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MintyBoost voltage drops under load

by vizzini on Thu Mar 06, 2014 10:17 pm

Without any load (i.e. no phone attached), the output voltage of my MintyBoost is 5.0V (+/- 0.03V or so) and the voltage on the D+ and D- pins is 2.0V. Since my iPhone wouldn't charge--I initially get the chime indicating it's charging, but then immediately I get the "This accessory may not be supported" message--I did some troubleshooting using a 15 ohm resistor as a load. With the resistor attached the output voltage of the MintyBoost drops to 3.1V even it I supply the MintyBoost 3.0V from a regulated bench power supply.

I checked and double-checked component placement and solder joints. Any suggestions on what to do next?

vizzini
 
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Re: MintyBoost voltage drops under load

by adafruit_support_bill on Fri Mar 07, 2014 6:49 am

even it I supply the MintyBoost 3.0V from a regulated bench power supply

What is the current rating of the bench supply? Measure the actual input voltage to the Minty under load.
If you post photos of the front and back of the board we can check over the assembly.

adafruit_support_bill
 
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Re: MintyBoost voltage drops under load

by vizzini on Fri Mar 07, 2014 9:20 pm

The bench supply is rated for 2.0A continuous. Voltage at the supply measures 3.01V powering only the MintyBoost; 2.99V with Minty under load.

MintyBoost_Top.jpg
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MIntyBoost_Bottom.jpg (519.62 KiB) Viewed 688 times

vizzini
 
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Re: MintyBoost voltage drops under load

by adafruit_support_bill on Fri Mar 07, 2014 9:30 pm

2A should be plenty on the input side, and the voltage drop is minimal Your assembly looks excellent too. I suspect either a bad chip or a marginal inductor. If you contact support@adafruit.com with a link to this thread we can send you a replacement MintyBoost kit.

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Please be positive and constructive with your questions and comments.