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Powerboost 1000c , EN pin floating?
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Powerboost 1000c , EN pin floating?

by phinfinity on Fri May 19, 2017 9:48 pm

Hi,
I recently bought a powerboost 1000c to power my raspberry pi zero with a 3.7v LiPo. The boost worked perfectly initially but then flickered off (blue-light) and stopped voltage to 5V boosted pin for no apparent reason. Lot of fiddling around later, I was able to get it working again by connecting enable to Vsh pin. It looks like EN pin is floating and I couldn't get a stable 5V with it unconnected.

Is external pull-up to Vsh required with the EN pin or should the powerboost1000c normally work without external pullup? Am I doing something else wrong otherwise?

phinfinity
 
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Re: Powerboost 1000c , EN pin floating?

by adafruit_support_rick on Sat May 20, 2017 11:59 am

There's already a 200k pullup on the board itself. Hard to imagine it burning out or failing. Weird.

The resistor is here: Check for damage?
PB1000C_enable_pullup.png
PB1000C_enable_pullup.png (1.58 MiB) Viewed 126 times

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Re: Powerboost 1000c , EN pin floating?

by phinfinity on Sat May 20, 2017 4:28 pm

I disconnected my load from the board and tested the resistor with a multi-meter, it seems fine as it's still reporting 200k . After taking a closer look at the 1000c's diagram, I'm wondering if using load shared output along with 5v boosted separately could be an issue? I'm connecting a pi zero to 5v, and a separate load to Vsh (sim808 non-adafruit dev board). Would too much load via Vsh pin cause the pullup resistor to drop off ?

phinfinity
 
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Re: Powerboost 1000c , EN pin floating?

by adafruit_support_mike on Sat May 20, 2017 11:34 pm

Cell phone radios can use a lot of current when they talk to a cell tower.. the FONA's burst current is up around 2A.

Power to the Vsh pin is controlled by the MCP73871 LiPo charger's internal load-sharing circuit, which has an absolute upper limit of 1800mA. Combining a cell module's burst current with the current going to the boost converter may have damaged the MCP73871.

What voltage do you see on Vsh when running the PowerBoost from a 5v external source and from a LiPo?

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Please be positive and constructive with your questions and comments.