BBB (rev.0) Voltage drop

Interfacing hardware, sensors, output drivers, chips.
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LimesPone
Posts: 1
Joined: Fri Jan 06, 2017 7:03 pm

BBB (rev.0) Voltage drop

Post by LimesPone » Fri Jan 06, 2017 7:14 pm

Hi!

(Noob question below :oops: )

I have an older BBB rev.0 board, currently powered by the USB FTDI cable. At the FTDI cable pins, I read 5V. On the other side of the board, however, at the +5V/GND pins, I read ~3.57V. Is this drop expected?

(I should note also that I opted for a 7805a voltage regulator when constructing this board, years ago.)

The real issue that leads me to this question is that I'm trying to drive a chip that requires 4.75 to 11V supply voltage. So it seems that the voltage drop across the BBB results in a V that is outside of that range.

Thanks!

paul
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Posts: 706
Joined: Mon May 12, 2008 4:19 pm

Re: BBB (rev.0) Voltage drop

Post by paul » Sun Jan 15, 2017 2:15 pm

LimesPone,

The problem is the 7805, that voltage drop is about right for that device. Grab a more modern LDO such as a LM2940 or LM9931 (5v model) and put it in and you'll be fine. However you need to carefully check the inputs and outputs with a meter and compare to the pinout of the device you are putting in, to get it installed correctly.

Hope that helps,

Paul

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